Environmental Biology

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CHAPTER 1

Teaching classification of Plants and Animals

Historical Background

People who live close to nature usually have an excellent working knowledge of the elements of the local fauna and flora important to them and also often recognize many of the larger groups of living things (e.g., fishes, birds, and mammals). Their knowledge, however, is according to need, and such people generalize only rarely.

However, some of the earliest forays into formal, but limited, classification were undertaken by the ancient Chinese and ancient Egyptians. In China a catalog of 365 species of medicinal plants became the basis of later hydrological studies. Although the catalog is attributed to the mythical Chinese emperor Shennong who lived about 2700 BCE, the catalog was likely written about the beginning of the first millennium CE. Similarly, ancient Egyptian medical papyri dating from 1700 to 1600 BCE provided descriptions of various medicinal plants, along with directions on how they could be used to treat illnesses and injuries.

From the Greeks to the Renaissance

The first great generalizer in Western classification was Aristotle, who virtually invented the science of logic, of which for 2,000 years classification was a part. Greeks had constant contact with the sea and marine life, and Aristotle seems to have studied it intensively during his stay on the island of Lesbos. In his writings, he described a large number of natural groups, and, although he ranked them from simple to complex, his order was not an evolutionary one. He was far ahead of his time, however, in separating invertebrate animals into different groups and was aware that whales, dolphins, and porpoises had mammalian characters and were not fish. Lacking the microscope, he could not, of course, deal with the minute forms of life.

The Aristotelian method dominated classification until the 19th century. His scheme was, in effect, that the classification of a living thing by its nature—i.e., what it really is, as against superficial resemblances—requires the examination of many specimens, the discarding of variable characters (since they must be accidental, not essential), and the establishment of constant characters. These can then be used to develop a definition that states the essence of the living thing—what makes it what it is and thus cannot be altered; the essence is, of course, immutable especially geometry, which fascinated the Greeks. Mathematics seemed to them the type and exemplar of perfect knowledge, since its deductions from axioms were certain and its definitions perfect, irrespective of whether a perfect geometrical figure could ever be drawn. But the Aristotelian procedure applied to living things is not by deduction from stated and known axioms; rather, it is by induction from observed examples and thus does not lead to the immutable essence but to a lexical definition. Although it provided for centuries a procedure for attempting to define living things by careful analysis, it neglected the variation of living things. It is of interest that the few people who understood Charles Darwin’s Origin of Species in the mid-19th century were empiricists who did not believe in an essence of each form.

Aristotle and his pupil in botany, Theophrastus, had no notable successors for 1,400 years. In about the 12th century CE, botanical works necessary to medicine began to contain accurate illustrations of plants, and a few began to arrange similar plants together. Encyclopaedists also began to bring together classical wisdom and some contemporary observations. The first flowering of the Renaissance in biology produced, in 1543, Andreas Vesalius’s treatise on human anatomy and, in 1545, the first university botanic garden, founded in Padua, Italy. After this time, work in botany and zoology flourished. John Ray summarized in the late 17th century the available systematic knowledge, with useful classifications. He distinguished the monocotyledonous plants from the dicotyledonous ones in 1703, recognized the true affinities of the whales, and gave a workable definition of the species concept, which had already become the basic unit of biological classification. He tempered the Aristotelian logic of classification with empirical observation.

 

Aristotle, Greek Aristotle, (born 384 bc, Stagira, Chalcidice, Greece—died 322, Chalcis, Euboea), ancient Greek philosopher and scientist. The Greeks had constant contact with the sea and marine life, and Aristole, seems to have studied it intensively during his stay on the island of Lesbos. In his writings, he described a large number of natural groups, and, although he ranked them from simple to complex, his order was not an evolutionary one. He was far ahead of his time in separating invertebrate animals into different groups and was aware that whales, dolphins, and porpoises had mammalian characters and were not fish. Lacking the microscope, he could not, of course, deal with the minute forms of life. The Aristotelian method dominated classification until the 19th century. His scheme was, in effect, that the classification of a living thing by its nature .As against superficial resemblances requires the examination of many specimens, the discarding of variable characters (since they must be accidental, not essential), and the establishment of constant characters. These can then be used to develop a definition that states the essence of the living thing. The model for this procedure is to be seen in mathematics, especially geometry, which fascinated the Greeks. Mathematics seemed to them the type and exemplar of perfect knowledge since its deductions from axioms were certain and its definitions perfect, irrespective of whether a perfect geometrical figure could ever be drawn The biological classification of plants and animals was first proposed by Aristotle, who virtually invented the science of logic, of which for 2,000 years classification was a part of. Greek Aristotles, (born 384 bc, Stagira, Chalcidice, Greece—died 322, Chalcis, Euboea), ancient Greek philosopher and scientist. The Greeks had constant contact with the sea and marine life, and Aristole, seems to have studied it intensively during his stay on the island of Lesbos. In his writings, he described a large number of natural groups, and, although he ranked them from simple to complex, his order was not an evolutionary one. He was far ahead of his time in separating invertebrate animals into different groups  was aware that whales, dolphins, and porpoises had mammalian characters and were not fish. Lacking the microscope, he could not, of course, deal with the minute forms of life. The Aristotelian method dominated classification until the 19th century. His scheme was, in effect, that the classification of a living thing by its nature. As against superficial resemblances requires the examination of many specimens, the discarding of variable characters (since they must be accidental, not essential), and the establishment of constant characters. These can then be used to develop a definition that states the essence of the living thing.

The model for this procedure is to be seen in mathematics, especially geometry, which fascinated the Greeks. Mathematics seemed to them the type and exemplar of perfect knowledge since its deductions from axioms were certain and its definitions perfect, irrespective of whether a perfect geometrical figure could ever be drawn Aristotle, Greek Aristotle, (born 384 bc, Stagira, Chalcidice, Greece—died 322, Chalcis, Euboea), ancient Greek philosopher and scientist. The Greeks had constant contact with the sea and marine life, and Aristole, seems to have studied it intensively during his stay on the island of Lesbos. In his writings, he described a large number of natural groups, and, although he ranked them from simple to complex, his order was not an evolutionary one. He was far ahead of his time in separating invertebrate animals into different groups and was aware that whales, dolphins, and porpoises had mammalian characters and were not fish. Lacking the microscope, he could not, of course, deal with the minute forms of life. The Aristotelian method dominated classification until the 19th century. His scheme was, in effect, that the classification of a living thing by its nature. As against superficial resemblances requires the examination of many specimens, the discarding of variable characters (since they must be accidental, not essential), and the establishment of constant characters. These can then be used to develop a definition that states the essence of the living thing. The model for this procedure is to be seen in mathematics, especially geometry, which fascinated the Greeks. Mathematics seemed to them the type and exemplar of perfect knowledge since its deductions from axioms were certain and its definitions perfect, irrespective of whether a perfect geometrical figure could ever be drawn. But the Aristotelian procedure applied to living things and is not by deduction from stated and known axioms Rather, it is by induction from observed examples and thus does not lead to the immutable essence but to a lexical definition. Theophrastus of Lesbos (c.371-c.287 BC), Greek  philosopher Known as the “father of botany” Theophrastus described  over 500 plant species and devised an advanced classification scheme for plants. Artwork from the 19th century book Vies des Savants Illustres. Aristotle and his pupil in botany, Theophrastus, had no notable successors for 1,400 years. In about the 12th century CE, botanical works necessary to medicine began to contain accurate illustrations of plants, and a few began to arrange similar plants together. Encyclopaedists also began to bring together classical wisdom and some contemporary observations. The first flowering of the Renaissance in biology produced, in 1543, Andreas Vesalius’s treatise on human anatomy and, in 1545, the first university botanic garden, founded in Padua, Italy. After this time, work in botany and zoology flourished. John Ray summarized in the late 17th century the available systematic knowledge, with useful classifications. He distinguished the monocotyledonous plants from the dicotyledonous ones in 1703.He recognized the true affinities of the whales and gave a workable definition of the species concept, which had already become the basic unit of biological classification. He tempered the Aristotelian logic of classification with empirical observation.

few people who understood Charles Darwin’s origin of species in the mid-19th century were empiricists who did not believe in essence of each form.

The main criteria of the kingdom classification are cell structure, body organization, mode of nutrition and reproduction, and phylogenetic relationships based on the evolutionary development and diversification of a species. At present, the biological classifications include Greek Aristotle, (born 384 BC, Stagira, Chalcidice, Greece—died 322, Chalcis, Euboea), ancient Greek philosopher and scientist. The Greeks had constant contact with the sea and marine life, and Aristotle, seems to have studied it intensively during his stay on the island of Lesbos. In his writings, he described a large number of natural groups, and, although he ranked them from simple to complex, his order was not an evolutionary one. He was far ahead of his time in separating invertebrate animals into different groups and was aware that whales, dolphins, and porpoises had mammalian characters and were not fish. Lacking the microscope, he could not, of course, deal with the minute forms of life. The Aristotelian method dominated classification until the 19th century. His scheme was, in effect, that the classification of a living thing by its nature. As against superficial resemblances requires the examination of many specimens, the discarding of variable characters (since they must be accidental, not essential), and the establishment of constant characters. These can then be used to develop a definition that states the essence of the living thing. The model for this procedure is to be seen in mathematics, especially geometry, which fascinated the Greeks. Mathematics seemed to them the type and exemplar of perfect knowledge since its deductions from axioms were certain and its definitions perfect, irrespective of whether a perfect geometrical figure could ever be drawn as Viruses, Viroids and Lichens.

 

Taxonomy

 The term is derived from the Greek taxis (“arrangement”) and nomos (“law”). Taxonomy is, therefore, the methodology and principles of systematic botany and zoology and sets up arrangements of the kinds of plants and animals in hierarchies of superior and subordinate groups.

 

Popularly, classifications of living organisms arise according to need and are often superficial. Anglo-Saxon terms such as worm and fish have been used to refer, respectively, to any creeping things including, snake, earthworm, intestinal parasite, or dragon and to any swimming or aquatic thing. Although the term fish is common to the names shellfish, crayfish, and starfish, there are more anatomical differences between a shellfish and a starfish than there are between a bony fish and a man. Vernacular names vary widely. The American robin (Turdus migratorius), for example, is not the English robin (Erithacus rubecula), and the mountain ash (Sorbus) has only a superficial resemblance to true ash. Biologists, however, have attempted to view all living organisms with equal thoroughness and thus have devised a formal classification. A formal classification provides the basis for a relatively uniform and internationally understood nomenclature,

A hierarchical system is used for classifying organisms to the species level. This system is called taxonomic classification. The broadest classifications are by domain and kingdom. The most specific classification is by genus and species. The hierarchical groupings in between include phylum, class, family, and order. Species are the basic unit of classification. While there are different views on what defines a species, in sexually reproducing organisms, a species has traditionally been defined by the ability of its members to reproduce together to form fertile offspring. This definition is trickier in asexually reproducing organisms like bacteria, archaea, and protists, where scientists look at the similarity in DNA among individuals to tell whether they are in the same “species

Biological Classification: Plant and Animal Kingdom

In 1969, R.H. Whittaker defined five kingdoms   as Monera, Protista, Fungi, Plantae and Animalia. The main criteria based on which classification was done, are cell structure, mode of nutrition, reproduction and phylogenetic relationships.

Over time, an attempt has been made to evolve a classification system which reflects not only the morphological, physiological and reproductive similarities, but is also phylogenetic. That is based on evolutionary relationships. The Kingdoms Plantae and Animalia, commonly called to as plant and animal kingdoms, respectively.

 

 

Plant Kingdom

Living organisms have an organized structure, and have increasing levels of complexity from molecules to cells and tissues to integrated systems of organs. This is evident in the cellular structure and organization of plants and repeated over and over in the development of shoot and flower buds and root primordial. Living organisms require energy to survive. Virtually all plants do photosynthesis which provides their own chemical energy. Then, it is stored as carbohydrate fuel. All living organisms are dependent on this photosynthetic product for their energy source.

Plants must do cellular respiration, the process that converts the fuel molecules to the energy needed to do cell work, just as all organisms must. These chemical pathways are virtually the same in all organisms. Plants have metabolic dependence on water. Plants have means of conserving water. Plants use water pressure to maintain strength in soft tissues. Plants use water pressure to promote elongation and cell growth. Water is the transport medium for plant nutrients throughout the plant body.

There is a great reproductive versatility in plants. Many plants reproduce both asexually and sexually. As plants evolved, dispersal via seeds versus spores provides energy to start for establishing new plants as well as protection for the embryonic plant. In addition, plants have evolved means to ensure successful sexual reproduction in the absence of mobility and means of dispersing young to

Animal

Every members of Animalia are multicellular. Sponges have, loose cell aggregates arrangement. They exhibit cellular level of organization. In coelenterates, the arrangement of cells is more complex. Here the cells performing the same function are arranged into tissues. In animals like Annelids, Arthropods, Molluscs, Echinoderms and Chordates, organs have associated to form functional systems. Each system is concerned with a specific physiological function.

