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Parasitism Mutualism Commensalism Tapeworm in the gut of humans Mistletoe and Cacao plant Lichen Cattle and white Egret Flowers and Honeybees Remora and shark b. (i) Adaptive features of parasites - possession of specialised organs/haustoria/suckers/hooks; for attachment to the surface of the body of the host; - specialised piercing/sucking mouthparts; for sucking fluids/blood/plant juices; - hermaphrodite/ability to reproduce rapidly/easily in large numbers/large quantity of eggs are produced; to propagate their lineage/species; - large surface area; for absorption of digested food; - possession of special features/structures/cuticle; to withstand harsh environment/conditions/being digested. (ii) Effects of parasites on their host Absorption of nutrients from the body of the host can: - lead to stunted growth; - lead to low resistance to diseases in the host; - lead to loss of blood; - lead to loss of weight; - lead to septicaemia; - cause diseases/injuries/harm; - lead to death; - de-value the worth of animal skin/hides/ reduce the value of farm animals. c. (i) Saprophytes are organisms that feed; on dead/decaying/decomposing organic matter. (ii) Examples of saprophytes - Fungi/Bacteria/ - Mushroom - Azotobacter - Rhizopus; - Clostridium - Mucor - Streptomycetes - Toadstool - Mold/mould - Penicillium - Saccharomyces - Aspergillus - Yeast.

(ii) Phenotypic ratio 2:2 or 1:1/Ratio of sickler to non-sicklers. b. Reasons why a rhesus negative woman married to a rhesus positive man might lose her second pregnancy - Rhesus negative mother has no antigen on the surface of her Red Blood Cells/RBC; - the husband has antigen on his RBC; - during her first pregnancy, the child carries positive Rhesus factor; - the Rhesus factor enters the mother’s blood stream; - due to rupture of the placenta, blood seeps into the mother's blood; - causing it to develop anti-Rhesus antibodies; - causing agglutination in small proportion of foetal blood cells; - in the second pregnancy, the child might be Rhesus positive; - the child carrying Rhesus positive suffers massive destruction of red blood cells/erythroblastosis fetalis; - which might result into miscarriage of the second child. c. Examples of features in animals that support the theory of use and disuse of body parts as used by Lamarck - long neck in Giraffe; - smaller wings in Penguins; - lost legs of snakes; - long legs of Heron; - webbed feet of ducks/frogs/geese. d. Vestigial organs in mammals - appendix in humans; - pelvic and leg bones in whale; - reduced coccyx in man/caudal vertebrae; - pyramidalis nasi (extrinsic) muscle/muscles of the forehead; - posterior auricular muscles to move the ear/pinna; - erector muscle; - nipples in males; - sinuses; - tonsils; - wisdom teeth; - hairs on the chest.

