LIFE SCIENCE

Detailed explanation-1: -Evolution can occur if there is genetic variation within a population. Variation comes from mutations in the genome, reshuffling of genes through sexual reproduction and migration between populations (gene flow).

Detailed explanation-2: -These factors are the “forces of evolution.” There are four such forces: mutation, gene flow, genetic drift, and natural selection.

Detailed explanation-3: -Evidence for evolution: anatomy, molecular biology, biogeography, fossils, & direct observation.

Detailed explanation-4: -The essence of Darwin’s theory is that natural selection will occur if three conditions are met. These conditions, highlighted in bold above, are a struggle for existence, variation and inheritance. These are said to be the necessary and sufficient conditions for natural selection to occur.