Final answer:
Natural selection can occur when there is variation, heritability, selection pressure, and reproduction.
Step-by-step explanation:
Natural selection can only occur when certain conditions are met:
- Variation: There must be differences among individuals in a population.
- Heritability: These differences must be genetic and can be passed down from one generation to the next.
- Selection Pressure: There must be selective pressures in the environment that favor certain traits over others.
- Reproduction: Individuals with favorable traits must be able to reproduce and pass down their traits to the next generation.
These conditions allow for the process of natural selection to occur, leading to the evolution of populations over time.