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1.Explain how the various abiotic factors may affect plants

Temperature; affects soil formation and distribution of plants; affect transpiration rate as high temperatures lead to high rates of transpiration; It also affects the rate of photosynthesis with the direct influence on enzyme activity;

Light intensity; affects the rate of photosynthesis;

Wind; increase the transpiration rates; affects dispersal of seeds and fruits; agents of pollination; affect distribution in terms of wind storms/breakages;

Atmospheric pressure; high atmospheric pressure leads to low rates of transpiration; high oxygen and carbon (IV) oxide concentration; high photosynthetic rates; while low atmospheric pressure leads to high transpiration rates; less concentration of oxygen and carbon (IV) oxide; leading to low rates of photosynthesis;

Water/Rainfall; forms a raw material for photosynthesis; helps in support in plant tissues; affects distribution of plants; Humidity; low humidity leads to high transpiration rates; while high humidity leads to low rates of transpiration; pH; affects distribution of plants; some grow in acidic soils; others in alkaline soils; Edaphic/soil factors; affects plant distribution; in terms of being sources of water and mineral salts; provide a substratum for anchorage of plants;



2.Discuss the causes, effects and control measures for water pollution

Causes of water pollution are varied:

Industrial effluents; have heavy metals that poison aquatic organisms;

Untreated organic matter has phosphates/sulphates/nitrates/salts; that cause eutrophication; causing algal bloom that deprives the water of nutrients; when the algae die,they lead to an increase in putrefying bacteria whose decomposition activities lead to the release of awful smells/odours;

Oil effluents clog respiratory surfaces of aquatic organisms/death due to suffocation;

Domestic effluents/sewage; form a habitat of pathogens that spread water borne diseases; decomposing sewage promotes eutrophication leading to algal bloom; death promotes/attracts saprophytic bacteria that use up oxygen in water; causing suffocation/death to aquatic organisms;

Agrochemicals/fertilizers; phosphates/nitrates; cause eutrophication; heavy metals in agrochemicals (herbicides/pesticides); affect respiratory surfaces/cause breathing problems;

Hot water; raise temperature of water; killing organisms; dissolves less oxygen; reducing its content in water;

Oil spillage; in oceans from tanks/refineries; soak feathers of marine birds preventing flight; clogs respiratory surfaces leading to death; coats photosynthetic phytoplanktons; reduces light penetration hampering photosynthesis;

Sediments; from soil erosion makes water dirty; making it unfit for consumption; clogs respiratory surfaces hindering gaseous exchange; reduces light penetration hindering photosynthesis;

Control methods:

-Enforcement of environmental laws;

-Use of unleaded fuel/petroleum products;

-Proper treatment and disposal of sewage wastes;

-Treatment of industrial effluents before release;

-Public education on correct use of inorganic fertilizers and agrochemicals; and use of alternatives such as biological control of weeds/pests/organic manure;

-Use of undersea pipelines instead of tankers to transport oil products;

-Cooling hot water before release to water bodies;

3.How are xerophytes and hydrophytes adapted to their habitats

Xerophytes:

Thick waxy cuticle; minimize water loss;

Leaves are folded and reduced in size; to minimize stomatal transpiration;

Sunken stomata; to reduce rate of transpiration;

Thick/succulent leaves, side branches or stems; for water storage;

Shedding of leaves during the dry periods; to reduce surface area exposed for transpiration;

Reversed stomatal rhythm; prevent excessive loss of water;

Deep penetrating roots; to absorb water from deep below the surface;

Superficial roots; to absorb surface water run-off;

Leaves covered in scales/hairs; to trap a moist layer of air; to reduce the rate of transpiration;

Drought-resistant seeds; that remain dormant till favourable weather resumes;

Underground organs (corms/bulbs); for storage of water and reproduction;

Most stomata located on the lower leaf surface; to avoid exposure to direct light; to reduce evaporation;

Reduced number of stomata; to reduce the rate of transpiration;