This pattern is known as organ system level of organization. The digestive system in platyhelminthes has only a single opening to the outside of the body that serves as both mouth and anus, therefore, it is incomplete. A complete digestive system has two openings, mouth and anus.

Similarly, the circulatory system may be of two types: one is Open type where the blood is pumped out of the heart; and the cells and tissues are directly bathed in it. Other is closed type, where the blood is circulated through a series of vessels of varying diameters.

Taxonomy, in a broad sense is the science of classification, but more strictly the classification of living and extinct organisms—i.e., biological classification. The term is derived from the Greek taxis (“arrangement”) and nomos (“law”). Taxonomy is, therefore, the methodology and principles of systematic botany and zoology and sets up arrangements of the kinds of plants and animals in hierarchies of superior and subordinate groups. Among biologists the Linnaean system of binomial nomenclature, created by Swedish naturalist Carolus Linnaeus in the 1750s, is internationally accepted.

 

Animal Taxonomy

Animals and other organisms are classified within a succession of nested groups that ranges from the general to the particular.

Popularly, classifications of living organisms arise according to need and are often superficial. Anglo-Saxon terms such as worm and fish have been used to refer, respectively, to any creeping thing—snake, earthworm, intestinal parasite, or dragon—and to any swimming or aquatic thing. Although the term fish is common to the names shellfish, crayfish, and starfish, there are more anatomical differences between a shellfish and a starfish than there are between a bony fish and a man. Vernacular names vary widely. The American robin (Turdus migratorius), for example, is not the English robin (Erithacus rubecula), and the mountain ash (Sorbus) has only a superficial resemblance to a true ash.

Biologists, however, have attempted to view all living organisms with equal thoroughness and thus have devised a formal classification. A formal classification provides the basis for a relatively uniform and internationally understood nomenclature, thereby simplifying cross-referencing and retrieval of information. The usage of the terms taxonomy and systematics with regard to biological classification varies greatly. American evolutionist Ernst  Mayer  has stated that “taxonomy is the theory and practice of classifying organisms” and “systematics is the science of the diversity of organisms”; the latter in such a sense, therefore, has a considerable interrelations with evolution, ecology, genetics, behavior, and comparative physiology that taxonomy need not have.

Classification of insects

There are over 24,000 species of insects in Britain and, globally, well over one million species have been described to date. The classification of insects can be complex but it is very important to group and identify insects so that they can be studied reliably. Insects, like all animals, are classified using a hierarchical system of classification. Here is an example using the marmalade hoverfly, Episyrphus balteatus:

Kingdom: Animalia (all animals)

Phylum: Arthropoda (all arthropods)

Class: Insecta (only the insects)

Order: Diptera (only the true flies)

Family: Syrphidae (only the hoverflies)

Genus: Episyrphus (only a sub-set of the hoverflies)

Species: balteatus

From this hierarchy we derive the scientific name for the marmalade hoverfly – Episyrphus balteatus. This ‘binomial nomenclature’ allows there to be a two-word, universally recognised name for each species, which avoids the confusion that might arise from using a common name in one particular language or from a particular region. Traditionally, the genus and species should be written in italics.

There are also groupings that fit between the traditional ranks of the hierarchy which are often included because they are evolutionarily important. For example, insects in the wider sense constitute the subphylum Hexapoda, which separates the arthropods with six legs from others such as centipedes and spiders. Hexapoda is then divided into two classes: the Entognatha includes primitively wingless hexapods such as springtails, while all the ‘true’ insects are subdivided into five major groups also known as superorders, the Apterygota, Palaeoptera, Polyneoptera, Paraneoptera and Endopterygota.

 

 

 

 

 

 

 

 

 

 

 

 

CAPTER 2

TEACHING FLOWERING PLANTS

Flowers are the reproductive part of a plant. They are not only involved in reproduction, but are also a source of food for other living organisms. They are a rich source of nectar.

Flowers can either be

· Complete

· Incomplete.

A complete flower is the one that consists of sepals, petals, stamens and pistil. On the contrary, an incomplete flower is the one that lacks one or more of these structures.

A complete flower consists of two different parts:

· Vegetative Part

· Reproductive Part

Let us have a detailed look at the different parts of a flower.

 

 

 

Parts of a Flower

Parts of a Flower

The different parts of a flower are mentioned below:

Vegetative Parts of a Flower

The vegetative part of a flower consists of the following:

· Petals: This is a bright-coloured part that attracts bees, insects, and birds. Colour of petals varies from plant to plant; some are bright while some are pale coloured. Thus, petals help us to differentiate one flower from another.

· Sepals: Sepal is the green-coloured part beneath the petals to protect rising buds. Some flowers have fused petals-sepals while a few have separated petals-sepals.

Reproductive Parts of a Flower

Flowers contain the plant’s reproductive structures

In different plants, the number of petals, sepals, stamens and pistils can vary. The presence of these parts differentiates the flower into complete or incomplete. Apart from these parts, a flower includes reproductive parts – stamen and pistil.  A flower may have only female parts, only male parts, or both.

The reproductive parts of a flower consist of the following:

· Stamen: This is the male reproductive organ and is also known as Androecium. It consists of two parts namely: anther and filaments.

1. The anther is a yellowish, sac-like structure, involved in producing and storing the pollens.

2. The filament is a slender, threadlike object, which functions by supporting the anther.

· Pistil: This is the innermost part and the female reproductive organ of a flower which comprises three parts -stigma, style and ovary. This is collectively known as the pistil.

1. Stigma: It is the topmost part or receptive tip of carpels in the gynoecium of a flower.

2. Style: It is the long tube-like slender stalk that connects stigma and the ovary.

3. Ovary: It is the ductless reproductive gland that holds a lot of ovules. It is the part of the plant where the seed formation takes place.

Whorls

Along with the vegetative and reproductive parts, a flower is also composed of four whorls, which are largely responsible for the radial arrangement of a flower. A typical flower has a circular section with a common centre, which can be clearly observed and distinguished from the top of the flower. There are four whorls:

Calyx

The calyx is the outermost whorl of a flower. It comprises sepals, tiny leaves present at the base of a flower. These protect the flower whorls against mechanical injuries and desiccation. Some plants have coloured sepals the calyx and are called petaloid.

If the sepals are free the calyx is called polysepalous, and if they are united it is called gamosepalous.

In many flowers, the sepals fall off before the flower even opens fully. Such sepals are known as caducous.

In some, the sepals fall off after fertilization. Such sepals are known as deciduous.

The persistent sepals remain up to the fruiting stage.

Corolla

This is the second whorl of a flower. It contains petals which serve two main functions:

· To attract pollinators.

· To protect the reproductive parts of a flower

Petals are brightly coloured and scented to attract animals and insects for pollination. The calyx and corolla are collectively called the perianth.

Different forms of the corolla are found in the flowers.

· Polypetalous Regular

· Polypetalous Irregular

· Gamopetalous Regular

· Gamopetalous Irregular

 

 

Stamens 

Stamen is also known as the third whorl of the flower and is the male reproductive part. It consists of a filament which is a thread-like structure with a circular structure anther on the top. Pollen is produced by the anther which contributes to the male reproductive process of the plant. All the stamens do not bear fertile anthers.

Carpels The carpel is the fourth whorl of the flower present in the centre. The carpels contain the pistil, the female reproductive part of the flower. It comprises the ovary, style, and stigma. The egg or the ovule is present in the ovary. After fertilization, sometimes the ovary turns into the fruit to keep the seed. At the top of the ovary is a vertical structure called style that supports the stigma. The dispersed pollens stick to the stigma and travel down to the ovary through the style.

This was an overview of the different parts of a flower

 

Functions of a flower    

The primary purpose of a flower is reproduction. Since the flowers are the reproductive organs of plant, the male parts of a flower consist of one or more stamens. Each stamen is made up of paired anthers (sacs containing pollen) on a filament or stalk.

Female reproductive part of a flower that forms pistil. A pistil may contain a single carpel or multiple carpels fused together.

It aids in fertilization

In plants, fertilization is a process of sexual reproduction, which occurs after pollination and germination.

Fertilization can be defined as the fusion of the male gametes (pollen) with the female gametes (ovum) to form a diploid zygote. It is a physiochemical process which occurs after the pollination of the carpel. The complete series of this process takes place in the zygote to develop into a seed.

 

 

 

 

 

In the fertilization process, flowers play a significant role as they are the reproductive structures of angiosperms (flowering plants). The method of fertilization in plants occurs when gametes in haploid conditions fuse to produce a diploid zygote.
In the course of fertilization, male gametes get transferred into the female reproductive organs through pollinators (honey bees, birds, bats, butterflies, flower beetles) and the final product will be the formation of the embryo in a seed.

v It brings about pollination:

Pollination is the transfer of pollen grains from the anther of a flower to the stigma of a flower of the same species. There are two main types of pollination namely cross pollination and self-pollination.

Self-pollination: This refers to the transfer of pollen from the anther to the stigma of the same flower, or another flower of the same plant. Self-pollination happens in flowers where the stamen and carpels mature at the same time and are positioned so that the pollen can land on the flower’s stamen. This pollination does not require an investment from the plant to provide nectar and pollen as food for pollinators.

      

 

Cross pollination: It is the transfer of pollen from the anther of one flower to the stigma of another flower on a different individual of the same species.

v  Medicinal aid:

Many flowers have medicinal uses, such as begonia for eliminating toxins in the body, and calendula, sunflower and honeysuckle for treating sore throats and tonsillitis. Cornflower can be used to treat acne, while valerian and California poppy relieve menstrual cramps. Cats even use flowers to cause vomiting and thus eliminate stomach distress.

v It produces fruits and seeds to enhance dispersal:

A fruit is formed as a result of pollination and fertilization. A fruit is described as a matured ovary containing seeds.

Seed is a fertilized ovum consisting of an embryo, food store and a protective Testa. Without flowers there wouldn’t be new species to continue the generational trend.

v It serves as food for some animals and humans:

It serves as a source of food with the actual flower being edible in some instances. Insects like butterfly, grasshopper, and even bees use the nectar of flower in the production of honey and birds also feed on the nectar.

Flower that serves as food is very essential for health and the production of essential nutrients. Examples flower like squash blossoms provide the body with vitamin A, B and C.

 

PHOTOSYNTHESIS

Chloroplast contain a given substance called chlorophyll. Thus absorbs the photosynthesis is the process used by plants and other organisms to convert light energy into chemical energy. Photosynthesis takes place inside plants cells in small objects called chloroplast. Plants get carbon dioxide from the air through their leaves. Light energy comes from sun.

The oxygen produced Is released into the air from the leaves. The glucose produced can be turned into other substances, such as starch and plant oils, which are used as an energy store. This can be released by respiration.

6C02+6H2Osunlight/chlorophyll C6H12O6+6O2

At the end of the process, glucose is produced which is stored in the form of starch i.e. the end product and oxygen is released as the by-product.

 

FACTORS THAT AFFECT PHOTOSYNTHESIS

There are also some factors that can affect photosynthesis, temperature, light intensity and carbon dioxide, concentration.

Light Intensity

Light intensity, without Light cannot photosynthesis very quickly even if there is plenty of water and carbon dioxide. Increasing the light intensity will boost the rate of photosynthesis.

Temperature

Temperature, if it gets cold, the rate of photosynthesis will decrease. plants cannot photosynthesize if it gets too hot.

Carbon Dioxide

Carbon dioxide concentration, even if there is plenty of light, a plant cannot photosynthesize if there is insufficient carbon dioxide.

 

Importance of Photosynthesis

1. Photosynthesis helps plants to manufacture their own food

2. It produces oxygen for human survival which helps in reducing carbon dioxide in the atmosphere

3. It also enhances plant growth

 

 

 

 

 

 

 

 

 

 

CHAPTER 3

TEACHING FRUIT FORMATION AND DISPERSAL

 Fruit and Seed

The seeds and fruits are the results of fertilization or sexual reproduction in plants. The ovary in angiosperms develop into the fruit whereas the ovules become the seeds enclosed within the fruit.

Seeds contained within the fruits need to be dispersed far from the mother plant so they may find favorable and less competitive conditions in which they can germinate or grow.

Dispersal of Fruit and Seed

Fruit and seed dispersal is the mechanism by which fruits and seeds are transported to new sites for germination and the establishment of new individuals.   

Fruit and seed dispersal is the process whereby fruits and seeds are scattered from their origin.

Some fruits have build-in mechanism so they can disperse by themselves, whereas other require the help of agents like wind, water, animals etc.

