The two main sources of genetic variation are
Recombination and mutation
Single-gene traits and polygenic traits
Genotypes and phenotypes
Directional selection and disruptive selection

Cells a and b are the same size and shape, but cell a is metabolically quiet and cell b is actively consuming oxygen. oxygen will diffuse more quickly into cell because . b the oxygen molecules inside cell b have a higher kinetic energy b. a its membrane transport proteins will not be saturated c. a the diffusion gradient there is shallowerd. b the diffusion gradient there is steeper