Answer:
21. C
22. A
23. B
24. C
Explanation:
21. The structure of cell shape is not maintained by the cell membrane, Rather it is the product of the cytoskeleton which is the filaments and microtubules in the cell. They change the shape of the cell by contracting and relaxing. They also control the internal organization of organelles inside the cell.
22. Psychrophile bacteria thrive in low temperatures which they are adapted to. They can be expected in the polar regions and deep seas. Their metabolism can function in these low temperatures because their cells have antifreeze protein that protects the cells from ice-induced desiccation and damage.
23. Thermophiles are extremophiles that thrive in high temperatures. They can be expected in hydrothermal vents. They have heat-stable proteins and enzymes and DNA (that has high G-C content) that is not easily denatured at high temperatures.
24. This phase is called the stationary phase. The reproduction rate is equal to the death rate. This is because the population has reached its carrying capacity. This is why there is no growth in population.