Agents of Fruit and Seed

Agents of fruit and seed dispersal are simply referred to as the various ways through which fruits and seeds are dispersed from their parent plant. Example wind, water, animals, explosive mechanism.

Wind Dispersal

Wind dispersed fruits are lightweight and may have win g-like appendages that allow them to be carried by the wind. Some have parachute like structure to help keep them afloat. Some fruits for examples the dandelion, it has hairy, weightless structure that are suited to dispersed by wind. Other examples are cotton, seeds of pepper and tomatoes etc.

Water Dispersal

Seed dispersed by water are contained in the light and buoyant fruits giving them the ability to float thus their relative density is lower than water. Coconuts are well known for their ability to float on water to reach land where they can germinate. Similarly, willow and silver birches produce lightweight fruit that can float on water.

 

Animal Dispersal

Animals eat fleshy fruits like tomatoes seed that are not digested are excreted in their droppings. Some animals, such as squirrel, bury seed containing fruit for later use. If the squirrel does not find its stash of fruits and if conditions are favorable the seed germinate. Some fruits have hooks or sticky structures the stick to an animal coat and are then transported to another place. Also fruits dispersed by animals are colorful and scented to attract these animals.

Explosion Mechanism

Some plants distribute their seeds by violently ejecting them so that that they fall well away from the parent plant. This is explosive dispersal. An example of this is plants which belong to the pear family (leguminosae), they produce seed pods which dries in the sun.

As a pod dries, tension is set up in the wall of the pod eventually causing it to split along two lines of weakness. As the two halves curl back, suddenly released line a tense spring, they flick out the seed inside in an explosive manner. Gorse is a good example of this sitting near Gorse bushes on a hot day in summer in Britain can be like sitting near a firing range, as the exploding pods sound almost like gun shot. The small seeds are very effective thrown away from the immediate area.

 

Advantages of fruit and seed dispersal.

1) It encourages afforestation because plants grow in new places.

2) It prevents overcrowding of plants.

3) It reduces competition of sunlight, water and other soil minerals among plants.

4) It reduces the spread of epidemic diseases among crowded plant species.

 

 

 

 

 

 

CHAPTER 4

CARBON AND NITROGEN CYCLE

Carbon Cycle

Carbon cycle is the process where carbon compounds are interchanged among the biosphere, geosphere, pedosphere, hydrosphere and atmosphere of the earth.

The following are steps involved in the process of the carbon cycle;

1. Carbon present in the atmosphere in the form of CO₂ is absorbed by plants for photosynthesis.

2. The plants are then consumed by animals and carbon gets bioaccumulated into their bodies.

3. These animals and plants eventually die, decompose and carbon is released back into the atmosphere.

4. Some of the carbon that is not released back into the atmosphere eventually become fossil fuels.

5. These fossil fuels are then used for man-made activities which pump more carbon back into the atmosphere.

Carbon Cycle Diagram

The carbon cycle diagram below elaborates the flow of carbon along different paths.

 

Carbon Cycle diagram showing the flow of carbon, its sources and paths.

Carbon Cycle on Land

Carbon in the atmosphere is present in the form of carbon dioxide. Carbon enters the atmosphere through natural processes such as respiration and industrial applications such as burning fossil fuels. The process of photosynthesis involves the absorption of CO₂ by plants to produce carbohydrates. The equation is as follows:

CO₂ + H₂O + energy → (CH₂O)n +O₂

Carbon compounds are passed along the food chain from the producers to consumers. The majority of the carbon exists in the body in the form of carbon dioxide through respiration. The role of decomposers is to eat the dead organism and return the carbon from their body back into the atmosphere. The equation for this process is:

(CH₂O)n +O₂ → CO₂ + H₂O

Oceanic Carbon Cycle

This is essentially a carbon cycle but in the sea. Ecologically, oceans take in more carbon than it gives out. Hence, it is called a “carbon sink.” Marine animals convert carbon to calcium carbonate and this forms the raw building materials require to create hard shells, similar to the ones found in clams and oysters.

When organisms with calcium carbonate shells die, their body decomposes, leaving behind their hard shells. These accumulate on the seafloor and are eventually broken down by the waves and compacted under enormous pressure, forming limestone.

When these limestone rocks are exposed to air, they get weathered and the carbon is released back into the atmosphere as carbon dioxide.

Importance of Carbon Cycle

Even though carbon dioxide is found in small traces in the atmosphere, it plays a vital role in balancing the energy and traps the long-wave radiations from the sun. Therefore, it acts like a blanket over the planet. If the carbon cycle is disturbed it will result in serious consequences such as climatic changes and global warming.

Carbon is an integral component of every life form on earth. From proteins and lipids to even our DNA. Furthermore, all known life on earth is based on carbon. Hence, the carbon cycle, along with the nitrogen cycle and oxygen cycle, plays a vital role in the existence of life on earth.

Key Points on Carbon Cycle

· Carbon cycle explains the movement of carbon between the earth’s biosphere, geosphere, hydrosphere and atmosphere.

· Carbon is an important element of life.

· Carbon dioxide in the atmosphere is taken up by the green plants and other photosynthetic organisms and is converted into organic molecules that travel through the food chain. Carbon atoms are then released as carbon dioxide when organisms respire.

· The formation of fossil fuels and sedimentary rocks contribute to the carbon cycle for very long periods.

· The carbon cycle is associated with the availability of other compounds as well.

 

 

What is the carbon cycle? Explain.

Cycle is a biogeochemical cycle where various carbon compounds are interchanged among the various layers of the earth, namely, the biosphere, geosphere, pedosphere, hydrosphere and atmosphere.

What are the 4 steps of the carbon cycle?

· Carbon enters the atmosphere as CO2

· CO2 is absorbed by autotrophs such as green plants

· Animals consume plants, thereby, incorporating carbon into their system

· Animals and plants die, their bodies decompose and carbon is reabsorbed back into the atmosphere.

What are the types of the carbon cycle?

Carbon Cycle can be classified into two types based on the duration of the process into two types:

· Short term – This type occurs within a relatively short period of time. It is named as such because it takes just days, months or years for carbon to flow across the various carbon reservoirs.

· Long term – This type takes thousands of years to occur. The excess carbon from the short-term cycle is stored for a long time before they are released.

Why is the carbon cycle important?

Carbon Cycle is an important aspect of the survival of all life on earth. From an environmental perspective, carbon provides insulation by trapping the sun’s heat. From a biological perspective, carbon is the building block of life and forms stable bonds with other elements necessary for life.

 

Nitrogen Cycle

Nitrogen cycle is a biogeochemical process which transforms the inert nitrogen present in the atmosphere to a more usable form for living organisms.

Nitrogen is a key nutrient element in the atmosphere making up 78% of the atmosphere. However, the abundant nitrogen in the atmosphere cannot be directly used by plants or animals. It must undergo various stages before it can be used by living organisms. These stages are as follows;

a. Nitrogen fixation

It is the initial step of the nitrogen cycle. Here, atmospheric nitrogen (N2) which is available in the form of gas is converted into the usable form ammonia (NH3). During the process, the inert form of nitrogen is deposited into the soil from the atmosphere and surface waters, mainly through precipitation. Later, the nitrogen undergoes a set of changes in which two nitrogen atoms get separated and combine with hydrogen to form ammonia (NH3). The process is completed by a symbiotic bacteria called Diazotrophs. Azobacter and Rhizobium also play a major role in this process.

b. Nitrification

In this process, the ammonia is converted into nitrate by the presence of bacteria in the soil. Nitrites are formed by the oxidation of ammonia with the help of Nitrosomonas bacteria. Later, the produced nitrites are converted into nitrate by Nitrobacter. The conversion is very important because, ammonium gas is toxic for plants. The reaction involved is as follows;

2NH₄⁺ +3O₂   2NO₂^- + 4H⁺ + H₂O

2NO₂^- + O₂  2NO₃^- 

 

 

c. Assimilation

Plants take in the nitrogen compound from the soil with the help of their roots which are   available in the form of ammonia, nitrite ions, or ammonium ions and are and are used in the formation of the plant and animal proteins. In this way, it enters the food web when the primary consumers eat the plant.

d. Ammonification

When plants or animals die, the nitrogen present in the organic matter is released back into the soil. The decomposers (bacteria or fungi) present in the soil convert the organic matter back into ammonium. This process produces ammonia which is used for other biological processes.

e. Denitrification

This is a process in which nitrogen compounds make its way back into the atmosphere by converting nitrate (NO₃^-) into gaseous nitrogen (N₂). This is the final stage and occurs in the absence of oxygen. Denitrification is carried out by denitrifying bacteria (Clostridium and Pseudomonas) which process nitrate to gain oxygen and give out free nitrogen gas as a by-product.

 

 

 

Nitrogen Cycle diagram showing the flow of nitrogen, its sources and paths

 

GREENHOUSE EFFECT

Greenhouse effect is the process by which radiation from a planet’s atmosphere warms the planet’s surface to a temperature above what it would be without the atmosphere. Examples of greenhouse gases that cause greenhouse effect are;

i. Methane

ii. Ozone

iii. Water vapour and

iv. Carbon dioxide.

Like glass in a greenhouse, these gases admit incoming solar radiations but retard its radiation back into the space. The intensity of the down radiation depends on the atmosphere’s temperature and the amount of greenhouse gases that the atmosphere contains.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CHAPTER 5

FARMING SYSTEMS

A farming system is defined as a population of individual farm systems that have broadly similar resource base, enterprise patterns, household livelihoods and constraints, and for which similar development agriculture. Farmers aim at providing enough, healthy food to feed the ever-increasing population worldwide. Different types of farming practices practiced in different regions across the world based on various factors (climate and soil fertility) that affect the type of farming strategies and interventions would be appropriate. Farming involves rearing of animals and crop cultivation; it is an important part of practices a farmer can adopt.

Types Of Farming System

There are numerous farming systems across the world at large. These are;

Arable Farming

Arable farming; this involves growing of crops in warm climate. It is practiced on gently sloping or flat land with deep, fertile soil. It is important that the land is neither too wet nor dry. Land ideal for growing crops should be fairly sheltered and suitable for use of machinery. In the UK, this type of farming is mainly adopted in the East and South.

 

Advantages of Arable Farming

1. A larger portion of land can be ploughed within a shorter time

2. Soil is enriched with oxygen

3. There is increase in productivity

4. There is reduction of labor cost and human efforts

 

Disadvantages Of Arable Farming

1. Ploughing in a site overgrown with weeds can only worsen the situation, since seeds of weeds and pest can get spread in the process.

2. It leads to subsequent depletion of the soils if the fertile layer(humus) is not restored properly

3. This can reduce the strength of the soil to support plants  

       

Pastoral Farming

Pastoral farming; this is the practice of rearing animals only in cold and wet climates not ideal for growing crops. It is also known in some regions as livestock farming or grazing. Land with steep slopes and poor soils cannot support the use of machinery nor provide the nutrients crops need to grow. Only heather and grasses can grow on that kind of land. There are two main types of pastoral farming, namely; intensive pastoral farming and extensive pastoral farming

 

 

Intensive pastoral farming; intensive farms generally take up a fairly small area of land, but aim to have a very high output, through massive input of capital and labour. These farms use machines and new technologies to become as efficient and cost-effective as possible.

Extensive pastoral farming; it is the direct opposite of intensive farming. The farms are large in comparison to the money injected into them or the labour used.

 

Advantages of Pastoral Farming

1. The farmer can use the dropping of the animals to fertilize the grassland on which the animals feed.

2. The farmer can obtain milk or meat from the animals.

3. The frequent movement of the animals makes the animals exercise their bodies.

 

Disadvantages of Pastoral Farming

1. Soil erosion is likely to occur on the grassland due to overgrazing.

2. Animals are prone to tsetsefly attack when they are move to tsetsefly-infected area.

 

Crop Rotation

Crop Rotation; this is a system of farming where different types of crops are grown on the same piece of land in a definite order or cycle or sequence or from season to season.

 

Advantages of Crop Rotation

1. Nutrients in the soil are efficiently used by crops since with different root systems are made to follow each other.

2. Soil fertility is maintained because of the inclusion of leguminous plants.

3. Cycles of pest are disrupted or pests are controlled.

4. Crop rotation controls soil erosion.

5. Crop production is possible on a piece of land for a longer period (that is, it provides economic land use.)

 

Disadvantages of Crop Rotation

1. It involves risk.

2. Improper implementation can cause much more harm than good.

3. Obligatory crop diversification.

4. Requires more knowledge and skills.

 

Benefits of including legume in crop rotation

1. They increase the fertility of soil.

2. They improve nitrogen status of the soil.

3. They break pest and disease cycle.

4. They control soil erosion when use as cover crops.

 

Land Rotation

Land Rotation; this is a farming system in which a farmer cultivates a piece of land for sometimes and then leaves it to cultivate a new land when the fertility of the old land is lost without moving his family and settlement.

