WAEC Biology 2010 Theory Past Questions

Model answer

(i) Aerobic respiration: C6H12O6 + 6O2 -> 6CO2 + 6H2O + Energy. (ii) Anaerobic respiration in plants: C6H12O6 -> 2CO2 + 2C2H5OH + Energy. (iii) Anaerobic respiration in animals: C6H12O6 -> 2CH3CH(OH)COOH + Energy (lactic acid).

Model answer

The liver of a patient suffering from cancer of the liver will not be able to: regulate blood sugar, carry out detoxification, regulate lipid metabolism, and store iron (any four).

Model answer

A flame cell (protonephridium) diagram should show: the nucleus, blind end, flagella (the beating flagella create the flow used in excretion), the lumen, and the tubule leading away from the cell. (Note: the source PDF for this diagram was not accessible for image extraction; only the textual description is provided.)

Model answer

(i) Ripening of fruits - Ethylene. (ii) Breaking of dormancy - Gibberellins. (iii) Weed control - Auxin. (iv) Leaf fall - Abscisic acid.

Model answer

Hypogeal germination, e.g. maize; Epigeal germination, e.g. beans.

Model answer

Aim: To demonstrate the conditions necessary for germination. Method: Four beakers are labelled A, B, C and D, each containing a piece of cotton wool with dry bean seeds placed on it. In A, the seeds and cotton wool are left dry (no water added). In B, the cotton wool is moistened with water, but the beaker is kept in a refrigerator (cold, to exclude warmth). In C, the cotton wool is moistened and the beaker is placed on top of dissolved water so the seeds are submerged (excluding oxygen). In D, the cotton wool is moistened, warmth is maintained, and air/oxygen is freely available. Observation: The seeds in beakers A, B and C do not germinate because water, warmth, or oxygen (respectively) is missing, while the seeds in beaker D, where all three conditions are met, do germinate. Conclusion: Water, warmth and oxygen are all necessary for germination; if any one of them is missing, germination will not occur.

Model answer

Epiphytes grow on other plants purely for physical support - they are capable of photosynthesis and do not absorb manufactured food from the host plant. Parasites, by contrast, live in or on a host and absorb nutrients (manufactured food) directly from the host, harming it. Parasites that live outside the host are called ectoparasites, while those that live inside are called endoparasites.

Model answer

Examples of parasitic plants include mistletoe and dodder.

Model answer

(i) Population density is defined as the number of individuals of a species per unit area of the habitat: Population density = Population size / Area of habitat. (ii) Abiotic components (such as temperature, light, water, and soil) influence which organisms (biotic components) can survive in an environment, while the biotic components in turn affect the abiotic conditions - for example through respiration, decomposition and modification of soil and microclimate. Together, they interact continuously to shape the structure and function of the ecosystem.

Model answer

Characteristics that can be genetically transmitted in humans include: height, skin colour, body shape, and intelligence (any four).

Model answer

In plants, meiosis occurs in the anther and the ovary. In animals, meiosis occurs in the testes and the ovaries.

Model answer

Mitosis produces two daughter cells while meiosis produces four daughter cells. Mitosis occurs in somatic cells while meiosis occurs during the formation of gametes (in reproductive cells). Mitosis involves one division of the nucleus while meiosis involves two divisions. There is no exchange of genetic material during mitosis while meiosis involves crossing over/exchange of genetic material (any two).

Model answer

Homozygous 'A' (Mr. James) = AA. Heterozygous 'A' (mother) = AO. If Mr. James is AA (homozygous), he can only pass on the A allele to any child. Since blood group O requires the genotype OO (an O allele from each parent), and Mr. James has no O allele to give, he cannot be the father of a blood-group-O child. (i) The woman's claim is disproved. (ii) Mr. James, being homozygous AA, cannot pass on an O allele; a blood-group-O child (OO) requires an O allele from both biological parents, which is impossible in a cross with a homozygous-AA father.

Model answer

(i) Placentation refers to the formation and arrangement of the placenta in the uterus during pregnancy. (ii) Organs associated with the human placenta include the umbilical cord and the uterus (womb).

Model answer

Functions of the human placenta: (i) digested food is absorbed from the mother's blood and passed to the embryo; (ii) it selects what substances are to pass to the embryo's blood; (iii) it exchanges carbon dioxide from the embryo's blood for oxygen from the mother's blood; (iv) it produces hormones that support pregnancy; (v) it acts as a barrier against some harmful substances/pathogens (any five).

Model answer

(i) Viviparity: a mode of reproduction in which the young develop inside the mother's body and are born alive, as in most mammals. (ii) Territoriality: behaviour by which an organism defends a specific area (its territory) against intrusion by other individuals, often of the same species, in order to secure resources such as food, mates, or breeding sites. (iii) Seasonal migration: the periodic, often annual, movement of animals from one habitat to another and back, usually in response to changes in season, food availability, or breeding requirements.

Model answer

Adaptation refers to the features and/or behaviours that an organism possesses which enable it to live successfully in its habitat.

Model answer

(i) Succulent leaves in Aloe sp. are adapted for water storage/conservation. (ii) Succulent stems and reduced leaves in cactus plants reduce the rate of transpiration so that water is conserved. (iii) Short, strong beaks in fowls are adapted for picking insects, seeds, earthworms etc. (iv) Counter shading in fish helps in protection from predation (camouflage). (v) Scale leaves on needle-like branches of pine trees reduce the surface area for transpiration, helping conserve water.

Model answer

(i) Population is the total number of individuals of the same species living in a particular area at a particular time. (ii) Effects of overpopulation on a community: it increases competition for resources; it leads to food shortage; it may result in the spread of disease; it leads to crime; it encourages predation (any five).

Model answer

See the answers to 5(a) above - Part III offered a choice between this placenta-based question and the adaptation-based Question 8, of which candidates were required to answer only one.

Model answer

Adaptation refers to the features or behaviours that an organism possesses that enable it to live successfully in its habitat.

Model answer

(i) Succulent leaves in Aloe sp. are adapted for water conservation. (ii) Succulent stems and reduced leaves in cactus plants reduce the rate of transpiration so that water is conserved. (iii) Short, strong beaks in fowls are adapted for picking insects, seeds, earthworms etc. (iv) Counter shading in fish helps in protection from predation. (v) Scale leaves on needle-like branches of pine trees reduce the rate of transpiration.

Model answer

(i) Population is the total number of individuals of the same species living in a given area at a given time. (ii) Effects of overpopulation: increased competition, food shortage, spread of disease, increased crime, increased predation (any five).