JAMB Biology 1989

C: 4

Label 4 points to a mitochondrion, recognisable by its internal folded membrane. Mitochondria produce much of a typical aerobic cell’s ATP through oxidative phosphorylation, hence the familiar powerhouse description.

A: angiosperms

In angiosperms, one sperm fertilises the egg while another fuses with the central cell to initiate endosperm development. This embryo-plus-endosperm outcome is the characteristic double fertilisation of flowering plants.

C: diffusion and active transport

Mineral ions can enter root cells passively down suitable electrochemical gradients or by transport requiring metabolic energy. Osmosis specifically describes water movement, and imbibition is water uptake by materials.

B: Possession of two pairs of antennae

Typical crustaceans possess two pairs of antennae: antennules and antennae. Their appendages are specialised rather than all serving as walking legs, and walking-leg counts differ among crustacean groups.

D: visceral mass and foot

A snail has a head, a muscular foot and a visceral mass containing many internal organs. These are molluscan body regions; thorax and abdomen are not the corresponding three-part division for a snail.

C: sieve tube

Companion cells are closely associated with sieve-tube elements in angiosperm phloem. They help maintain the living transport cells and participate in loading or unloading sugars for translocation.

A: the rate of respiration may equal that of photosynthesis

At the light compensation point, photosynthetic carbon uptake balances carbon dioxide release by respiration. Respiration continues in dim light, so low illumination does not stop it or necessarily increase oxygen output.

C: steapsin and trypsinogen

Pancreatic juice contains pancreatic amylase (amylopsin), pancreatic lipase (steapsin) and trypsinogen. Trypsinogen is an inactive enzyme precursor that is activated in the small intestine, limiting digestion of pancreatic tissue.

B: liver

Macrophages in the liver help remove old red blood cells and recycle their components. The spleen and bone marrow also participate, so the liver is one removal site rather than the only one.

B: Group A serum mixes with Group B erythrocytes

Group A serum normally contains anti-B antibodies. These bind B antigens on group B erythrocytes and cross-link the cells, causing agglutination. Matching group A or B combinations do not have that ABO incompatibility.

D: hinge joint

Label 5 marks the elbow articulation between the upper-arm bone and the forearm. Its main movement is flexion and extension in one plane, characteristic of a hinge joint. Rotation of the forearm involves a separate pivot articulation.

C: growth

Growth is an irreversible increase in an organism’s size or mass through addition of living material. Anabolism builds molecules that contribute to growth, while development includes changes in form and differentiation.

D: auxin, cytokinin and gibberellin

Auxins, cytokinins and gibberellins can promote cell expansion, cell division and fruit growth. The response depends on the plant and developmental stage; these hormones are not interchangeable with ripening or stress signals.

D: medulla oblongata

The medulla oblongata contains centres involved in automatic breathing and cardiovascular regulation. These vital functions continue without conscious commands, although other brain regions can influence them.

C: centromere

The two sister chromatids of a duplicated chromosome are joined at the centromere region. During division, spindle microtubules attach at kinetochores assembled there and help separate the chromatids.

C: homozygous

An organism is homozygous at a locus when its two alleles are the same, such as AA or aa. Different alleles, such as Aa, make it heterozygous; this describes genotype rather than mating behaviour.

D: Inherited red–green colour-vision deficiency

Common inherited red–green colour-vision deficiency is usually X-linked. Its inheritance is therefore associated with a sex chromosome, unlike sickle-cell anaemia, which is associated with an autosomal gene.

B: a symbiotic association

A lichen is an association of a fungus with a photosynthetic partner, typically a green alga or cyanobacterium. The partners live together in an organised structure rather than forming a single flowering or carnivorous plant.

D: syphilis

Syphilis is caused by the bacterium Treponema pallidum. Ringworm is a fungal infection, poliomyelitis is caused by poliovirus and malaria is caused by Plasmodium parasites.

C: 4.0 g per 100 g dry soil

The mass lost is 5.0 − 4.8 = 0.2 g. Relative to the initial 5.0 g of dry soil, this is (0.2 ÷ 5.0) × 100 = 4.0 g per 100 g. This estimate assumes that the mass loss represents the organic fraction being measured.

B: increase in salinity

Irrigation water contains dissolved salts. When water evaporates or is taken up by crops and drainage does not remove enough salts, they accumulate in the root zone and can reduce crop growth.