Biology Past Questions | JAMB, WAEC, NECO and Post UTME Past Questions

The father's sperm contains about half X and half Y chromosomes. The sperm are the variable factor in determining the sex of the baby. If the sperm carries an X chromosome, it will combine with the egg's X chromosome to form a female zygote. If the sperm carries a Y chromosome, it will result in a male.

Leguminous plants are grown alternately with non-leguminous plants to restore the fertility of the soil. Legumes have bacteria on nodules which are on the roots of the plant. The bacteria on the nodules takes nitrogen from the air and fixes it into the soil, so that other plants that require nitrogen can use it as well. This nitrogen cycle is used in what farmers call a crop rotation.

Lightning discharges are a major source of nitrogen oxide gases. The two primary gases, nitrogen(II) oxide and nitrogen(IV) oxide are formed during the lightning discharge when the air is heated to 30,000 degrees inside the lightning channel.

Since air is made up of approximately 80% nitrogen and 20% oxygen, these molecules breakup into nitrogen and oxygen atoms. When the channel expands outwards and cools, new compounds form as a result of the nitrogen and oxygen atoms recombining. The amount of nitrogen oxide gases formed is related to the rate of cooling of the channel.

Humus refers to the fraction of soil organic matter that is amorphous and without the cellular cake structure characteristic of plants, micro-organisms or animals. It is the dark organic matter that forms in the soil when plant and animal matter decays and it contains many useful nutrients for healthy soil, nitrogen being the most important of all. The experiment in the question above was used to determine the presence of humus in the dried soil.

When we breathe in, air moves from our nostril to our trachea and bronchus and then to the bronchiole. Oxygen from the air then enters small air sacs, called alveoli, in the lungs. Oxygen diffuses from there into the bloodstream.

Syphilis and gonorrhoea are common sexually transmitted diseases caused by bacteria. Tuberculosis is also caused by bacteria that most often affect the lungs but smallpox, polio and measles are caused by viruses. Sleeping sickness on the other hand is caused by protozoa.

Adult anopheles mosquitoes lay 50 to 200 eggs per oviposition. The eggs are quite small (about 0.5 × 0.2 mm). Eggs are laid singly and directly on water. They are unique in that they have floats on either side. Eggs are not resistant to drying and hatch within 2 to 3 days, although hatching may take up to 2 to 3 weeks in colder climates.

Transpiration is the loss of water by evaporation from the leaves through the stomata. A weight potometer measures the amount of water lost by a plant. However, the amount of water loss from a leaf can be detected using blue cobalt chloride paper.

Cilia is a tiny hairlike projection on the surface of some cells and microscopic organisms, especially protozoans. Cilia are capable of whipping motions and are used by some microorganisms, such as paramecia, for movement.

A flagellum is a whip-like structure that allows a cell to move. They are found in all three domains of the living world: bacteria, archaea, and eukaryota, also known as protists, plants, animals, and fungi.

Amoebas use pseudopodia to move through their habitat and consume food. A chaetae on the other hand, is a chitinous bristle or seta found on an insect, arthropod or annelid worms such as the earthworm used in locomotion.

When pollen is transported by wind, this is called wind pollination. Wind-pollinated plants do not invest in resources that attract pollinating organisms, such as showy flowers, nectar, and scent. Instead, they produce larger quantities of light, dry pollen from small, plain flowers that can be carried on the wind.

Flowers that are wind-pollinated usually have a large amount of pollen produced with light smooth pollen grains. Also, the flowers are small and inconspicous with large pendulous anther. As mentioned above, they do not have scented petals needed to attract pollinating organisms.