Advantages of land rotation

1. Disease build up is reduced and also pest attack is reduced.

2. The use of simple farm tools makes land rotation a cheaper method of farming.

3. The land regains it fertility after a fallow period.

 

Disadvantages of land rotation

1. The virgin forest is destroyed.

2. Land rotation cannot be practiced where land is scarce.

3. The farmer does not derive full benefit from the investment made in clearing his land.

4. Constant clearing of new lands for farming involves a lot of work and is expensive.

 

Differences between land rotation and crop rotation

1. In crop rotation, the farmer maintains one piece of land while in land rotation, the farmer works on different pieces of land.

2. In crop rotation, different crops are grown in a definite order while in land rotation crops are not grown in any order.

3. Crop rotation requires inclusion of a legume while in land rotation, legumes are not necessary.

Mixed Farming

Mixed Farming; this is a system of farming in which crops and animals are raised or produced by the same farmer on the same piece of land at the same time. A large area of land is used for mixed farming.

Advantages of mixed farming

1. Animals feed on crop residues or by-product. For example, bran, husks and straw are used as animal feed.

2. Maintenance or improvement of soil fertility is achieved by the use of farm yard manual or animal droppings.

3. There is regular supply of food for the farmer and his family.

4. There is efficient use of labour throughout the year.

5. Some animals may provide power on the farm for ploughing, harrowing, planting, caring or transportation

 

Disadvantages of mixed farming

1. The farmer works throughout the whole year.

2. He needs knowledge of both crops and animals.

3. He requires a lot of skills to be able to manage the crops and animals effectively.

4. When the animals are not well confined, the crops can be destroyed.

 

Mixed Cropping

Mixed cropping; this is a farming method in which the farmer grows two or more types of crops on the same piece of land at the same time.

Advantages Of Mixed Cropping

1. The farmer obtains most of his crop product from his farm.

2. The dense cover of the leaves of crops, protect the soil surface from being eroded.

3. The farmer obtains food for a longer period of time, because he harvests the crops at different times.

4. The spread of diseases is checked.

5. Nutrients in the soil are fully utilized.

Disadvantages of mixed cropping

1. Improper spacing may lead to shading of crops.

2. There is likely competition for water, space, nutrients and light among the various crops.

3. Nutrients and water in the soil may be used up faster.

4. Mechanization of the farm is impossible.

 

Differences Between Mixed Farming And Mixed Cropping

1. In mixed farming, crops are grown and animals are reared while in mixed cropping, only crops of different types are grown.

2. In mixed farming, the farmer obtains both animal and plants products from his farm while in mixed cropping, the farmer only obtains plant products from his farm.

3. In mixed farming, plants and animal waste are available to serve as manure while in mixed cropping, only plants waste is available to serve as manure.

 

Organic Farming

Organic farming; this is a type of farming system in which natural processes are used to produced food and to maintain soil fertility and control pests and weeds.

 

Advantages of organic farming

1. Organic farming produces food with high nutrients content which is free of chemicals.

2. It enhances soil structure.

3. It conserves water.

4. It produces food that can be stored for a longer time.

5. Organically grown crops are able to compete with weeds present.

 

Disadvantages Of Organic Farming

1. Organic farming is labour intensive.

2. It requires more skills.

3. It cannot be used to produce food on a large scale.

 

 

 

Distinguishing between organic farming and crop rotation

Organic farming requires careful planning in maintaining soil fertility and controlling disease and pests without the use of agrochemicals while in crop rotation, natural processes are used to maintain soil fertility. However, agrochemicals like pesticides are used to control pests and diseases.

 

Shifting Cultivation

Shifting cultivation; this is a farming system where the farmer clears and uses a land for a number of years and then leaves to settle on another plot until the previous land fallows or regains its fertility.

Advantages Of Shifting Cultivation

1. The land becomes fertile again during the fallow period with the use of fertilizer or no fertilizer.

2. It reduces disease build-up in the farm.

3. Important soil organisms are not killed.

4. It is a relatively cheaper method of farming.

 

Disadvantages Of Shifting Cultivation

1. It destroys the virgin forest.

2. cannot be practiced in places where land is scarce.

3. The practice is expensive because of the constant clearing of new land.

4. It involves a lot of work as a result of periodic movement of settlement.

5. It is a hindrance to commercial farming.

Mono Cropping

Mono cropping; this is a farming system in which the farmer cultivates one type of annual crop, on a piece of land, at a time and changes it after harvested.

   

Advantages Of Mono Cropping

1. Control pests and diseases can be done easily.

2. It enables demand for a particular crop to be met.

3. Managerial skill for the crop is developed.

4. Soil nutrients are effectively used or there is maximum use of soil nutrients.

 

Disadvantages Of Mono Cropping

1. Farmers are exposed to the danger of a poor harvest as a result of diverse climatic conditions.

2. Invasion of pests and diseases is enhanced.

3. Fall in market price may lead to serious loss of profit or capital.

 

Mono Culture

Mono culture; is a farming system in which a farmer grows one type of annual crop or perennial crop on the same piece of land from year to year. It is usually practiced when a particular crop is in high demand or has a good price.

 

Advantages Of Mono Culture

1. Farm mechanization is easy.

2. The farmer specializes the cultivation of his crops.

3. The farmer can easily produce his crop a large scale.

4. Cultural practices are easier to carry out.

 

Disadvantages Of Mono Culture

1. Diseases spread easily.

2. Pests easily attack crops.

3. Soil fertility is lost since the same types of nutrients are removed from the soil year after year.

 

Differences Between Mono Culture And Mono Cropping

In mono culture, the famer continues to grow the same type of crop year after year but in mono cropping, the farmer changes the crops he grows after harvest.

 

Ecological Farming

Ecological farming; is a method of farming in which the vegetation or environment is protected. Chemicals and machinery are not used in ecological farming.

Advantages Of Ecological Farming

1. Soil erosion is checked by the vegetative cover.

2. Environmental pollution is reduced.

3. Desertification is avoided.

4. The incidence of pests is greatly reduced.

 

Disadvantage of ecological farming

Location relative to the consumer, can reduced the food miles’ factor to help minimize damage to the biosphere by combustion.

 

Importance of Farming System In Agriculture

1. Sources of livelihood.

2. Contribution to national revenue.

3. Supply of food as well as fodder.

4. Marketable surplus.

5. Sources of raw material.

6. Foreign exchange resources.

7. Sources of saving

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CHAPTER 6

TEACHING ABOUT THE RESPIRATORY SYSTEM

The respiratory system is the network of organs and tissues that help you breathe. It includes your airways, lungs, and blood vessels. The muscles that power your lungs are also part of the respiratory system. These parts work together to move oxygen throughout the body and clean out waste gases like carbon dioxide.

Functions

1. Allows you to talk and to smell.

2. Brings air to body temperature and moisturizes it to the humidity level your body needs.

3. Delivers oxygen to the cells in your body.

4. Removes waste gases, including carbon dioxide, from the body when you exhale.

5. Protects your airways from harmful substances and irritants.

The parts of the respiratory system

The respiratory system has many different parts that work together to help you breathe. Each group of parts has many separate components.

Your airways deliver air to your lungs. Your airways are a complicated system that includes your:

1. Mouth and nose: Openings that pull air from outside your body into your respiratory system.

2. Sinuses: Hollow areas between the bones in your head that help regulate the temperature and humidity of the air you inhale.

3. Pharynx (throat): Tube that delivers air from your mouth and nose to the trachea (windpipe).

4. Trachea: Passage connecting your throat and lungs.

5. Bronchial tubes: Tubes at the bottom of your windpipe that connect into each lung.

6. Lungs: Two organs that remove oxygen from the air and pass it into your blood.

From your lungs, your bloodstream delivers oxygen to all your organs and other tissues.

Muscles and bones help move the air you inhale into and out of your lungs. Some of the bones and muscles in the respiratory system include your:

· Diaphragm: Muscle that helps your lungs pull in air and push it out

· Ribs: Bones that surround and protect your lungs and heart

When you breathe out, your blood carries carbon dioxide and other waste out of the body. Other components that work with the lungs and blood vessels include:

· Alveoli: Tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide takes place.

· Bronchioles: Small branches of the bronchial tubes that lead to the alveoli.

· Capillaries: Blood vessels in the alveoli walls that move oxygen and carbon dioxide.

· Lung lobes: Sections of the lungs – three lobes in the right lung and two in the left lung.

· Pleura: Thin sacs that surround each lung lobe and separate your lungs from the chest wall.

Some of the other components of your respiratory system include:

· Cilia: Tiny hairs that move in a wave-like motion to filter dust and other irritants out of your airways.

· Epiglottis: Tissue flap at the entrance to the trachea that closes when you swallow to keep food and liquids out of your airway.

· Larynx (voice box): Hollow organ that allows you to talk and make sounds when air moves in and out.

     

Structure of the respiratory system

 

The Conditions that can Affect the Respiratory System

Many conditions can affect the organs and tissues that make up the respiratory system. Some develop due to irritants you breathe in from the air, including viruses or bacteria that cause infection. Others occur as a result of disease or getting older.

Conditions that can cause inflammation (swelling, irritation, and pain) or otherwise affect the respiratory system include:

1. Allergies: Inhaling proteins, such as dust, mold, and pollen, can cause respiratory allergies in some people. These proteins can cause inflammation in your airways.

2. Asthma: A chronic (long-term) disorder, asthma causes inflammation in the airways that can make breathing difficult.

3. Infection: Infections can lead to pneumonia (inflammation of the lungs) or bronchitis (inflammation of the bronchial tubes). Common respiratory infections include the flu (influenza) or a cold.

4. Disease: Respiratory disorders include lung cancer and chronic obstructive pulmonary disease (COPD). These illnesses can harm the respiratory system’s ability to deliver oxygen throughout the body and filter out waste gases.

5. Aging: Lung capacity decreases as you get older.

6. Damage: Damage to the respiratory system can cause breathing problems.

 

How To Keep The Respiratory System Healthy

Being able to clear mucus out of the lungs and airways is important for respiratory health.

To keep your respiratory system healthy, you should:

1. Avoid pollutants that can damage your airways, including secondhand smoke, chemicals, and radon (a radioactive gas that can cause cancer). Wear a mask if you are exposed to fumes, dust or other types of pollutants for any reason.

2. Avoid smoking yourself

3. Eat a healthy diet with lots of fruits and vegetables and drink water to stay hydrated

4. Exercise regularly to keep your lungs healthy.

5. Prevent infections by washing your hands often and getting a flu vaccine each year.

 

DEFINITIONS OF GASEOUS EXCHANGE

Gas exchange is the process of absorbing inhaled atmospheric oxygen molecules into the bloodstream and offloading carbon dioxide from the bloodstream into the atmosphere.

Gas exchange is the process by which oxygen is transferred from the atmosphere to bodily tissues for use in metabolism ; and the gas produced by metabolism, carbon dioxide, is transferred from tissues to the atmosphere.

This process is completed in the lungs through the diffusion of gases from areas of high concentration to areas of low concentration. The process also requires that oxygen move from its gaseous environment into a liquid environment and carbon dioxide move from a liquid environment into a gaseous environment.

 

PROCESSES IN GASEOUS EXCHANGE

Three processes are essential for the transfer of oxygen from the outside air to the blood flowing through the lungs: ventilation, diffusion, and perfusion.

· Ventilation is the process by which air moves in and out of the lungs.

· Diffusion is the spontaneous movement of gases, without the use of any energy or effort by the body, between the gas in the alveoli and the blood in the capillaries in the lungs.

· Perfusion is the process by which the cardiovascular system pumps blood throughout the lungs.

Air enters the body through the mouth or nose and quickly moves to the pharynx, or throat. From there, it passes through the larynx, or voice box, and enters the trachea.

The trachea is a strong tube that contains rings of cartilage that prevent it from collapsing.

Within the lungs, the trachea branches into a left and right bronchus. These further divide into smaller and smaller branches called bronchioles.

The smallest bronchioles end in tiny air sacs. These are called alveoli. They inflate when a person inhales and deflate when a person exhales.

During gas exchange oxygen moves from the lungs to the bloodstream. At the same time carbon dioxide passes from the blood to the lungs. This happens in the lungs between the alveoli and a network of tiny blood vessels called capillaries, which are located in the walls of the alveoli.

Here you see red blood cells traveling through the capillaries. The walls of the alveoli share a membrane with the capillaries. That's how close they are.

This lets oxygen and carbon dioxide diffuse, or move freely, between the respiratory system and the bloodstream.

Oxygen molecules attach to red blood cells, which travel back to the heart. At the same time, the carbon dioxide molecules in the alveoli are blown out of the body the next time a person exhales.

The organ system responsible for gas exchange is the Respiratory system.