Hydrophytes:

Stomata on the upper surface of leaves; to provide a large surface area for gaseous exchange; and loss of excess water;

Poorly-developed roots that lack root hairs; to reduce/avoid absorption of water;

Aerenchyma tissue in leaves, stems and roots; to store air; and for buoyancy;

Deeply-dissected leaves; to provide a large surface area for absorption of light;

Highly-sensitive; and numerous chloroplasts; for photosynthesis;

Greatly reduced vascular bundle; to avoid absorption of water;

Flowers raised above the water; to allow for pollination;

Lack of a cuticle or very thin cuticle; for faster loss of water;

4. Outline the differences between wind and insect pollinated flowers

-Flowers of wind pollinated plants are small; with no bracts, sepals or petals; if present the petals are small,inconspicuous; often white or green in colour; while insect pollinated flowers are large; often with brightlycoloured petals, bracts or inflorescence; to attract insects.

-Flowers of wind pollinated plants have no nectaries; and no scent; while flowers of insect pollinated plants are scented; and produce nectar;

-In wind pollinated flowers, the anthers are large; and loosely attached on a flexible filament; to allow pollengrains to be readily released when wind blows on the anthers; while anthers of insect pollinated flowers are usually small; and firmly attached on the filaments; this ensures that the insect rub against the anther; as they crawl into the flower collecting pollen grains onto their bodies;

-In wind pollinated flowers, the stigmas are feathery; widely spread; this acts as nets to catch pollen as it floats through the air; while in insect pollinated flowers the stigmas are small; smooth; and sticky; and are also enclosed; this feature ensures that pollen grains from the body of an insect stick onto it;

-In wind pollinated flowers, the flowers are simple with no particular shape; while some flowers that are insect pollinated have petals with grooves or dark lines; leading from the petal boarder to the nectaries; some have tubular or funnel-shaped corolla; and landing platforms; to guide the insect to the source of the nectar for their food;

-Flowers of wind pollinated plants are either on long stalks above the leaves; or develop from flower buds that open before the leaf buds; to increase the flower exposure to air currents; while flowers of insect pollinated plants are on short stalks; often enclosed by the corolla;

5.Describe what happens in a flower from the time of pollination up to thetime of seed and fruit development

After pollination, the pollen grain absorbs nutrients from the stigma; and develops a pollen tube; it grows down the style to the embryosac; taking along the male nuclei;

The tube nuclei initiates and maintains pollen tube growth; while the generative nucleus divides by mitosis;to form two male gamete nuclei; which follow behind the tube nucleus as the pollen tube grows down the style;pollen tube enters the ovule through the micropyle; its tip bursts open; while the tube nucleus disintegrates;one of the male gamete nucleus fuses with the egg cell nucleus/oosphere/megaspore; to form the zygote;while the other fuses with the two polar nuclei; to form a triploid nucleus; called the primary endospermnucleus;

After fertilization, the zygote undergoes repeated mitotic divisions; to form an embryo consisting of theplumule, radicle and seed leaves/cotyledons; primary endosperm nucleus divide repeatedly,become separated by membranes; to form an (semi-fluid nutritive) endosperm;

Ovary walls change into the pericarp; ovary changes/develops into a fruit; while ovules lose water and become seeds; the integuments; change into seed coats/testa; style/filaments/petals/sepals wither and fall off (or may persist);

6. Discuss the adaptations of the female reproductive system

Elastic uterine walls; to expand so as to accommodate the growing foetus;

Muscular foot of the pelvis and bladder support the weight of the growing foetus;

Funnel-shaped ends of the oviduct; direct the ova released to the uterus;

Muscular uterine walls; contract and relax to expel the foetus at birth;

Long vaginal canal; allow sufficient entry of penis to avoid wastage of sperms;

The two ovaries maximize chances of releasing ovum after every circle (28 days);

