2017 - JAMB Biology Past Questions and Answers - page 1

Most enzymes do not function optimally, or even at all, unless bound to other non-protein helper molecules called cofactors.

Wind vane is used to measure the direction of the wind.

Eye coloration is a caused by morphological variation

It consists of a lipid bi-layer with embedded proteins. The basic function of the cell membrane is to protect the cell from its surroundings.

The cell membrane controls the movement of substances in and out of cells and organelles. In this way, it is selectively permeable to ions and organic molecules

Feeding relationships between organisms in a community are represented by food chains, which show the sequence in which organisms feed on each other. The chain generally begins with an autotroph such as a green plant (e.g. stinging nettle ---> small tortoiseshell butterfly caterpillar --> house sparrow --> sparrowhawk), or with dead organic matter (detritus) (e.g. leaf litter --> earthworm --> young blackbird --> fox). The arrows indicate the passage of food, and therefore energy flow, from one organism to another.

Pyramids of energy are the most accurate representation of feeding relationships in a community, providing information about the amount of energy flowing through each trophic level over a set period of time.

Food web involve many complex feeding relationship and most most ecosystems are more complex than food chain

Nitrogen is essential to all living systems, which makes the nitrogen cycle one of Earth's most important nutrient cycles.

Atmospheric nitrogen becomes part of living organisms in two ways. The first is through bacteria in the soil that form nitrates out of nitrogen in the air. The second is through lightning. During electrical storms, large amounts of nitrogen are oxidized and united with water to produce an acid that falls to Earth in rainfall and deposits nitrates in the soil.

Morphological variation includes aspects of the outward appearance i.e shape, structure, color, pattern, size which is in contrast to physiology variation which deals primarily with function.

Morphological variation arises from a number of factors which can be bluntly classified as either genetic or environmental implanted into the process of evolution.

Discontinuous variation is variation that has distinct groups for organisms to belong to i.e tongue rolling, finger prints, eye color, blood groups

spirogyra and volvox are cells

Cohesion is an ability of water molecule to stick to one another due to the presence of hydrogen bonding

Nucleus is a specialized structure occurring in most cells (except bacteria and blue-green algae) and separated from the rest of the cell by a double layer, the nuclear membrane. This membrane seems to be continuous with the endoplasmic reticulum (a membranous network) of the cell and has pores, which probably permit the entrance of large molecules. The nucleus controls and regulates the activities of the cell (e.g., growth and metabolism) and carries the genes, structures that contain the hereditary information.