 

FACTORS AFFECTING GAS EXCHANGE

The main factors that affect gas exchange in both animals and plants:

· SURFACE AREA OF THE MEMBRANE: The larger the surface area of the membrane the higher the rate of gas exchange that takes place. There is a directly proportional relationship between surface area and gas exchange because when the surface area is large more blood and air are able to circulate hence increasing the rate of gas exchange.

· CONCENTRATION GRADIENT: Concentration gradient is only possible when a membrane separates two surface areas with different concentration of gases. The difference is what actually facilitates the process of gas exchange because the gases are able to move from areas of high concentration to those of lower concentration.

· THICKNESS OF THE MEMBRANE: The rate of gaseous exchange process is also affected by the thickness of the membrane through which the gases have to diffuse. A thicker membrane reduces the rate at which gases diffuse from areas of higher concentration to those of lower concentration. This is an inversely proportional relationship and hence reduced thickness of a membrane can increase the speed at which gases flow.

· THE DISTANCE OF DIFFUSION:.The distance across which air and blood or plasma fluids have to travel to diffuse also determines the rate of gaseous exchange. In singular celled organisms gaseous exchange tends to be faster because the gases only have to diffuse through one cell membrane while in complex creatures gas exchange requires complex transportation and respiratory system because the gases are transported through a longer distance. This takes a longer period of time.

 

OTHER FACTORS AFFECTING GAS EXCHANGE

The exchange of gas, or respiration, occurs between 17,280 - 28,800 times a day. Although it's a simple process, several factors such as exercise, smoking, and asthma can affect how this gas exchange happens.

Exercise

We keep hearing that exercise is good for the body. This is very true when it comes to gas exchange. You may or may not think you're exercising, but playing football, volleyball, or any other sport is exercise for the body. Your body will need more oxygen coming into the body in order to keep the body moving during exercise. You probably notice that you breathe faster and deeper as you exercise. This is your body's way of increasing the amount of oxygen coming in. When you breathe deeper, then the amount of oxygen filling your lungs, known as lung volume, will increase. Your respiration rate, which is the number of breaths taken within a minute, also increases because you are breathing faster. Both the respiration and heart rate have to increase in order to supply the needed oxygen to the body. If the respiration rate increased, but the heart rate did not, then the usual amount of oxygen would get to the body. If the heart rate increased and the respiration did not, the deoxygenated blood (blood without oxygen) would go out to the body rather than oxygenated blood (blood with oxygen).

Smoking:

Smoking also affects the respiration of the smoker and any person around the smoke. Cigarette smoke damages the alveoli when inhaled. Damaged alveoli are no longer able to participate in gas exchange. We normally have about 300 million alveoli completing gas exchange for us. The high number of alveoli gives us a much larger area for gas exchange to meet the needs of the body. This surface area is decreased when alveoli are damaged by smoking. 

Smoking can also lead to the development of lung cancer and heart disease. Lung cancer is a disease that results from an overgrowth of lung tissue that affects the ability to exchange gas. Cancerous alveoli and lung cells do not perform the function of normal alveoli, decreasing the amount of respiration occurring in the lungs. 

 

The Need For Gas Exchange

Gas exchange allows the body to replenish the oxygen and eliminate the carbon dioxide. Doing both is necessary for survival.Cellular respiration is the process by which cells convert energy rich molecules (food) into a form of energy that is easily utilized by cells, called ATP. Aerobic respiration yields large amounts of cellular energy (ATP) but requires oxygen. Carbon dioxide is produced as a waste product. Efficient gas exchange ensures enough oxygen is supplied / carbon dioxide is removed in order to maintain cellular energy levels.

Requirements For Efficient Gas Exchange

Moist Surface

Efficient gas exchange relies on a moist surface as oxygen must first dissolve into water before it can diffuse through a cell membrane. 

Concentration Gradient

 

Cellular respiration ultimately relies on the diffusion of oxygen into the cell and carbon dioxide out of the cell. Diffusion is the net movement of particles down their concentration gradient. In order for oxygen to diffuse into the cell there must be a higher concentration outside the cell. Similarly, in order for carbon dioxide to diffuse out of the cell there must be a lower concentration of carbon dioxide surrounding the cell. 

Thin and Permeable Membrane

The gas exchange surface needs to be thin in order to reduce the distance over which gasses have to diffuse.

Large Surface Area to Volume Ration (SA:VOL)

The greater the surface area that is in contact with the environment, the greater the rate of diffusion (increases the rate of oxygen supply and carbon dioxide removal). However, increasing volume increases oxygen demand and the diffusion distance from the surface to the center. Gas exchange structures increase the SA:Vol to ensure oxygen supply is sufficient to meet the organisms oxygen demands. It also ensures that carbon dioxide is released at a greater rate than it is produced (a build up of carbon dioxide within the cells would be toxic).As an organism increases in size its volume increases more rapidly than it's surface area. The small size of singled celled organisms ensures they have a great enough SA:Vol ratio to satisfy their needs. Larger organisms rely on gas exchange structures that increase their surface area without significantly increasing their volume.

 

TISSUE RESPIRATION

The term tissue respiration denotes the exchange of respiratory gases within an aggregation of cells in the course of the biological oxidation of nutrients. The oxygen received by the cells from the capillary blood is consumed in oxidative metabolism, and at the same time the metabolic end product carbon dioxide is released into the capillary blood.  

Tissue respiration also called internal respiration), the aggregate of enzymatic processes occurring during the absorption of atmospheric oxygen in the cells of organs and tissues. The products of the breakdown of carbohydrates, fats, and proteins subsequently become oxidized into carbon dioxide and water, and a large amount of the released energy is stored in the form of high-energy compounds. Tissue respiration differs from external respiration the aggregate of physiological processes that take oxygen into the body and eliminate carbon dioxide. Many enzymes that catalyze these processes are located in cytoplasmic organelles called the mitochondria.

All manifestations of life growth, movement, excitation, and reproduction consume energy. The form of energy used by cells is the energy of the chemical bonds in high-energy compounds, mainly such phosphates as adenosinetriphosphate (ATP). An intake of energy from external sources is necessary for the synthesis of ATP. The principal difference between an autotrophic and heterotrophic organism is the organism’s method of obtaining energy. The cells of green plants the most typical autotrophes use solar energy for the synthesis of ATP and glucose during the process of photosynthesis. Within plant cells, more complex molecules are formed from glucose during tissue respiration. In the cells of heterotrophes animals and man energy is derived solely from the molecular chemical bonds of food substances. The molecules of various compounds function as biological fuel and include glucose, fatty acids, and some amino acids. These molecules are formed in the cells or enter the blood from the digestive tract; they subsequently undergo a number of chemical changes.

 

PROCESSES IN TISSUE RESPIRATION

There are three basic stages in the process of tissue respiration;

The first consists of the oxidation formation of acetyl coenzyme A (an active form of acetic acid) from pyruvic acid (an intermediate product of glucose breakdown), fatty acids, and amino acids.

 The second stage involves breakdown of acetyl residues during the tricarboxylic acid cycle and the release of two molecules of carbon dioxide and four pairs of hydrogen atoms. The latter are partly accepted by the coenzymes nicotinamide adenine dinu-cleotide and flavin adenine dinucleotide, and partly become dissolved into protons.

The third stage consists of the transfer of electrons and protons to molecular oxygen (the formation of H₂O), a process that is catalyzed by a set of respiratory enzymes and is conjugated with the formation of ATP. This catalysis is known as oxidizing phosphorylation. The first two stages are a preparation for the third, during which most of the energy produced in the cell is released owing to oxidation-reduction reactions. Approximately 50 percent of the energy resulting from oxidizing phosphorylation is stored in the form of high-energy ATP bonds; the remainder is released as heat.

 

IMPORTANCE OF TISSUE RESPIRATION

Tissue respiration ensures the formation and constant replenishment of ATP in the cells. When the supply of oxygen to the cells of animals and man is insufficient, the reserves of ATP are not immediately exhausted. They may be replenished through such auxiliary mechanisms as glycolysis (The breakdown of glucose into pyruvate, ATP, H₂O, and heat.) and glycogenolysis ( breakdown of the molecule glycogen into glucose, a simple sugar that the body uses to produce energy.) that is, the anaerobic breakdown of carbohydrates. However, in terms of energy, this method is far less efficient and cannot ensure the functioning and structural integrity of the organs and tissues. The biological role of tissue respiration extends beyond its already significant contribution to the energy metabolism of the organism. During different stages of tissue respiration, molecules of organic compounds are formed that are used by cells as intermediate products for various biosyntheses.

 

 

 

 

 

 

 

 

 

 

CHAPTER 7

TEACHING ABOUT THE DIGESTIVE SYSTEM

 

DIGESTION

Digestion is the chemical and mechanical breakdown of food substances into smaller components that are more easily absorbed into blood streams.

Mechanical digestion involves the breakdown of solid foods into smaller pieces by the chewing action of the teeth, the churning of the stomach and the peristalsis of the oesophagus.

Chemical digestion takes place once food is chewed and broken down in the digestive tract where enzymes are used.

Enzymes are biological molecules (typically proteins) that significantly speed up the rate of chemical reactions that take place within cells. They are vital for life and serve as a wide range of important function in the body, such as aiding in digestion and metabolism. Some enzymes break large molecules into smaller pieces that are more easily absorbed by the body. Other enzymes help bind two molecules together to produce new molecule. Enzymes are highly selective catalysts, which means that, each enzyme speeds up a specific reaction. The following are some enzymes and their function;

i. Amylase converts cooked starch to glucose.

ii. Protease enzymes converts protein to amino acids.

iii. Lipase converts lipids (fats and oil) to fatty acid and glycerol.

iv. Sucrose converts sucrose to glucose and fructose.

v. Lactase converts lactose to glucose and galactose.

vi. Erepsin converts peptides to amino acids.

 

DENTITION

Dentition is the characteristic type, number and arrangement of teeth in the lower and upper jawbone in an animal. Dentition is related to the type of food the animal eats. Where the teeth of an animal are of the same type and shape, they are termed as homodont dentition. Such examples are found in vertebrates such as reptiles, fishes and amphibians. However, where the teeth of an organism are of different size and shape as found in mammals, they are termed as heterodont dentition.

 

The Structure of a Teeth

   

 

 

 

All true teeth have the same general structure and consist of three layers. In mammals an outer layer of enamel, which is wholly inorganic and is the hardest tissue in the body, covers part or all of the crown of the tooth. The middle layer of the tooth is composed of dentine, which is less hard than enamel and similar in composition to bone. The dentine forms the main bulk, or core, of each tooth and extends almost the entire length of the tooth, being covered by enamel on the crown portion and by cementum on the roots. Dentine is nourished by the pulp, which is the innermost portion of the tooth. The pulp consists of cells, tiny blood vessels, and a nerve and occupies a cavity located in the center of the tooth. The pulp canal is long and narrow with an enlargement, called the pulp chamber, in the coronal end. The pulp canal extends almost the whole length of the tooth and communicates with the body’s general nutritional and nervous systems through the apical foramina (holes) at the end of the roots. Below the gumline extends the root of the tooth, which is covered at least partially by cementum. The latter is similar in structure to bone but is less hard than dentine. Cementum affords a thin covering to the root and serves as a medium for attachment of the fibers that hold the tooth to the surrounding tissue (periodontal membrane). Gum is attached to the adjacent alveolar bone and to the cementum of each tooth by fiber bundles.

 

The different types of teeth are;

a. Incisors which are shaped like chisel and with sharp flat edges for cutting off pieces of food.

b. Canines which are long, conical and bluntly pointed used for tearing flesh.

c. Premolars, they have a broad crown with a number of projection called cusps. They are used for chewing (grinding) crushing bones.

d. Molars appear in permanent dentition only. They are broad and cusped and are used for chewing food and crushing bones.

The premolars and molars are collectively called cheek teeth.

 

There are successions of two sets of teeth in the life of every mammal, these are;

1. Milk or deciduous teeth: they are the first set of teeth and are small and short-lived. They occur as incisors, canines and premolars. The teeth are shed off between the ages of 5-7 years as their roots dissolve away in the jaw. There are twenty milk teeth in man.

2. Permanent dentition: these teeth grow to replace the milk teeth and comprises of incisors, canines, premolars and molars. They are thirty-two in human.

Dental formula

It is numerical representation of the number, type and arrangement of teeth in any mammal. Usually, it is either the right or the left side of the jaw which is represented in the formula. The total number of teeth in man is represented in the dental formula below;

2(I²₂ C₁¹ PM²₂ M₃³) = 32

Where the initials I, C, PM and M stand for incisors, canines, premolars and molars respectively. So the total number of teeth in man is obtained by adding the number and multiplying the sum by 2.

