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The worms sometimes wander along the alimentary canal and may pass through the nose or mouth. In this way, they interfere with breathing and may cause serious illness. The larvae may cause severe internal bleeding as they penetrate the wall of the intestine.

Adaptive Characteristics The female lays as many as 25 million eggs. This ensures the continuation of the species. Eggs are covered by a protective cuticle that prevents them from dehydration.

The adult worms tolerate low oxygen concentration. Have mouth parts for sucking food and other fluids in the intestines. Has a thick cuticle or pellicle to protect it from digestive enzymes produced by the host. Control and Prevention Personal hygiene e.

Proper disposal of faeces. Washing of fruits and vegetables. Schistosoma Schistosoma or bilharzia worm is a flat worm, parasitic on human beings and fresh water snails.

Biomphalaria and Bulinus. The snail act as intermediate host. Mode of Transmission Schistosomiasis also known as a bilharsiasis is caused by several species of the genus schistosoma.

Schistosoma haemotobium is common in East Africa where irrigation is practised and where slow moving fresh water streams harbour snails. It is spread through contamination of water by faeces and urine from infected persons. The embryo miracidium that hatch in water penetrates into snails of the species Biompharahia and Bulinus. Inside the snail's body, the miracidium undergoes development and multiple fission to produce rediae.

The rediae are released into the water and develop to form cercariae which infect human through: Drinking the water Wading in water; Bathing in snail-infested water. The cercaria burrows through the skin and enters blood vessel. Effects on the host Inflammation of tissues where egg lodge. Ulceration where eggs calcify. Egg block small arteries in lungs leading to less aeration of blood.

The body turns blue - a condition known as cyanosis. If eggs lodge in heart or brain, lesions formed can lead to death. Bleeding occurs as the worms burrow into blood vessels faeces or urine has blood.

Pain and difficulty in passing out urine. Nausea and vomiting. When eggs lodge in liver ulceration results in liver cirrhosis. Death eventually occurs. Adaptive Characteristics The female has a thin body and fits into small blood vessels to lay eggs.

Eggs are able to burrow out of blood vessel into intestine lumen. Many eggs are laid to ensure the survival of the parasite. Large numbers of cercariae are released by snail. The miracidia and cercariae larvae have glands that secrete lytic enzymes which soften the tissue to allow for penetration into host. The male has a gynecophoric canal that carries the female to ensure that eggs are fertilised before being shed.

Has suckers for attachment. Prevention and Control Drain all stagnant water Boil drinking water. Do not wade bare feet in water. Wear long rubber boots and gloves for those who work in rice fields. Eliminate snails, by spraying with molluscides. Reporting to doctor early when symptoms appear for early treatment. Practical Activities Ecology is best studied outdoors.

Students identify a habitat within or near the school compound, e. The quadrat method is used. Observation and recording of the various animals as well as their feeding habits is done. Birds that feed on the plants or arthropods in the area studied are noted through observation of habitat at various times of the day. Food chains are constructed e. The numbers of animals in 1 m2 is counted directly or estimated e. The number of plants is easily counted and recorded and ratio of consumers to producers calculated.

It will be noted that in terms of numbers where invertebrates are involved, there are very many consumers of one plant. Several other quadrats are established and studied and averages calculated. Adaptions to Habitat Hydrophytes Specimen of hydrophytes e. Students should note the poorly developed root systems and broad leaves. Stomata distribution on leaf surface is studied through microscopy or by emersing a leaf in hot water and counting number of bubbles evolved.

Mesophytes Ordinary plants e. Size of leaves is noted and stomata distribution studied. Xerophytes Specimen include Euphorbia, cactus and sisal which are easily available. The root system e. It will be noted that sisal has fleshy leaves and stem while cactus and Euphorbia have fleshy stem but leaves are reduced to small hair-like structures. Comparison of Root nodules from fertile and poor soils Root nodules Are swellings on roots of leguminous plants.

