2024 - JAMB Biology Past Questions and Answers - page 5

Gaseous exchange occurs directly through the plasma membrane in single-celled organisms and simple multicellular organisms.

• Paramecium: is a single-celled organism, and therefore it relies on diffusion across its plasma membrane for gas exchange.
• Hydra: While multicellular, it has a simple body plan where all cells are close to the external environment, and gas exchange occurs directly via diffusion.
• Flatworms and Earthworms: have more complex body plans and specialized respiratory structures (or, in the case of earthworms, their skin) for gas exchange, rather than relying solely on the plasma membrane.

The human vertebral column typically consists of 33 vertebrae:

• 7 cervical vertebrae (neck)
• 12 thoracic vertebrae (chest)
• 5 lumbar vertebrae (lower back)
• 5 sacral vertebrae (fused to form the sacrum)
• 4 coccygeal vertebrae (fused to form the coccyx or tailbone)

The schlerenchyma tissues are composed of dead cells that provide support and rigidity to plants.

The question refers to a diagram of an organ (unspecified in the prompt). Assuming this is a diagram of the kidney, the organ is responsible for osmoregulation. Osmoregulation is the process by which the kidney maintains the balance of water and electrolytes in the body.

Glycolysis is the process where glucose is broken down in the cytoplasm through a series of enzyme-catalyzed reactions. This process does not require oxygen (anaerobic). The products of glycolysis include pyruvic acid (also known as pyruvate) and ATP (adenosine triphosphate).

After fertilization, the zygote (formed by the fusion of the sperm and egg) undergoes cell division and differentiation to develop into an embryo.

• The fruit develops from the ovary.
• The seed contains the embryo.
• The endosperm provides nutrients for the developing embryo in some plants.

Darwin's theory of evolution is primarily based on the principle of natural selection. This means that organisms with traits that are better suited to their environment are more likely to survive and reproduce, passing those advantageous traits on to their offspring.

The hypothalamus is a region of the brain responsible for regulating several bodily functions, including body temperature, thirst, and hunger.

Here's the breakdown:

1. ATP Production in Glycolysis: Glycolysis produces a net gain of 2 ATP molecules.
2. Total ATP Produced: While 4 ATP molecules are produced during glycolysis, 2 ATP molecules are also used up in the initial steps.
3. Net Gain: 4 (produced) - 2 (used) = 2, but the prompt asks for the total produced during glycolysis, so the correct answer would be 4.

The xylem tissue in vascular plants is primarily responsible for the transportation of water and dissolved minerals from the roots to the rest of the plant.