       

 

DENTITION IN ANIMALS

Animals can be put into three groups, according to the type of food they eat. The groups are:

1. Carnivorous

2. Herbivorous.

3. Omnivorous.

CARNIVORE DENTITION

A carnivore is an animal that feeds on flesh of other animals only. Carnivorous animals subsist on the flesh, bones, and viscera of other creatures. Most carnivores have long, sharp teeth adapted to ripping, tearing or cutting flesh. While many also possess a few molars in the back of their mouths, and sharp incisors in the front, the most important teeth for carnivores are their long, sharp canine teeth. Carnivores drive these teeth through the flesh of their prey with the help of very large temporalis muscles, which are responsible for pulling the lower jaw upwards and backwards towards the skull. The temporalis muscles attach to the jaw at one end, and the top of the skull at the other end. To help accommodate larger temporalis muscles, some predators have evolved to have an enlarged ridge, termed the sagittal crest that acts as an attachment point or anchor for the muscle.  

Dentition in carnivore

However, the sagittal crest is not exclusively limited to carnivores, as it also appears in many herbivorous primates as well. Additionally, because predators must capture and kill their food before they can eat it, some possess teeth that aid in prey capture. Cats, for example, use their four, long canine teeth to sever their prey’s spinal cord. Some snakes have even more specialized prey-capturing teeth that have evolved into hypodermic-needlelike fangs to deliver venom into their prey.

 

HERBIVORE DENTITION

Herbivores survive by consuming plant material. While some are indiscriminate grazers that consume a variety of plants, others are specialists that only eat a single plant species. For example, goats may eat virtually any vegetation they encounter, but koalas subsist entirely on eucalyptus plants. In general, plant foods are difficult to breakdown and digest; so, many herbivores have several pairs of broad molars that they use to grind leaves, shoots, and twigs. Often, herbivores feature ridged molars and jaws capable of moving sideways. Both of these traits help herbivores to grind their food more effectively. Most herbivores are missing canines entirely, and those that do possess them usually have very small or reduced canines that are not very important for chewing food. Some herbivores have large incisors for clipping or tearing vegetation, but they may only occur on the lower jaw. For example, most deer lack upper incisors and press their lower incisors against their hard, upper palate to rip twigs and branches from trees. By contrast, horses have both upper and lower incisors that they use to clip vegetation cleanly. Some herbivores have evolved teeth that are no longer involved in feeding

At all.

        

For example, the large tusks of elephants are highly modified incisors. Elephants use their tusks to manipulate items in their environment, dig for water, and defend themselves. Walruses and some pigs also feature incisors that have evolved into tusks used for foraging, defense, and intra-species combat.

 

OMNIVORE DENTITION

Omnivores, such as raccoons, opossums, bears, and humans, are animals that consume both plant and animal material. Accordingly, omnivores have dentition, skulls, and teeth suitable for handling a variety of foods. Most omnivores have evolved different types of teeth, located in °different parts of their mouths. In such scenarios, each type of tooth excels at handling a different type of food. For example, humans use their incisors and canines for ripping and cutting, and their molars and premolars for grinding. Biologists describe animals with such teeth as having heterodont dentition. By contrast, the teeth of homodont animals, such as iguanas, are all the same shape. As with some carnivores that have teeth to aid in prey capture, some omnivores have teeth that help them to obtain, rather than process, their food. Rodents are famous for their long, continuously growing incisors, which they use to chew through husks, shells and wood. This allows them to access well-protected or difficult-to-access foods, such as nuts. Although rodents are omnivores that occasionally eat insects and scavenge carcasses, plant material makes up the bulk of their diet. Their dentition reflects this as well: Rodents have strong molars, yet lack canine teeth entirely. Instead, rodents have a gap between their incisors and molars, termed a diastema. An example of omnivore is man.

 

 

Dental disease

They are disease that may affect the teeth, gum or tissues and part of the mouth. The most common dental disease in human are dental caries (tooth decay), periodontal disease (gum diseases) and pyorrhea.

i. Dental caries (tooth decay)

It is an infection caused by bacteria that causes demineralization and destruction of the hard tissues (enamel, dentine and cement) usually by production of acid by bacterial fermentation of the debris accumulated on the tooth surface and create cavities in tooth. If not treated it can cause pain, infection and tooth loss.

ii. Periodontal diseases (gum disease) 

It refers to infection of the gum and bone that surround and support the teeth. At its early stage, it is called gingivitis, the gum becomes swollen, red and may bleed. In its more serious form, it is called periodontitis, the gum can pull away from the tooth. When this happens the cement is exposed and the fibers holding the tooth becomes loss and tooth may fall out.

iii. Pyorrhea

It is a disease of the gum and affect the membrane surrounding the roots of the tooth and lead to losing of the teeth and shrinkage of the gum. It is the primary cause of the tooth loss in adult. The gum becomes swollen and tender and pus may ooze. Pyorrhea is triggered by bacterial activity which can produce many toxins.

 

Dental diseases are caused by the following

1. Bacteria

2. Lack of hard food

3. Too much sweet food

4. Lack of calcium or phosphorus in diet

5. Lack of vitamin A, C or D

6. Improper cleaning of teeth

7. Lack of massage of the gum

8. Eating very hot or cold food

Dental Care: It is the maintenance of heathy teeth.

How to care for the teeth in human

1. Teeth should be brushed at least twice a day

2. Use personal brush to avoid spread of disease

3. Avoid opening bottles with your teeth

4. Tooth paste containing fluoride should be used

5.  Avoid eating too much hot or cold food

6. Avoid eating too much sugary food

7. Brush your teeth according to the direction they grow

 

 

Types of digestion

1. Mechanical digestion involves the breakdown of solid foods into smaller pieces by chewing action of the teeth, peristalsis of the oesophagus and the churning of the stomach walls.

2. Chemical digestion involves the secretion of enzymes on mechanically digested food throughout the digestive tract.

Processes that happened in the digestive system

1. Ingestion is taking food into the body.

2. Digestion is the breakdown of complex food substances into simpler unit that can be absorbed into the blood stream  

3. Absorption is the uptake of simple molecules into the living cell.

4. Egestion is the discharge of unabsorbed and undigested component.

Ingestion                 Digestion              Absorption               Egestion

The digestive system in mammal consist of the elementary canal (the gut and its associate glands and organs) the elementary canal is made up of the mouth, oesophagus, stomach, small intestine and large intestines. The associated structures include the teeth, liver, pancreas, salivary gland and gall bladder. The associate structures aid in breakdown of food either mechanically or chemically by secreting enzymes. The liver and gall bladder produces and stores bile respectively.

Digestion in the mouth

In human body, the mouth is a specialized organ for receiving and breaking down large organic masses. In the mouth, solid food is chewed or masticated by teeth into smaller particles to provide large surface area for enzymes action. The salivary gland in the mouth produces saliva into the mouth. The components of the saliva are mucus, salt, enzymes (salivary amylase) and water. The saliva plays four main functions in the digestion of food.  These are;

1. It provides mucus that binds food particles together into soft mass.

2. It mixes thoroughly with the food during chewing making it soft and easier to swallow.

3. The saliva contains salivary amylase or ptyalin which digest starch molecules into smaller molecules of the disaccharide maltose.

4. The alkaline nature of saliva provides the correct pH for salivary amylase action. During chewing, the tongue moves food about and manipulate it a mass called bolus.  The bolus is pushed back into the pharynx and is forced through the opening of the oesophagus. The tongue tastes the food, mixes it and rolls the food into balls called bolus for swallowing.

Swallowing and movement of food in the gullet (oesophagus)

The oesophagus is thick-walled muscular tube that extends through the neck and chest to the stomach. The bolus of the food moves through the oesophagus by force of gravity and peristalsis.

Digestion in the stomach

A valve-like ring of muscle called cardiac sphincter which surrounds the opening of the stomach. The stomach is an expandable muscular bag located high in the abdominal cavity. Layers of the stomach muscle contract and churn the bolus of food with gastric juice to form a creamy-like liquid called chime. The stomach performs the following functions;

1. The giblet cells in the mucosa secrets mucus that protects the walls of the stomach against hydrochloric acid.

2. The hydrochloric acid produced by the stomach walls provide correct acidic medium for the action of the enzyme pepsin. It also sterilizes food by killing harmful bacteria and also stops the action of Amylase.

3. The gastric gland secrets pepsinogen which is converted to the enzyme pepsin in the presence of hydrochloric acid. The pepsin digest large proteins into smaller proteins called peptides. The gastric juice secret an enzyme renin to coagulate milk proteins in the diet of young mammals. Relaxation of pyrolic sphincter allows the propulsion of chime into the small intestine. The pyrolic sphincter is a strong ring that surround the opening of the duodenum and allows food to pass from the stomach to the duodenum. Water and soluble substances with relatively small molecules are partly absorbed.

 

                 Digestion in the small intestine

The chime passes from the stomach through the pyrolic sphincter into the small intestine. An adult small intestine is about 23 feet long and is divided into three; duodenum jejunum and ileum.

When chime reaches the duodenum, the hormone secretin stimulates the pancreas and gall bladder to produce pancreatic juice and bile respectively. The bile stops the action of pepsin and emulsifies fats. Emulsification increases the surface area of fat making the action of lipase more efficient. The pancreatic juice contains several enzymes such as amylase, trypsin and lipase which become active in alkaline bile in the duodenum. The food then passes into the ileum for final digestion and absorption.

The food moves into the large intestine for absorption of water to take place. The intestinal matter remaining after water has been reclaimed is known as faeces which comes out through the anus.

 

ENZYMES

Enzymes are protein compounds. They are biological catalysts, manufactured by living cells to speed up metabolic reactions in organisms, without themselves being change in process.

 

Types Of Enzymes

1. Endoenzymes: they are enzymes which act within the cells that produce them. Examples: dehydrogenases and decarboxylases.

2. Exoenzymes: These are enzymes which are secreted from the cell that produced them to perform their functions. Examples: Amylase, pepsin, trypsin etc.

 

Characteristics Of Enzymes

1. They are proteins and therefore can destroy by temperature.

2. They are affected by pH, temperature, substrate concentration and enzyme concentration.

3. They are specific in their actions, that is an enzyme which acts on substrate will not act on protein or fat substrate.

4. Some enzymes require certain ions, example Mg, Cu, Zn and K for efficient working.

5. The efficiency of some enzymes is stepped up by the presence of certain enzymes called activators. Example:  Cl ion.

 

Factors That Affect Enzyme Action

1. Temperature: All enzymes have minimum, optimum and maximum temperatures for their activity; the precise range depend upon the size of enzymes. The effect of temperature on any reaction is to double it rate for every 10°C due to increase kinetic energy and consequent increase rate of collision of reactants. Extremes of temperature of either side of optimum, denature the enzymes disrupting the hydrogen bonds and electrostatic charges on active site.

2. PH: The PH scale is used to measure acidity or alkalinity of a solution and is the measure of the concentration of hydrogen ions. A PH of seven is neutral, below is acid and above is alkaline. Each enzyme work within a narrow PH range and has its own optimum. Amylase, sucrase and dehydrogenases all work best in slightly alkaline conditions. Extremes of PH on either side of the optimum denature the enzyme.

3. Substrate Concentration: Enzyme activity increases proportionally with increase substrate concentration until the maximum turnover rate achieved. This is due to increase chance of enzyme and substrate collision. Once the maximum rate is reached no further increase is possible as the rate is limited by the availability of active sites.

4. Enzyme Concentration: Enzyme activity also increase in direct proportion to enzymes concentration as more active sites are available. Collision between enzymes and substrate are also more likely as more enzymes are added; the rate is eventually limited by substrate availability.

5. Inhibitor: This influence the rate of an enzyme catalyzed reaction. Inhibitors such as cyanide can stop or slow down enzyme activity.

6. Co- enzyme: The efficiency of some enzyme is altered by the presence of certain ion called activator, for example Cl¯ is an activator for salivary amylase.

 

Digestive enzymes.

Digestive enzymes are released both in the anticipation of eating, when we first taste food, as well as throughout the digestive process.

 

 

 

Types of digestive enzymes

1. Each digestive enzymes targets a specific nutrient, splitting, it up into a form that can be absorbed by the body. The following are some of types of digestive enzymes.

2. Amylase: it is the essential for the digestive of carbohydrates or starch. Amylase break down starch into maltose. It is secreted by salivary glands. Amylase is known as ptyalin and works best in alkaline conditions.

3. Proteases: they are secreted by stomach and pancreas. Proteases work best in acidic conditions. Examples of protease are as follows.

a. Pepsin: it breaks protein into peptides.

b. Trypsin: it is secreted by pancreas and activates additional pancreatic enzymes such as carboxypeptidase and chymotrypsin to assist in breaking down peptides.

c. Chymotrypsin: it breaks down peptides into free amino acids that can be absorbed by small intestinal wall.

d. Carboxypeptidase: it breaks down and split peptides into individual amino acids.

e. Erepsin: it converts liquid protein such as milk into solid form for pepsin to act on it.