Soil fertility determines number of root nodules per plant. Bean plants are best used in this study. One plot can be manured while the other is not. Similar seeds are planted in the two plots. The plants are uprooted when fully mature vegetatively i. The number of nodules per plant is counted. An average for each plot is calculated. It is noted that the beans from fertile soil have more and large nodules than those grown in poor soils.

Estimation of Population using Sampling Methods The number of organisms both producers and the various consumers is recorded in each area studied e. The total area of the habitat studied is measured. The average number of organisms per quadrat 1 m2 is calculated after establishing as many quadrats as are necessary to cover the area adequately. Total population of organisms is calculated from the area. Abiotic environment is studied within the area sampled.

Air temperature soil surface temperature are taken and recorded. This is best done at different times of day, i. Any variations are noted. Litmus papers can be used to indicate if soil is acidic or alkaline, but pH paper or meter gives more precise pH values. Humidity is measured using anhydrous blue cobalt chloride paper which gives a mere indication of level of humidity.

A windsock is used to give an indication of direction of wind. As all the abiotic factors are recorded observations are made to find the relationships between behaviour of organism and the environmental factors for example: The temperature affects the behaviour of animals.

The direction of wind will affect growth of plants. The level of humidity determines the type, number and distribution of organisms in an area. Reproduction in Plants and Animals Introduction The process by which mature individuals produce offspring is called reproduction.

Reproduction is a characteristic of all living organisms and prevents extinction of a species. There are two types of reproduction: sexual and asexual reproduction. Sexual reproduction involves the fusion of male and female gametes to form a zygote. Asexual reproduction does not involve gametes. Cell Division Cell division starts with division of nucleus. In the nucleus are a number of thread-like structures called chromosomes, which occur in pairs known as homologous chromosomes.

Each chromosome contains-genes that determine the characteristics of an organism. The cells in each organism contains a specific number of chromosomes. There are two types of cell division: Mitosis This takes place in all body cells of an organism to bring about increase in number of cells, resulting in growth and repair.

The number of chromosomes in daughter cells remain the same as that in the mother cell. Meiosis This type of cell division takes place in reproductive organs gonads to produce gametes. The number of chromosomes in the gamete is half that in the mother cell. Mitosis Mitosis is divided into four main stages.

Prophase, Metaphase, Anaphase and Telophase. These stages of cell division occur in a smooth and continuous pattern. Interphase The term interphase is used to describe the state of the nucleus when the cell is just about to divide. During this time the following take place: Replication of genetic material so that daughter cells will have the same number of chromosomes as the parent cell.

Division of cell organelles such as mitochondria, ribosomes and centrioles. Energy for cell division is synthesised and stored in form of Adenosine Triphosphate ATP to drive the cell through the entire process. Nuclear membrane and nucleolus are intact. Prophase The chromosomes shorten and thicken. Each chromosome is seen to consist of a pair of chromatids joined at a point called centromere. Centrioles in animal cells separate and move to opposite poles of the cell.

The centre of the nucleus is referred to as the equator. Spindle fibres begin to form, and connect the centriole pairs to the opposite poles. The nucleolus and nuclear membrane disintegrate and disappear. Metaphase Spindle fibres lengthen. In animal cells they attach to the centrioles at both poles. Each chromosome moves to the equatorial plane and is attached to the spindle fibres by the centromeres.

Chromatids begin to separate at the centromere. Anaphase Chromatids separate and migrate to the opposite poles due to the shortening of spindle fibres. Chromatids becomes a chromosome.

In animal cell, the cell membrane starts to constrict. Telophase The cell divides into two. In animal cells it occurs through cleavage of cell membrane. In plants cells, it is due to deposition of cellulose along the equator of the cell.

Cell plate formation. A nuclear membrane forms around each set of chromosome. Chromosomes later become less distinct. Significance of Mitosis It brings about the growth of an organism: It brings about asexual reproduction. Ensures that the chromosome number is retained. Ensures that the chromosomal constitution of the offspring is the same as the parents.