Ovaries are well vascularised/have good blood supply; to ensure nourishment of cells involved in oogenesis (primordial mother/germ cells) or egg formation;

High number of potential mother cells; ensures maximum number of ova which develop to maturity;

Plenty of yolk in egg cells; which nourish the foetus before the placenta becomes functional;

The vitelline membrane of the ovum thickens after fertilization; preventing further entry of sperms;

The oviduct wall is able to contract; in order to facilitate movement of ovum down the oviduct;

Has cilia to waft the ovum forward; wall of the vagina/vulva produce mucus; to lubricate the penis during copulation;

Clitoris; has many nerve endings; to provide maximum stimulation during copulation for maximum ejaculation and faster movement of spermatozoa;

7.Describe the process of gaseous exchange in terrestrial plants

Gaseous exchange occurs in the spongy mesophyll;

During the day, air diffuses into large air spaces of the spongy mesophyll; through the stomata; the carbon (IV) oxide in the air diffuses into photosynthetic cells; in solution form; during photosynthesis, carbon (IV) oxide is used up; while oxygen is produced; some of the oxygen is used in respiration; while the rest diffuses out of the leaf; through the stomata;

During the night, air diffuses into the air spaces; through the stomata; the air dissolves into the film of moisture;oxygen in the air diffuses into the cells; and is used for respiration; carbon (IV) oxide produced; diffuses out through stomata; due to a concentration gradient/diffusion gradient; At night, carbon (IV) oxide accumulates in the leaf since photosynthesis does not occur; some gaseous exchange also takes place through the cuticle; and through the epidermis of young leaves, roots and stems; some plants exchange gases through breathing roots/pneumatophores; older stems exchange gases through lenticels;



8. How is the mammalian gaseous exchange system adapted to its functions?

Nasal cavity; has cells that produce mucus; that together with hairs/cilia; trap and propel dust/microbes to the pharynx to be breathed out/swallowed;

Cavity is supplied with capillaries; that warm the air for faster flow in the channels;

Epiglottis; covers the trachea during swallowing; so that particles of food and water may not enter the trachea;

Trachea and bronchi; have cartilage rings; to keep the passages open/prevent them from collapsing; so that air moves in and out freely and continuously; are also lined with mucous membranes which have hairs/ciliated;whose movement/wafting push out dust particles collected in the passages into the pharynx; richly-supplied with blood vessels; to warm the air; for faster flow;

Lungs; have numerous alveoli; to increase the surface area for gaseous exchange;

Alveoli have a thin epithelium; to reduce the distance through which gases diffuse for easier and faster diffusion; alveoli are moist; to dissolve oxygen for faster transport;

Lungs are spongy; because of many air sacs that contain a large amount of/volume of air; Lungs are also supplied with many blood vessels; for transportation of gases; they are also supplied with a network system of trachea, bronchi and bronchioles; to provide an efficient system/large surface area for gaseous exchange;

Lungs are enclosed in a pleural membrane; which secrete pleural fluid; that protect the lung surface; lubricate the chest cavity; allowing smooth movement of lungs as they change volumes;

Ribs have intercostal muscles; that moves/contracts and relaxes to allow for inhalation and exhalation; ribs also protect the lungs; has the diaphragm muscles whose contraction and relaxation leads to inhalation and exhalation respectively;

9. Describe the role of the following hormones in the menstrual cycle

a. Luteinising Hormone (LH)

Produced by the pituitary gland; under the influence of oestrogen hormone; cause the bursting of the Graafian follicle; to release a mature egg/ovum/causes ovulation; stimulates the change/conversion of the Graafian follicle; into the corpus luteum; stimulates the corpus luteum; to secrete progesterone hormone;

b. Follicle Stimulating Hormone (FSH)

Produced by the anterior lobe of the pituitary gland; it stimulates the maturation of the Graafian follicle in the ovaries; stimulates the ovarian tissue/wall to secrete oestrogen;

c. Oestrogen

Brings about/stimulates the healing and repair of the uterine wall; after menstruation; stimulates the pituitary gland; to secrete luteinising hormone;

d. Progesterone

Secreted by the corpus luteum; it stimulates the thickening of the endometrium/uterine wall; in preparation for implantation; inhibits secretion of the Follicle Stimulating Hormone; therefore preventing further development of the Graafian follicle;



10 a. What is secondary growth?