4. Maltase: it is secreted by small intestine and responsible for breaking down maltose into glucose that the food uses for energy.

5. Lactase: it breaks down lactose that is sugar in dairy products glucose and galactose.

6. Lipase: it is produced by pancreas and responsible for the breakdown of fats and oil into fatty acids and glycerol.

7. Sucrase: it is secreted by small intestine where it breaks down sucrose into fructose and glucose.

 

 

 

 

 

 

CHAPTER 8

TEACHING THE ECOSYSTEM

The ecosystem is the structural and functional unit of ecology where the living organisms interact with each other and the surrounding environment. In other words, an ecosystem is a chain of interaction between organisms and their environment. The term “Ecosystem” was first coined by A.G.Tansley, an English botanist, in 1935.

 

Types of Ecosystem

An ecosystem can be as small as an oasis in a desert, or as big as an ocean, spanning thousands of miles. There are two types of ecosystem:

1. Terrestrial Ecosystem

2. Aquatic Ecosystem

Terrestrial Ecosystems

Terrestrial ecosystems are exclusively land-based ecosystems. There are different types of terrestrial ecosystems distributed around various geological zones. They are as follows:

1. Forest Ecosystems

2. Grassland Ecosystems

3. Tundra Ecosystems

4. Desert Ecosystem

 

Forest Ecosystem

A forest ecosystem consists of several plants, animals and microorganisms that live in coordination with the abiotic factors of the environment. Forests help in maintaining the temperature of the earth and are the major carbon sink.

Grassland Ecosystem

In a grassland ecosystem, the vegetation is dominated by grasses and herbs. Temperate grasslands, savanna grasslands are some of the examples of grassland ecosystems.

 

 

 

 

Tundra Ecosystem

Tundra ecosystems are devoid of trees and are found in cold climates or where rainfall is scarce. These are covered with snow for most of the year. The ecosystem in the Arctic or mountain tops is tundra type.

 

Desert Ecosystem

Deserts are found throughout the world. These are regions with very little rainfall. The days are hot and the nights are cold.

 

Aquatic Ecosystem

Aquatic ecosystems are ecosystems present in a body of water. These can be further divided into two types, namely:

1. Freshwater Ecosystem

2. Marine Ecosystem

Freshwater Ecosystem

The freshwater ecosystem is an aquatic ecosystem that includes lakes, ponds, rivers, streams and wetlands. These have no salt content in contrast with the marine ecosystem.

Marine Ecosystem

The marine ecosystem includes seas and oceans. These have a more substantial salt content and greater biodiversity in comparison to the freshwater ecosystem.

 

Structure of the Ecosystem

The structure of an ecosystem is characterised by the organisation of both biotic and abiotic components. This includes the distribution of energy in our environment. It also includes the climatic conditions prevailing in that particular environment. 

The structure of an ecosystem can be split into two main components, namely: 

· Biotic Components

· Abiotic Components

The biotic and abiotic components are interrelated in an ecosystem. It is an open system where the energy and components can flow throughout the boundaries.

 

 

 

 

 

Structure of Ecosystem highlighting the biotic and abiotic factors

Biotic Components

Biotic components refer to all life in an ecosystem.  Based on nutrition, biotic components can be categorised into autotrophs, heterotrophs and saprotrophs (or decomposers).

· Producers include all autotrophs such as plants. They are called autotrophs as they can produce food through the process of photosynthesis. Consequently, all other organisms higher up on the food chain rely on producers for food.

· Consumers or heterotrophs are organisms that depend on other organisms for food. Consumers are further classified into primary consumers, secondary consumers and tertiary consumers.

· Primary consumers are always herbivores that they rely on producers for food.

· Secondary consumers depend on primary consumers for energy. They can either be a carnivore or an omnivore.

· Tertiary consumers are organisms that depend on secondary consumers for food.  Tertiary consumers can also be an omnivore.

· Quaternary consumers are present in some food chains. These organisms prey on tertiary consumers for energy. Furthermore, they are usually at the top of a food chain as they have no natural predators.

· Decomposers include saprophytes such as fungi and bacteria. They directly thrive on the dead and decaying organic matter.  Decomposers are essential for the ecosystem as they help in recycling nutrients to be reused by plants.

Abiotic Components

Abiotic components are the non-living component of an ecosystem.  It includes air, water, soil, minerals, sunlight, temperature, nutrients, wind, altitude, turbidity, etc. 

Functions of Ecosystem

The functions of the ecosystem are as follows:

1. 

1. It regulates the essential ecological processes, supports life systems and renders stability.

2. It is also responsible for the cycling of nutrients between biotic and abiotic components.

3. It maintains a balance among the various trophic levels in the ecosystem.

4. It cycles the minerals through the biosphere.

5. The abiotic components help in the synthesis of organic components that involves the exchange of energy.

Important Ecological Concepts

1. Food Chain

The sun is the ultimate source of energy on earth. It provides the energy required for all plant life. The plants utilise this energy for the process of photosynthesis, which is used to synthesise their food.

During this biological process, light energy is converted into chemical energy and is passed on through successive levels. The flow of energy from a producer, to a consumer and eventually, to an apex predator or a detritivore is called the food chain.

Dead and decaying matter, along with organic debris, is broken down into its constituents by scavengers. The reducers then absorb these constituents. After gaining the energy, the reducers liberate molecules to the environment, which can be utilised again by the producers.

 

A classic example of a food chain in an ecosystem

 

2. Ecological Pyramids

An ecological pyramid is the graphical representation of the number, energy, and biomass of the successive trophic levels of an ecosystem. Charles Elton was the first ecologist to describe the ecological pyramid and its principals in 1927.

The biomass, number, and energy of organisms ranging from the producer level to the consumer level are represented in the form of a pyramid; hence, it is known as the ecological pyramid.

The base of the ecological pyramid comprises the producers, followed by primary and secondary consumers. The tertiary consumers hold the apex. In some food chains, the quaternary consumers are at the very apex of the food chain.

The producers generally outnumber the primary consumers and similarly, the primary consumers outnumber the secondary consumers. And lastly, apex predators also follow the same trend as the other consumers; wherein, their numbers are considerably lower than the secondary consumers.

For example, Grasshoppers feed on crops such as cotton and wheat, which are plentiful. These grasshoppers are then preyed upon by common mice, which are comparatively less in number. The mice are preyed upon by snakes such as cobras. Snakes are ultimately preyed on by apex predators such as the brown snake eagle.

In essence:

Grasshopper →Mice→  Cobra → Brown Snake Eagle

3. Food Web

Food web is a network of interconnected food chains. It comprises all the food chains within a single ecosystem. It helps in understanding that plants lay the foundation of all the food chains. In a marine environment, phytoplankton forms the primary producer.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CHAPTER 9

SCIENCE PEDAGOGY AND CURRIULUM

Brown began with the primary psychosocial tasks adolescents must accomplish.  there are four key tasks: that learners are supposed to perform

1. to stand out—to develop an identity and pursue autonomy,

2. to fit in—to find comfortable affiliations and gain acceptance from peers,

3. to measure up—to develop competence and find ways to achieve, and

4. to take hold—to make commitments to particular goals, activities, and beliefs.

He therefore identified two ways in which these basic tasks relate to the risks that adolescents take.

First, many risk behaviors can either foster or impede the successful accomplishment of these tasks.

Second, adolescents may turn to risky behaviors to help themselves cope with the failure to succeed in one of these areas.

Brown looked first at the relationship between risk-taking and the development of identity, which has been viewed by some psychologists as primarily an individual psychological process and by others as more of a social process. Researchers have identified other components that also play a part in identity formation, such as identification by gender, ethnicity, and sexual orientation. A part of the task for adolescents is to discern the criteria for these possible identities, evaluate them, and decide whether and how to incorporate them into their personal sense of self. If individuals develop a high sense of agency (taking responsibility for their own actions) while retaining close connections with significant adults, they are likely to develop a healthy “autonomous, relational self,” which is likely to result in relatively low risk-taking. When this process goes away, the result is often increased risk-taking. Finally, adolescents spend a lot more time with their peers than younger children do and are more heavily influenced by them than younger children are.

 

The Psychological Foundation of the Activity Method

The Activity Method has its basis in great work done by the Swiss Psychologist, Jean Piaget, on the Stages of Cognitive Development in Children. He put children into four developmental stages. These are:

i.  Sensori-Motor stage - (0-18 months)

ii. Pre-Operational stage - (2-7 years)

iii. Concrete Operational stage - (7-11 years)

iv. Formal Operational stage (11 + years)

 

According to Piaget, each stage has a distinctive behavioural pattern. At the Sensori-Motor stage, the child’s early activities appear to be purely reflexive in character. For example, sucking, grasping objects, kicking the legs and performing other bodily activities. Actions of the child are thus entirely involuntary, as there is no thinking involved. Later activities are out centred on the child’s own body. The child reaches out to manipulate objects in the environment. However, object permanence is weak. i.e.  an object ceases to exist if they cannot be seen. With time, object permanence becomes stronger and fully developed. There is also the beginning of symbolisation through imitation.

At the Pre-Operational stage, development of language of symbolic function, thought and representation continues but there is no idea of reversibility and conservation. The child employs both incomplete and illogical concepts and reasons transductively i.e. reasons from one particular instance to another particular instance. For example, the child calls a goat, a sheep, since both have similar features. The child is also egocentric. i.e. self-centred, sees the world only in terms of his own perspective. The child has no mental plan of a series of actions at this stage.

At the Concrete Operational stage, there is development of logical thinking but only about concrete objects. The child develops the ideas of conservation and reversibility and can only apply rules of logic to concrete objects and events. The child can also recognize and appreciate others points of view. The child also shows increasing memory skills and the ability to use hierarchical systems to classify and organize concepts.

At the Formal Operational stage, the child develops the ability to think hypothetically and in abstract terms. The child’s thought process becomes quite systematic and reasonably well integrated.

 

The Implications of Piaget’s Stages of Cognitive Development to the Teaching and Learning of Science at the Basic Schools

The Instructional Method employed by the science teacher should take into consideration the abilities and skills already acquired. The teacher should be aware of the developmental stage at which each child is functioning and each should be taught only what the child is ready to learn.

The science teacher should act as a guide working with the child as he interacts with the environment, ensuring that experiences are appropriate for the stage at which the child is functioning.

Science teachers in the basic schools should provide a lot of concrete materials objects and encourage their use by pupils in suitably designed activities to help them develop manipulative skills, make their own discoveries, classify, construct and analyses materials. These enable pupils to develop cognitive skills such as perceptions, conceptions, reasoning, memory and creativity.

Science teachers at the upper level of the basic school, i.e. J.H.S. should provide activities that are challenging and problems that would enable the pupils to make hypothesis in finding solutions to such problems.

.

INSTRUCTIONAL PLANNING

 LESSON PLAN

There are three phases of planning. These are:

GENERAL PLANNING

In general planning, the work of the whole year is broken into 3 terms for any particular class. This is what is found in the integrated science and Science Syllabus for each class respectively.

  UNIT PLANNING

In unit planning, each topic to be taught in a term is broken into manageable parts in a lesson or more lessons called a unit and a week or two assigned to each unit. This is what is referred to as Scheme of Work.

The scheme of work is thus a plan, which ensures that the content of the syllabus provided for a certain period of time i.e. a term, is taught within that period. It entails the arrangement of the units/topics in such a way that those that provide pre-requisite learning are placed before subsequent ones. The number and/ or duration of periods allotted to a particular subject area on the timetable determines what goes into the unit.

In drawing up a scheme, the number of working weeks, the syllabus, facilities, age and ability of the pupils, materials available and the size of class must be taken into consideration. In addition, the teaching methods or strategies to be employed have to be decided on by the individual trainees.

There are 6 columns in the format for preparing a scheme of work with the following headings.

 

Week	Topic/unit	Ref.	T.L.M	Advanced Preparation	Remarks

The advance preparation column entails whatever is done in terms of preparation to teach the topic/unit in the classroom.

The remark column also plays a vital role. In it, what takes place in the teaching-learning process during the week is recorded. This brings into focus the need to design all subsequent units only after the previous ones have been taught.

 

IMPORTANCE OF A TERMLY SCHEME OF WORK

The termly scheme of work helps the teacher to:

. Plan the topics that are to be covered in the term, and can

determine the amount of work to do in the term.

Determine whether he/she is lagging behind or moving forward in

His/her teaching programme

It enables any new teacher who takes over from the class teacher in

the middle of the term to determine where to begin or continue the lessons from.

If properly planned and executed, it serves as a record of work for

the period.

WAYS OF ESTABLISHING TEACHING ORDER

The sequence of topics is often derived from the syllabus or a list of issues to be taught. There are, however, several ways in which you as a trainee can establish your own teaching order. Some of these are:

EASIEST TOPICS FIRST. In this way you can gain the confidence of pupils before addressing the more difficult issues/topics.

