Final answer:
The main conditions for evolution by natural selection are variation, inheritance, and differential reproduction. Genetic variation is a result of mutation and recombination and is essential for evolution to occur. Selection pressures affect which traits are adaptive, influencing evolutionary change. The correct option is A.
Step-by-step explanation:
To explain the conditions required for evolution by natural selection, we must consider several key components:
- Variation: There must be differences among individuals within a population. For natural selection to drive evolutionary change, these variations must have a genetic basis to be inherited by the next generation.
- Inheritance: Genetic characteristics must be passed from parents to offspring. Without inheritable traits, advantageous or disadvantageous variations cannot be acted upon by natural selection.
- Differential reproduction: Individuals with certain traits must have higher reproductive success, thus passing on those traits to a greater proportion of the next generation.
Existence of Genetic Variation in Populations
Genetic variation virtually always exists within a population due to the following:
- Mutations: Random changes in the DNA sequence can create new genetic information and traits.
- Recombination: During sexual reproduction, the mixing of genetic material from two parents produces new combinations of genes.
This genetic diversity is crucial for populations to adapt to changing environments and for evolutionary processes to occur.
Environmental factors exert selection pressure that impacts which traits are adaptive and therefore more likely to be passed on. When environmental conditions remain constant, evolutionary stasis can occur as there is less pressure for change.