2025 - JAMB Biology Past Questions and Answers - page 1

An instrument designed to measure plant growth must be able to detect small increases in the length of a plant over time.

An auxanometer is specifically constructed for this purpose. It works by attaching part of the plant to a recording device that magnifies and measures even slight changes in length as the plant grows.

This allows scientists to accurately monitor the rate and amount of growth in plant structures such as stems or roots.

Therefore, the instrument used to measure plant growth is the auxanometer.

The interaction between organisms of different species can take several forms depending on whether one or both benefit.

Inside the rumen of cattle, bacteria and protozoa help break down cellulose found in plant material. This digestion produces nutrients that the cattle can absorb and use for energy.

At the same time, the microorganisms benefit because the rumen provides them with food and a suitable environment for survival.

Since both the cattle and the microorganisms benefit from this relationship, the association is classified as symbiosis, specifically a mutual form of symbiotic interaction.

Therefore, the correct answer is symbiosis.

Some structures in organisms exist in a reduced or non-functional form compared to similar structures in other organisms.

In herbivores, the caecum is large and plays an important role in digesting cellulose from plant material with the help of bacteria.

In humans, the appendix is a small structure attached to the intestine and does not perform the same major digestive function.

This indicates that the human appendix is a reduced remnant of a structure that was once functional in ancestral organisms.

Such reduced and non-functional structures are called vestigial organs, and they provide evidence of evolutionary change.

Therefore, the correct answer is vestigial organ.

An organism's hereditary information is stored in its DNA, which contains genes that determine inherited traits.

The specific combination of genes or alleles present in an organism represents its genetic constitution.

This genetic composition determines the traits that may be expressed, although the environment can influence how they appear.

The term used to describe the complete set of genetic information carried by an organism is genotype.

Therefore, the genetic makeup of an organism is called the genotype.

The survival of many organisms depends on their ability to avoid being seen by predators.

The green-brown colour of the grasshopper closely matches the colour of dry grass in its environment.

This similarity makes it difficult for predators to distinguish the grasshopper from its surroundings.

By blending into its environment, the grasshopper reduces the chance of being detected and eaten.

This type of adaptation is known as camouflage.

Therefore, the green-brown colour is an adaptation for camouflage.

When soil is mixed with water and allowed to stand, the particles separate according to their density and size.

Heavier mineral particles such as sand settle first, followed by lighter particles like silt and clay.

Organic matter, such as decaying plant remains, is less dense than mineral particles.

Because it is lighter, this organic matter does not sink but instead floats on the surface of the water.

Therefore, the correct statement is that decaying organic matter remains afloat.

Consider a cross between a plant that is homozygous tall with genotype TT and a plant that is homozygous short with genotype tt.

Each offspring receives one allele from each parent. The tall parent contributes the T allele, while the short parent contributes the t allele.

This results in all offspring having the genotype Tt, which is heterozygous.

Since the tall allele T is dominant over the short allele t, the offspring will show the tall characteristic.

Thus, the phenotype produced in the F₁ generation is heterozygous tall.

The human skeleton consists of many bones that vary in size and function.

The bone located in the upper leg, extending from the hip joint to the knee joint, is called the femur.

This bone is longer than any other bone in the body and supports the weight of the body during standing, walking, and running.

Because of its length and strength, it is recognized as the longest bone in the human body.

Therefore, the correct answer is femur.

An estuary is a region where freshwater from rivers mixes with saltwater from the sea.

This environment contains salty water and muddy soil, which many plants cannot tolerate.

Mangrove plants have special adaptations, such as salt tolerance and specialized roots, that allow them to survive in such conditions.

Because of these adaptations, mangroves are commonly found growing in estuarine habitats.

Therefore, the correct answer is mangrove.

Water transparency refers to how clearly light can pass through water, which indicates the amount of suspended particles present.

A secchi disc is a circular plate that is lowered gradually into the water until it can no longer be seen from the surface.

The depth at which the disc disappears gives a measure of the clarity of the water.

This method allows scientists to estimate the level of turbidity or suspended matter in the water.

Therefore, water transparency is measured using a secchi disc.