2024 - JAMB Biology Past Questions and Answers - page 3

Xerophytes are plants adapted to survive in environments with little water.Arid lands are characterized by very little rainfall and therefore contain the greatest concentration of xerophytes.

Continuous variation refers to traits that show a range of values with no distinct categories. Examples include height, weight, and skin color. Since there are no significant gaps between the extreme individuals in these types of variations, the description given in the question fits the definition of continuous variation.

The ground layer of a tropical rainforest is the lowest layer, receiving the least sunlight. Plants in this layer are typically small and shade-tolerant.* **Liverworts** are small, non-vascular plants that thrive in moist, shaded environments, which is characteristic of the forest floor.* **Obeche**, **mahogany**, and **oil palm** are all trees that are found in the upper layers of the rainforest, not the ground layer.

The cells responsible for transmitting messages to the effectors are motor neurons.* **Motor neurons** carry signals from the central nervous system (brain and spinal cord) to the effectors (muscles or glands), causing them to respond.* **Sensory neurons** carry signals from sensory receptors to the central nervous system.* **Hair cells** are sensory receptors found in the inner ear, responsible for hearing and balance.* **Relay neurons** (also known as interneurons) connect sensory neurons to motor neurons within the central nervous system.

Selective reabsorption primarily occurs in the proximal convoluted tubule, the loop of Henle, and the distal convoluted tubule. While the loop of Henle is involved in reabsorption, it focuses mainly on water and ions like sodium and chloride.* **A.** The glomerulus is where filtration happens.* **B.** Bowman's capsule receives the filtrate from the glomerulus.* **D.** The urethra is the tube that carries urine out of the body.

The central nervous system (CNS) is the control center of the body. It consists of the brain and the spinal cord, which work together to process information and coordinate responses.

The respiratory organ in mammals is the lungs. The lungs are responsible for gas exchange, taking in oxygen and releasing carbon dioxide. The other options are not respiratory organs:* Skin: Involved in protection and excretion.* Mouth: Part of the digestive system.* Heart: Part of the circulatory system, pumps blood.

The carbon cycle involves the movement of carbon atoms through various reservoirs (atmosphere, oceans, land, and organisms). Combustion is a process that releases carbon from organic matter (like fossil fuels or wood) back into the atmosphere as carbon dioxide.* **Evaporation:** Part of the water cycle.* **Nitrification:** Part of the nitrogen cycle.* **Transpiration:** Part of the water cycle.

Counter-shading is a camouflage strategy where an animal's body is dark on the top and light on the bottom. This helps the animal blend in with its environment, making it harder for predators to spot. Fish often exhibit this feature.* **A.** grasshopper: Grasshoppers use camouflage (e.g., green color to blend in with plants) but not counter-shading.* **B.** toad: Toads also rely on camouflage for protection, but not counter-shading.* **C.** fish: Fish often display counter-shading. From above, their dark backs blend with the darker ocean depths, and from below, their light bellies blend with the brighter surface.* **D.** chameleon: Chameleons are known for their ability to change color to blend with their surroundings, but it's not directly counter-shading.

The cochlea is the part of the inner ear that is responsible for hearing. It contains hair cells that transduce sound vibrations into electrical signals that are sent to the brain. The other options are involved in balance and equilibrium.