Question

many traits, such as body size and metabolic rate, are widely variable throughout a population because
a. they are influenced by a single gene.
b. they are influenced by more than one gene.
c. they cannot be influenced by environmental factors.
d. they are not influenced by genes in any way.

Explanation:

Traits like body size and metabolic rate are polygenic, meaning they are influenced by multiple genes (polygenic inheritance). A single gene usually controls traits with distinct phenotypes (like Mendelian traits), so option A is wrong. Environmental factors can influence these traits (e.g., nutrition affects body size), so C is wrong. Genes do influence these traits, so D is wrong. Thus, the correct answer is B as these traits are influenced by more than one gene, leading to wide variation in a population.

Answer:

B. they are influenced by more than one gene.