JAMB Biology 2008 Past Questions & Answers

The system for classifying organisms is a hierarchy, arranged from the smallest group to the largest: Species, Genus, Family, Order, Class, Phylum, Kingdom. A more inclusive taxon is a larger group that contains more of the smaller groups and therefore a greater number of individuals. Among the given options, 'Class' is the highest rank, making it the most inclusive group compared to order, family, and species.

Common mistake: Students often mistakenly choose 'species' because it is the fundamental unit of classification, but it is actually the least inclusive (most exclusive) group, containing the smallest number of individuals.

Living things grow by adding new cells from within, a process called intussusception. However, non-living things like crystals or a heap of sand can also increase in size by adding more materials to their surface, a process called accretion. This means that simply increasing in size is a characteristic that can be seen in both living and non-living things, making it not a definitive sign of life on its own.

Common mistake: Students often mistakenly choose 'increase in biomass' because they confuse it with a general increase in size, but biomass specifically refers to the mass of living matter.

An onion cell is a plant cell, while a cheek cell is an animal cell. A key difference is that plant cells possess a rigid outer cell wall made of cellulose, which provides structural support and a fixed shape. Animal cells, like the cheek cell, lack this cell wall, having only a flexible cell membrane as their outer boundary.

Common mistake: Students often mistakenly choose chloroplast because it is a key feature of plant cells, but they forget that onion bulb cells grow underground and do not photosynthesize, so they lack chloroplasts.

The testis in mammals is the organ responsible for producing male gametes, which are sperm cells. In flowering plants, the anther is the part of the stamen that produces pollen grains. Since these pollen grains contain the male gametes for the plant, the anther performs a similar function to the testis.

Common mistake: Students may confuse the anther with the filament, forgetting that the filament is just the stalk that supports the anther, which is the actual site of pollen production.

Bacteria are classified based on their shape and how they are arranged. The term 'cocci' refers to spherical or round bacteria. The prefix 'strepto-' means the bacteria are arranged in a chain, so streptococci are spherical bacteria that grow in chains.

Common mistake: Students often confuse streptococci with staphylococci; staphylococci are also spherical bacteria but are arranged in grape-like clusters, not chains.

The question asks to identify the most numerous group in the animal kingdom. Class Insecta, which includes insects, is the largest and most diverse group of animals on Earth, making up over 80% of all known animal species. This makes them the most abundant group, far outnumbering mammals, birds, or annelids.

Common mistake: Students might mistakenly choose Mammalia because they are the most familiar animals to humans, but in terms of the sheer number of different species, insects are overwhelmingly more numerous.

Radial symmetry is a body plan where an organism can be divided into two identical halves by any plane passing through its central axis, similar to how a pie is cut. This feature is characteristic of the phylum Coelenterata, which includes animals like jellyfish, hydra, and sea anemones. The other options listed, such as Platyhelminthes (flatworms) and Arthropods (insects), exhibit bilateral symmetry, meaning they only have one plane that divides them into two mirror-image halves.

Common mistake: Students often confuse the different types of body symmetry and may incorrectly choose Arthropods, a very common phylum, without recalling that they have a distinct head and tail region, which is a feature of bilateral symmetry.

The dorsal fin is located on the back of the fish and acts like the keel of a boat. Its main job is to provide stability and prevent the fish from rolling over in the water. This makes it the most important fin for balancing, especially during sudden turns or stops.

Common mistake: Students often confuse the pectoral fins' function of steering and stopping with the dorsal fin's primary role in preventing the fish from rolling over, which is the main aspect of balancing.

A duck's beak is broad and flat, which is a structural adaptation for its feeding habit in water. This shape allows it to scoop up water and mud containing small plants and animals. The edges of the beak have special comb-like structures called lamellae that act like a sieve, letting the water and mud drain out while trapping the food inside.

Common mistake: Students may mistakenly choose 'picking and cracking food' because they confuse the duck's specialized beak with the short, strong beaks of seed-eating birds like finches or domestic fowls.

The greatest challenge for animals moving from water to land is preventing their bodies from drying out. The reptile's dry, scaly skin is made of a waterproof protein called keratin. This skin acts as a barrier, significantly reducing water loss and allowing reptiles to live in dry terrestrial environments far from a constant water source.

Common mistake: Students often mistakenly choose the amniotic egg because it is also a key adaptation for life on land, but the scaly skin is more fundamental as it allows the adult animal itself to survive away from water by preventing dehydration.