DENDROLOGY

Detailed explanation-1: -Genetic Variation is Essential for Evolution by Natural Selection. For natural selection to occur, a population must have a wide variety of individuals with different traits. For example, natural selection would not influence fish body color if all individuals in a population were exactly the same color.

Detailed explanation-2: -Genetic variation is essential for natural selection because natural selection can only increase or decrease frequency of alleles that already exist in the population.

Detailed explanation-3: -Natural selection happens only if the following four requirements are met, according to evolution theory. They are as follows: heredity, reproduction, physical traits that differ, and variation in the number of offspring produced by each individual.

Detailed explanation-4: -Evolution by natural selection is the inevitable consequence of three simple conditions: variation, inheritance, and differential reproductive success. Natural selection does not act directly on genotypes: It operates on phenotypic differences among the individuals in a population.