Meiosis Meiosis involves two divisions of the parental cell resulting into four daughter cells. The mother cell has the diploid number of chromosomes. The four cells gametes have half the number of chromosomes haploid that the mother cell had. In the first meiotic division there is a reduction in the chromosome number because homologous chromosomes and not chromatids separate. Each division has four stages Prophase, Metaphase, Anaphase and Telophase.

Interphase As in mitosis the cell prepares for division. This involves replication of chromosomes, organelles and build up of energy to be used during the meiotic division. First Meiotic division Prophase I Homologous chromosomes lie side by side in the process of synapsis forming pairs called bivalents.

Chromosomes shorten and thicken hence become more visible. Chromosomes may become coiled around each other and the chromatids may remain in contact at points called chiasmata singular chiasma.

Chromatids cross-over at the chiasmata exchanging chromatid portions. Important genetic changes usually result. Metaphase I Spindle fibres are fully formed and attached to the centromeres. The bivalents move to the equator of the spindles. Anaphase I Homologous chromosomes separate and migrate to opposite poles. This is brought about by shortening of spindle fibres hence pulling the chromosomes.

The number of chromosomes at each pole is half the number in the mother cell. Telophase I Cytoplasm divides to separate the two daughter cells. Second Meiotic Division Usually the two daughter cells go into a short resting stage interphase but sometimes the chromosomes remain condensed and the daughter cells go straight into metaphase of second meiotic division.

The second meiotic division takes place just like mitosis. Prophase II Each chromosome is seen as a pair of chromatids. Metaphase II Spindle forms and are attached to the chromatids at the centromeres.

Chromatids move to the equator. Anaphase II Sister chromatids separate from each other Then move to opposite poles, pulled by the shortening of the spindle fibres.

Telophase II The spindle apparatus disappears. The nucleolus reappears and nuclear membrane is formed around each set of chromatids.

The chromatids become chromosomes. Cytoplasm divides and four daughter cells are formed. Each has a haploid number of chromosomes. Significance of Meiosis Meiosis brings about formation of gametes that contain half the number of chromosomes as the parent cells. It helps to restore the diploid chromosomal constitution in a species at fertilisation. It brings about new gene combinations that lead to genetic variation in the offsprings. Asexual Reproduction Asexual reproduction is the formation of offspring from a single parent.

The offspring are identical to the parent. Types of asexual reproduction. Binary fission in amoeba. Spore formation in Rhizopus. Budding in yeast. Binary fission This involves the division of the parent organism into two daughter cells.

The nucleus first divides into two and then the cytoplasm separates into two portions Binary fission also occurs in bacteria, Paramecium, Trypanosoma and Euglena. Spore formation in Rhizopus Rhizopus is a saprophytic fungus which grows on various substrate such as bread, rotting fruits or other decaying organic matter. The vegetative body is called mycelium which has many branched threads called hyphae. Horizontal hyphae are called stolons.

Vertical hyphae are called sporangiophore. The tips of sporangiophore become swollen to form sporangia, the spore bearing structure. Each sporangium contains many spores. As it matures and ripens, it turns black in colour. When fully mature the sporangium wall burst and release spores which are dispersed by wind or insects. When spores land on moist substratum, they germinate and grow into a new Rhizopus and start another generation.

Spore formation in ferns The fern plant is called a sporophyte. On the lower side of the mature leaves are sari Singular: sorus which bear spores. Budding in Yeast Budding involves the formation of a protrusion called a bud from the body of the organism.

The bud separates from the parent cell, in yeast budding goes on so fast and the first bud starts to form another bud before the separation. A short chain or mass of cells is formed. Sexual Reproduction in Plants In flowering plants, the flower is the reproductive organ which is a specialised shoot consisting of a modified stem and leaves.

