(a) Explain briefly the following types of fertilization in animals; (i) external fertilization (ii) internal fertilization (b) Name two groups of animal each that exhibit the types of fertilization in (a) (c)(i) If the placenta in a pregnant woman is detached from the uterine wall, give three effect this will have on the foetus (ii) Name three other features in the uterus of a pregnant woman that are useful for the development of the foetus (d) Explain briefly how the activities of organisms bring bout dynamic equilibrium in the habitat. (e) State four problems that organisms in the intertidal zone of a marine habitat could encounter. (f) Explain briefly the reasons that the following factors are necessary for germination; (i) moisture (ii) viable seeds (g) Explain briefly the reason light energy is considered a limiting factor in the production of foods by autotrophs.
Explanation
(a)(i) External Fertilization; Involves the release of eggs by the female to the outside environment where a male sheds its sperms on them for fertilization outside the body of the female. (ii) Internal Fertilization; Involves the release of eggs inside the body of a female males deposit sperms inside the female where fertilization occurs. (b)(i) Groups of Animal that exhibit external fertilization ;- Fish/pisces, amphibians (ii) Groups of Animal that exhibit internal fertilization;- Reptiles, birds/aves, mammals (c)(i) Effect of Detached Placenta on a Foetus; The exchange of dissolved food substances/oxygen/antibodies between a foetus and the mother will cease, removal of waste products from foetus will cease production of progesterone/hormone will cease might lead to the death of foetus/miscarriage/abortion/still birth. Certain molecules may pass into the body of foetus. (ii) Other Features Present in the Uterus of a Pregnant Woman; Umbilical cord, amnion, amniotic fluid, allantois, Chorion (d) Dynamic Equilibrium; Nature does not encourage any population exceeding the carrying capacity of the habitat, living organisms play a role in the regulation of the abundance of organisms/population in the habitat. Interaction among various populations lead to competition which may result in the elimination of one species or its restriction to a non-competitive position, Plants sometimes compete by producing toxic chemicals that inhibit neighboring species, there also exists predator-prey relationship/association between animals all these forces act together to achieve dynamic equilibrium in the habitat. (e) Problem that Organisms in Intertidal Zones of Marine Habitats could Encounter; Tendency of being carried away by waves drying up/desiccation/exposure to air, varied osmotic balance oxygen deficiency, low light intensity for producers, reduced visibility in animals, fluctuation of water temperature.. (f) Reasons the following factors are necessary for germination; (i) Moisture;- A seed imbibes/absorbs moisture causing the seed to swell and the testa becomes more permeable to oxygen and carbon (IV) oxide. This swelling will rupture the testa before germination starts, the moisture/water activates the enzymes for metabolism leading to germination (ii) Viable Seed;- Has a living/healthy embryo, intact healthy cotyledon/endosperm, whole without boring from insect. (g) Reason Light energy is Considered a Limited Factor in the Production of Food by Autotrophs; Light energy is obtained from the sun which is an important factor for photosynthesis/photolysis of water that is a process of manufacturing/producing food by autotrophs at optimum temperature/sunlight/solar/light energy green plants/autotrophs will manufacture food.
