Mutations such as polyploidy and crossing over provide the genetic basis for a. evolution. c. biogenesis. b. spontaneous generation. d. sexual reproduction.

Evolution

Explanation:

Evolution is the gradual accumulation of genetic variations leading to the origin of a new better-adapted trait or population. The presence of genetic variations is required for evolution to occur. The evolutionary forces such as natural selection favor the beneficial genetic traits in the individuals. In the absence of genetic variations, evolution can not occur.

A mutation is a random change in the genetic material of living beings. Crossing over is the exchange of genetic material between homologous chromosomes during meiosis and produces new gene combinations. Both mutations and crossing over serve to add genetic variations in individuals of a population and facilitate the evolution.

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many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.