JAMB Biology Past Questions & Answers - Page 87

A saprophyte or saprotroph is an organism which gets its energy from dead and decaying organic matter. This may be decaying pieces of plants or animals. This means that saprophytes are heterotrophs. They are consumers in the food chain.

Xylem transports water and mineral salts from the roots up to other parts of the plant, while phloem transports sucrose and amino acids between the leaves and other parts of the plant.

The xylem, vessels, and tracheids of the roots, stems, and leaves are interconnected to form a continuous system of water conducting channels reaching all parts of the plants.

Conjugation consists of the temporary union of two organisms and the exchange of micronuclear elements.

Earthworms don't have red blood because they exchange gas with their skins. The color of blood is red due to the presence of hemoglobin in the red blood cell that helps transport oxygen.

Root hair cells are adapted to absorb the water out of the soil by osmosis– they have a large surface area, thin walls, and are close to the xylem cells used to transport water up the plant. Minerals such as nitrate ions cannot be absorbed by osmosis (which is the movement of water only) or diffusion (because the minerals are in very low concentration). The root hair cells have carrier molecules on their surface that pick up the minerals and move them into the cell against the concentration gradient. This requires energy, and is called active transport.