Type of growth that occurs due to cambium activity in woody plants/stems; resulting in an increase in girth/width of plants;

b. Describe the process of secondary thickening in a woody stem

Facilitated by meristematic cells (cambium) located between the phloem and the xylem (intervascular cambium); it divides radially to form cambium tissues; with xylem forming the outer ring/to the inside;while the phloem forming the outer ring/to the outside; division of the cambium ring; form a secondary parenchyma; hence increases/forms the medullary rays; other xylems (secondary xylem) are formed;hence pushes the phloem and cambium ring outwards; this creates pressure on the outer cells;resulting in stretching and eventual rupturing of epidermal cells;

A new band/volume of cambium cells are formed in the cortex beneath the epidermis (cork cambium cells/phellogen); to replace these ruptured cells; the phellogen cells divide on either side; where the inner cells become the secondary cortex; while those produced on the outside become cork cells;which are tightly packed; and become coated with an oily/waxy water-proof material/suberin;

Further multiplication of cork cells; lead to formation of the bark; which forms a protective layer (against water loss and damage by organisms); seasons results into annual rings; some cork cells form a loose mass/lenticels that allow gaseous exchange through the stem;



11. Discuss the role of the various hormones in plant growth and development

Indole Acetic Acid/Auxins;

Influences/promotes cell division/elongation (in cambium causing secondary thickening); induces tropisms;promotes fruit formation/parthenocarpy; promotes formation of abscission layer/leaf fall; promotes cell differentiation (of vascular tissue); causes apical dominance/inhibits lateral bud formation; promotes growth of adventitious roots; in conjunction with cytokinins, it induces callous tissue formation;

Gibberellins/Gibberellic acid;

Promotes cell division/elongation in dwarf plants; promotes parthenocarpy; setting of fruit after fertilization initiating formation of fruits; formation of side branches of stems/ends apical bud dormancy; inhibits adventitious root growth; activates hydrolytic enzymes in germination/promotes germination of seeds/breaks seed dormancy; affects leaf expansion and shape/retards leaf abscission;

Cytokinins (e.g. Zeatin or Kinetin);

Promotes flowering in some plant species; breaks dormancy in some plant species; promotes cell division in presence of auxins; stabilizes protein and chlorophyll; promotes root formation on a shoot; low concentration encourages leaf senescence/increases cell enlargement in leaves; stimulates lateral bud formation;

Ethylene/Ethene;

Promotes ripening of fruits; induces thickening of stem/inhibits stem elongation; promotes flower morphogenesis/formation or flowering in pineapples; causes abscission of leaves/fruit/leaf fall;

Abscissic acid;

High concentration causes stomatal closure; inhibits stem elongation/growth; inhibits sprouting of buds/induces bud dormancy; inhibits seed germination/growth/causes/promotes seed dormancy; causes abscission of leaves/fruits/leaf fall;

Traumatin;

Heals wounds by promoting callous formation;

Florigen;

Promotes flowering;

12. Discuss the adaptations of the male reproductive system of humans

Consists of two oval-shaped testes; lying outside the abdominal cavity in a special sac known as the scrotal sac/scrotum; for protection; the testes are located outside the body to provide a relatively cooler environment/lower temperature; suitable for sperm production; the inside of the testis is divided into seminiferous tubules;there are three coiled and twisted tubules; having rapidly/actively dividing cells that produce sperms;