THE THEME. Some courses can be seen in terms of themes and two or more themes make up the scheme of work. For example, personal hygiene theme, body cleanliness theme.

LOGICAL SEQUENCE. In some topics e.g. plants, flowers and leaves are taught before stems and roots so it is logical to have that sequence.

BEGINNING WITH FAMILIAR TOPIC. You may be familiar with only part of the syllabus and teaching what you know allows you time to prepare well for the other topics.

HISTORICAL/ CHRONOLOGICAL ORDER. Certain topics are such that their natural divisions are chronologically arranged. This is a logical and natural teaching order. E.g. in treating diseases, the following order is used causative agent, sources of infection, mode of transmission, symptoms and prevention/control.

                                   

 LESSON PLANNING

In lesson planning, a short, carefully developed and usually written outline is designed to help the teacher to achieve the objective of a specific topic, skill or idea which could be part of a particular scheme of work. Information can be obtain form sources like the Integrated Science and Science syllabuses, and science textbooks and teacher’s manual etc.

Careful planning and thorough preparations are necessary preparations re-requisite for a successful and effective science lessons. The teacher-trainee should specifically know what to teach and how to teach it.

Lack of lesson planning can result in the following:

Omission of important elements of a lesson.

High likelihood of facts being inaccurate

Poor use of time during lesson presentation.

Lack of illustrative details.

Possibility of boredom and restlessness on the part of pupils.

Lack of logical presentation of subject matter.

Excessive correction during marking of children’s work.

 

POINTS TO CONSIDER IN PLANNING A SCIENCE LESSON

In planning a science lesson, the following points should be considered:

Consult the syllabus/ scheme of work to enable you know what to teach.

Define your objectives taking into account the nature of the subject matter, level of the pupils, their previous knowledge, time available and methodology to be employed.

Materials should be collected and stored for the lesson.

Activities designed and /or selected from the syllabus should be tried out with the materials collected.

Write your lesson plan or notes.

 

Note, however, that it is not the lesson note that actually teaches the lesson but you the teacher. It is therefore a bad practice to go on with a lesson, which is obviously unsuitable just because the lesson notes were made for that lesson. You may find, for example that part of the previous knowledge assumed is not in fact present. You will have to modify your lesson accordingly.

When planning the lesson, it is advisable to keep in mind the fact that the attention span of pupils, especially those in the primary school is limited and is therefore unwise to spend too much time on anyone activity. Even practical work should not be allowed to drag on too long. The best plan for a science lesson for a given period is to alternate activities.

Example:

Questioning to relate P.K. to present lesson.

Short description of work to be done

Experiment/ Activity

Discussion of results of experiment/ activity.

Explanation of theory arising from results etc.

Evaluation

 

G.E.S. APPROVED LESSON FORMAT USED ON THE TEACHING FIELD

WEEKENDING REF:

SUBJECT:

CLASS

SECTION:

DAY/ DURATION	Strand	Content standard	T.LA/T.L.R	CORE competencies
		QUOTE SYLLABUS REFERENCE NUMBER

REMARKS:

IMPORTANCE OF LESSON NOTE FEATURES

Strand

Helps in choice of methodology

Serves as a guide

Helps in systematic teaching.

Helps in evaluation/assessment.

Aids in selection of content.

Helps in selection of materials.

 Entry behavior

 

Helps in selection of materials

Helps to arouse and sustain interest of pupils in new lesson.

Helps in the selection of suitable activities.

A new lesson usually develops from it.

Helps in selection of teaching /learning aids.

 

TLR/TLA

Help develop manipulative skills.

Enable pupils learn better through first-hand experience.

It helps pupils avoid rote learning.

Help teachers to avoid drill-oriented methods.

Ensure maximum pupils’ participation in the lesson.

It demystifies science

It enhances/ promotes creativity/curiosity in pupils.

It promotes familiarity with materials in the environment.

 

INTRODUCTION.

Helps in preparing pupils for the lesson.

Provides conducive environment.

Helps in linking previous knowledge

Helps concretize previous knowledge.

Helps eliminate misconceptions in the P.K.

Focuses minds of learners towards a particular direction.

 

Indicators and examplar

Serves as a subject matter for the teacher.

Serves as notes for the pupils/major main ideas of lesson.

Evaluation is based on it.

vi. APPLICATION

Relate lesson to everyday life of pupils.

Relate concept in one subject area to another.

Helps in problem solving.

Test validity of generalization arrived at by learners.

Concretizes learning or reinforces learning.

 

CLOSURE/EVALUATION

Helps to ascertain whether objectives have been achieved or not.

Helps to ascertain whether pupils have understood the lesson or not.

Helps to identify areas of difficulty.

Helps teacher to draw up remedial lesson.

Helps to find out if the methodology used was appropriate or not.

 

NOTE: During OCTP the following preamble should be used:

WEEKENDING

SCHOOL NO. ON ROLL

SUBJECT: AVERAGE AGE

CLASS: REF.

              

Content standard	Indicators and exemplars	Core competencies

 

In using this format, the following should be taken care of:

1. After stating the day/ duration and the topic/subtopic, you should first state the

    TLR in the fourth column.

2. The RPK should be stated first in the third column and should be aligned

    horizontally with the introduction stage in the fourth column.

3. The Objectives should be stated after the RPK and be aligned horizontally with

    the development stage in the fourth column.

4. Each specific objective should be aligned horizontally with the

    activity/activities, which the learners would be engaged in.

5. The activity/activities should be aligned horizontally with the appropriate core

    point(s) in the fifth column and the evaluation exercises in the sixth column

6. Allocate time for each stage of the lesson

7. Don’t forget to write your remarks after the lesson below the evaluation

    exercises in the sixth column

 

PRESENTATION SKILLS AND GOOD PRACTICES IN SCIENCE TEACHING

There are four stages in the presentation of a science lesson. These are as follows:

i. INTRODUCTION

This stage often links the previous knowledge of the pupils with the material of the new lesson. This can be done through several means such as questioning, use of films or filmstrip leading to the subject, presenting problems, which require pupils to draw on the previous knowledge. This approach is based on the idea that learning is more effective if the new or unknown is linked to the old or known.

One important element of lesson presentation is introduction. It should be interesting and captivating. In many cases, the review of the previous knowledge constitutes the content of the introduction. However, there is no hard and fast rule about this. The previous knowledge if used in introducing the lesson, should be relevant to the new learning situation but need not be necessarily on the new topic. It should, however, be applicable to the new learning situation.

The introduction should do one or more of the following:

Create a desire in the pupils to participate in the lesson i.e. motivate the pupils.

Create an atmosphere conducive to the attainment of the objectives of the lesson.

Provide a link between the known and the unknown i.e. the old and the new materials.

Arouse interest and capture attention of the pupils.

Present a problem for which a solution is sought in the new lesson.

 

Introduction can be done effectively through questioning. This directs the thinking processes of the pupils along the required directions. Effective questioning can also be used to brainstorm the minds of the pupils for the effective take off of the lesson.

ii. DEVELOPMENT/PRESENTATION

This stage is the main body of the lesson. It is divided into steps, the number of which depends upon the topic and naturals divisions within it. Each step is approached differently depending on the content of that step and the specific objectives the teacher has. The trainee’s knowledge of various methods is called into play at this stage. It is, however, important that the teacher trainees tailor the information or activities they present to the level of cognitive development of the pupils.

iii. APPLICATION

During this stage, concepts, ideas, principles, rules taught is demonstrated to show understanding. This may occur during the presentation itself or may take place after the lesson in the form of exercises, problems to solve, expression of ideas or opinions or practical work.

iv. CLOSURE.

This is the last stage in the teaching of a science lesson. It can be done by several means such as review on lesson, discussion of results, and summary of lesson, evaluation and tidy up of the room.

GROUPING THE learners

Group work is very important in any science lesson. Grouping may be based on pupil’s ability, interest and age, and may be made up of 2-5 pupils. When the group is made up of the same ability, pupils are able to work at their own speed. They are given the opportunity to contribute actively to the lesson. It also brings about keen competition among them, develops a sense of responsibility in pupils and induces them to work hard.

Mixed ability grouping gives opportunity for the development of leadership skills and social sense, the stronger helping the weak. Group activities inculcate in the pupils the sense of cooperation and tolerance. Pupils tend to learn and share ideas amongst them selves. Finally, grouping enable limited resources available to be used effectively for the lesson

THE METHODOLOGY TO BE ADOPTED

The conducting of an activity lesson do not necessary mean only the activity method needed to be used throughout. Experience have shown that the most effective teaching include several methods, all employed during a single lesson or period. Student teachers are strongly advised to be mindful of this fact, and use the most appropriate method as the situation demands.

THE CONCLUSION OF THE LESSON

The conclusion of the lesson could be devoted to summary, revision, and evaluation of the lesson or pupils doing some exercises. It should also be properly linked with a future lesson.

  

GOOD PRIMARY PRACTICES IN LESSON PLANNING AND

 DELIVERY IN SCIENCE TEACHING

These are certain basic practices that one need to acquire to help enhance the teaching and learning effectively before, during and after a science lesson

Primary Practice Before a Lesson - (Pre-Delivery Activities).

i. Preparation of a comprehensive scheme of work for the term with a systematic arrangement of topics.

ii. Effective use of the three (3) basic curriculum materials namely the syllabus, pupil's textbooks and teacher's guide as well as other reference books.

Consulting resource personnel where necessary for information.

iv.        Considering the age of the pupils during the selection of teaching - learning material.

iv Selecting appropriate R. P. K for the topic.

v. Considering the duration and the time budget of the lesson.

vi. Preparation of improvised materials and teaching and learning materials.

vii  Statement of specific objectives, which are achievable, measurable and observable

             suitable to the level of the class performed by the pupils

viii.      Discussion on the activities. which did the pupils perform

ix         Selection of teaching and learning activities that will help the pupils to

develop the necessary process skills: and acquire scientific knowledge (core points)

x. Preparation of worksheets/ cards for the practical activities before the c I ass.

xi Mastery of the concepts and facts to be presented.

xii Preparation of a good lesson plan.

Good Primary Practices During a Lesson (Delivery Activities)

  i Very good introduction to link the topic with the RP.K.

  ii.       Grouping of pupils (at most five pupils in a group) for group work and group

            discussion based on something to be discussed or experimented to come out with

             their own findings or inferences.

   iii        The use of activity method of teaching together with other methods like

              discussion, demonstration, question and answer etc to achieve the stated objectives

               and to derive the core ideas.

    iv.        Giving clear and precise instructions during an activity lesson

     v.        Effective use of questioning skills i.e. using probing questions, distributing

                 questions evenly etc

vi        Being sensitive to gender issues during lesson delivery.

vii      Acting as a co-learner, a supervisor and a facilitator during an activity based

                lesson

     viii.    Taking safety measures during an activity based lesson.

     ix       Sequencing of core points during general class discussion on the activities which

                were performed by the pupils

    .x       Sustaining pupils' interest in the lesson by the use of reward and praises

     xi.   Good class control against unnecessary noise during an activity-based lesson.

    xii. Very clear and audible voice together with legible handwriting on the chalkboard

   xiii. Using English Language and local language side by side to explain difficult

             concept especially at the lower primary school

   xiv.    Standing at positions that pupils can see and hear from you.

   xv.     Catering for individual differences among the pupils.

  xvi.    Application of scientific concepts, facts and ideas learnt to real life

             situations.

Good Practices after a Lesson. {Post Delivery Activities}

Gathering the materials and cleaning the tables after practicum activities.

Evaluation of the lesson which can take the form of:

Drawing and labeling of objects.

Doing a. short exercise based on the activities ..

\Writing chalkboard summary

Assigning a project work.

Marking and recording of marks.

Evaluating the lesson taught and writing the remarks

Discussing feedback with pupils after they written an assignment.

 

 Lesson Evaluation

Lesson evaluation is meant to find out whether the teacher has achieved the stated lesson objectives or not. This can be done effectively by evaluating the methods of teaching and pupils' learning. Evaluation can be done effectively by answering the following questions.

Ø Did I review the previous knowledge of my pupils?

Ø Did I link the previous knowledge to the new topic?

Ø Did I involve all the pupils in the lesson?

Ø Did I present my materials sequentially?

Ø Did I make effective use of teaching-learning materials?

Ø Did I help the pupils to understand the materials I presented?

Answers to these questions will help to evaluate the method of teaching

 

 Another area of lesson evaluation is assessing pupils' achievement. This deals with how pupils have understood and can apply what have been taught them. Evaluation can also be done effectively by using class tests, questions, quizzes, examinations and homework. This means that you as a trainee must learn how to set and use the various methods of assessment