How can major geologic events and changes in organisms provide evidence for constructing a timeline of earth’s history?

In a relatively small iguana population the allelic frequency is tracked for three generations. webbing is a recessive allele; no webbing is the dominant allele. during one very rainy spring and summer, a flood washes all the iguana without webbed feet out to sea. by the fall, and three generations later, you have the gene pool seen here.

What must be true for natural selection to heppen

What is the difference between how ionic and covalent bonds form