The stem-like part is the pedicel and receptacle, while modified leaves form corolla and calyx. Structure of a flower A typical flower consists of the following parts: Calyx made up of sepals. They enclose and protect the flower when it is in a bud. Some flowers have an outer whorl made of sepal-like structures called epicalyx. Corolla consists of petals.

The petals are brightly coloured in insect - pollinated flowers. Androecium Is the male part of the flower. It consists of stamens. Each stamen consists of a filament whose end has an anther. Inside the anther are pollen sacs which contain pollen grains. Gynoecium pistil Is the female part of the flower. It consists of one or more carpels. Each carpel consists of an ovary, a sty le and a stigma.

The ovary contains ovules which become seeds after fertilisation. A monocarpous pistil has one carpel e. A polycarpous pistil has many carpels. If the carpes are free, it is called apocarpous as in rose and Bryophyllum, In carpels that are fused it is called syncarpous as in Hibiscus.

A complete flower has all the four floral parts. A regular flower can be divided into two halves by any vertical section passing through the centre. Irregular flower can be divided into two halves in only one plane e. Pollination This is the transfer of pollen grains from the anther to the stigma.

Types of pollination Self pollination is the transfer of pollen grains from the anther of one flower to the stigma of the same flower. Cross-pollination is the transfer of pollen grains from the anther of one flower to the stigma of a different flower, of the same species. Agents of pollination Agents of pollination include wind, insects, birds and mammals. Insect pollinators include bees, butterflies and mosquitoes.

Mechanisms that hinder self-pollination Stamens ripen early and release their pollen grains before the stigma, mature.

This is called protandry e. The stigma matures earlier and dries before the anthers release the pollen grains. This is called protogyny and is common in grasses. Self sterility or incompatibility Pollen grains are sterile to the stigma of the same flower, e. Shorter stamens than pistils. Fertilisation in Plants The pollen grain contains the generative nucleus and a tube nucleus. When the pollen grain lands on the stigma, it absorbs nutrient and germinates forming a pollen tube.

This pollen tube grows through the style pushing its way between the cells. It gets nourishment from these cells. The tube nucleus occupies the position at the tip of the growing pollen tube. The generative nucleus follows behind the tube nucleus, and divides to form two male gamete nuclei. The pollen tube enters the ovule through the micropyle.

When the pollen tube penetrates the ovule disintegrates and the pollen tube bursts open leaving a clear way for the male nuclei. One male nucleus fuses with the egg cell nucleus to form a diploid zygote which develops into an embryo.

The other male gamete nucleus fuses with the polar nucleus to form a triploid nucleus which forms the primary endosperm. This is called double fertilisation. After fertilisation the following changes take place in a flower: The integuments develops into seed coat testa.

The zygote develops into an embryo. The triploid nucleus develops into an endosperm. The ovules become seeds. The ovary develops into a fruit. The ovary wall develops into pericarp.

The style, dries up and falls off leaving a scar. The corolla, calyx and stamens dry up and fall off. In some the calyx persists. Fruit formation Fruit development without fertilisation is called parthenocarpy e.

Such fruits do not have seeds. Classification of fruits False fruits develops from other parts such as calyx, corolla and receptacle, e. True fruits develop from the ovary, e. True fruits can be divided into fleshy or succulent fruits e. The dry ones can be divided into Dehiscent which split open to release seeds and indehiscent which do not open. Types of fruits Placentation This is the arrangement of the ovules in an ovary.

Marginal placentation: The placenta appears as one ridge on the ovary wall e. Parietal placentation: The placenta is on the ridges on ovary wall. Ovules are in them e. Axile placentation: The placenta is in the centre. Ovary is divided into a number of loculi. Basal placentation. The placenta is formed at the base of the ovary e. Free Central placentation. Placenta is in the centre of the ovary. Practicing mental calculation will strengthen your foundation for learning more advanced maths As opposed to using a calculator or pencil and paper, mental math is performed entirely in one's head.

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