Interstitial cells; found between these tubules produce the male sex hormones/androgens (mainly testosterone); important in promoting the development of secondary sexual characteristics; and maintaining masculinity in males; the tubules join together to form the epididymis; which are smaller ducts; that convey sperms out of the testes; they also form a temporary storage area for sperms; the epididymis is connected to the sperm duct/vas deferens; which has thick muscular walls; that contracts to propel sperms to the urethra; the sperm duct is joined by a duct from the seminal vesicle; a blindly ending sac; that produces an alkaline fluid containing nutrients for the spermatozoa/sperm cells; to provide energy; at the junction of the two sperm ducts (one from each testis) and urinary bladder there is the prostate gland; that secretes an alkaline fluid that neutralizes the acidic vaginal fluids; and also activates the sperms; by addition ofenzymes and diluting the sperms; below the prostate gland is the cowper’s gland; which secretes an alkaline fluid which neutralizes the acidity caused by urine; along the urethra.

The urethra; is a long tube running the length of the penis; used for conduction and expulsion of urine; as well as passage of sperms during copulation; the urethra follows the penis; that projects from the body at the lower abdomen; it consists of a retractable skin known as the prepuce/foreskin; that covers a swollen/bulbous end region of the penis known as the glans; the glands excites the clitoris of the female as it brushes on it during copulation; to stimulate ejaculation/orgasm; the penis is made up of spongy erectile tissue; consisting ofnumerous small blood spaces, muscle and blood vessels; the spongy tissue gets filled with blood; making the penis to become erect during sexual stimulation excitement and activity; enabling the penis to penetrate the vagina during coitus/copulation/sexual intercourse; in order to deposit sperms in the vagina of the female;

13. State the economic importance of members of Monera and Fungi and for each economic importance name a suitable or appropriate organism

Fungi:

-Yeast is used in the production of alcohol; and raising dough in baking; production of vitamins B2 and B12 and for beer brewing;

-Some mushrooms are used as food; Saprophytic fungi such as Mucor spp/Rhizopus spp cause food spoilage;are also used in retting of natural fibres such as flax; and in the curing of tea and tobacco;

-The fungi also decompose organic matter helping to clean the environment and recycle materials.

-Saprophytic fungi are also used to make silage; compost; and digesting sewage in sewage treatment plants;

-Penicillium spp is used for the manufacture of antibiotics;

-Fungi is used for making ghee and cheese in dairies;

-Parasitic fungi such as Phytophthora spp infest crops e.g. potatoes and tomatoes and destroy them/cause blight;

-Some fungi such as Aspergillus spp produce food poisons and is also used in the synthesis of enzyme amylase;

-Mycorrizae fungi enable trees e.g. pinus to absorb water and mineral salts more efficiently in silviculture/manmade forests;

-Some fungi such as and Tinus spp cause diseases such as yeast infections (Candidiasis;Athlete foot;) and;ringworms; respectively;

-Candida spp is used in making enriched food/single-celled proteins used in animal feeds/silage;

-Gibberella spp is used in the synthesis of Gibberellins for plant growth; it also causes poor crop growth through bolting of plants e.g. rice and wheat;

Bacteria:

-Some bacteria e.g. Vibrio spp cause disease to humans and other animals (any one disease);

-Clostridium spp and Bacillus spp bacteria are used in retting of flax;

-Lactobacillus spp are important in the manufacture of yoghurt/silage; and lactic acid;

-Some bacteria e.g. Streptomyces are used in making antibiotics (Streptomycin);

-Organic acids such as acetic and ethanoic acids are made using Acetobacter spp of bacteria;

-Some bacteria like the soil bacteria (Bacillus spp) make enzymes used in detergents;

-Escherichia coli (E. coli)/colon bacteria contaminates drinking water and may cause diseases;

-Bacteria such as Bacillus spp and are used in making hormones such as insulin through genetic engineering/modification;

-All saprophytic bacteria such as E. coli/Bacillus spp/Pseudomonas spp are used in the production of methane/biogas;

-Rhizobium spp of bacteria helps in nitrogen fixation making soils fertile;