a. Importance of the following in the Nitrogen Cycle (i) Lightning - When lightning occurs, nitrogen reacts with oxygen in air to form nitrous oxide/oxides of nitrogen; - which is further oxidised to form nitrogen (IV) oxide /nitrogen dioxide; - which dissolves in rain water to form nitric and nitrous acids; - (that fall to the ground) when it reaches the soil combines with bases/mineral salts to form nitrates; - which the plants absorbs. (ii) Nitrosomonas - Is a nitrifying bacterium in the soil; - that converts ammonia to nitrites in the soil. (iii) Azotobacter - Is a nitrogen-fixing bacterium in the soil; - that converts nitrogen in the soil; - into ammonium compounds/amino compounds and protein in the soil; - converts nitrites to nitrates in the soil. b. Excretory organs Insects – malpighian tubules; Earthworm – nephridium c. Explanation of diseases (i) Hepatitis - Is the inflammation/destruction of liver cells; - hepatitis can arise from bacteria/virus/an autoimmune disease; - or from excess consumption of alcohol. The symptoms include fatigue; - loss of appetite/anorexia; - muscle aches/pains; - flu; - fever; - nausea; - jaundice; - and dark coloured urine/stool. (ii) Kidney stones - Are small solids/crystals of concentrated minerals/uric acid found in the urine; - they are formed if there is an excessive loss of water/insufficient water intake; - so that the solubility of minerals/calcium phosphate/calcium oxalate in the urine is reduced; - high levels of uric acids/amino acids can lead to kidney stones; - bacteria may be trapped in the kidney tubules as the kidney stones get bigger; - symptoms are sharp pain at the flank of back; - frequent urination; - nausea; - sweating; - kidney stones can be treated by medications; - change in diet of food rich in calcium; - surgery; - drinking plenty of water. d. (i) Effects of lack of sense receptors in the skin - Humans will not be able to sense/feel/perceive external stimuli in the environment; - pain; - touch; - a change in temperature; - pressure; - danger which could lead to death. (ii) Layers of the epidermis - cornified layer/stratum corneum; - granular layer/stratum granulosum; - malpighian layer/stratum Malpighi. e. (i) Metamorphosis Is the development of some/certain organisms from the egg; to an adult stage; involving three to four stages. (ii) Type of metamorphosis of listed insects Insect Type of metamorphosis Grasshopper Incomplete Cockroach Incomplete Butterfly Complete Mosquito Complete Housefly Complete

a. Table Organism Mode of feeding Feature of mouthpart that adapts organism to mode of feeding Adult mosquito Fluid feeding/piercing/sucking Proboscis/modified long mandible and maxillae Weevil Chewing/boring Possession of pointed short and strong rostrum Cockroach Biting/chewing Well developed mandibles/strong sharp mandibles b. Parts of alimentary canal of earthworm - Mouth; - Pharynx; - Oesophagus/gullet; - Crop; - Gizzard - Intestine; - Anus. c. Ways by which water could be polluted by agricultural practices - Farmers add excess fertilizers/organic material to soil which may cause water pollution; - The inorganic/artificial fertilizers that contain high concentrations of nitrates and phosphates, dissolves in rain water and washed into nearby streams and rivers; - Nitrates and phosphates accelerate the growth of algae/eutrophication; - The death/decay of algae in rivers and streams increase the population of bacteria rapidly; - And cause oxygen level to decrease drastically; - Killing aquatic organisms; - Use of chemicals/dynamite for fishing which pollutes water - Dumping of cleared vegetation on water bodies; - Slash-burn methods of farming which might wash ash to nearby rivers/water bodies; - Pesticides/insecticides also sprayed on crops are usually non-biodegradable; - They are washed into nearby rivers/streams/water bodies; - Accumulate in the bodies of aquatic organisms; - And are passed along the food chain; - The concentration of pesticides/insecticides can reach toxic level in the bodies of the final consumers in the higher trophic levels is causing these organisms to die; d. (i) Life cycle of a Housefly - The female housefly lays eggs on decomposing matter/rubbish; - The eggs hatch into larvae/maggot; - In a few hours; - They crawl unto food; - Which if solid will be digested by enzymes to liquid; - The larvae have twelve segments on the body; - The body then contracts; - The skin hardens and turns brown to enclose the pupa; - After about four days, the pupa changes into the adult/imago; - Inside the puparium/brown skin cover; - The adult fly then emerges; - And flies away. OR e. Diagram of a mature maize seedling

No expanded working has been attached for this question yet. The verified answer is Option C.

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No expanded working has been attached for this question yet. The verified answer is Option A.

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The diagram represents the cell division process. The part labelled I is the Centriole. See the labelled diagram above.

Difference in concentration affects the rate of diffusion. The greater the concentration gradient, the quicker diffusion takes place.

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No expanded working has been attached for this question yet. The verified answer is Option C.

No expanded working has been attached for this question yet. The verified answer is Option C.

No expanded working has been attached for this question yet. The verified answer is Option C.