* Evolution is about changes in gene frequencies: Evolution is the change in the genetic makeup of a population over time. This means the proportions of different alleles (versions of genes) within the population change.
* Individuals don't change their genes: While an individual might develop traits during their lifetime due to environmental factors (like building muscle through exercise), these changes are not passed on to their offspring. Their genes remain the same.
* Species are a collection of populations: A species is a group of populations that can interbreed and produce fertile offspring. The evolution of a species happens as a result of the evolution of its constituent populations.
Think of it this way:
Imagine a population of butterflies with varying wing colors. If a new predator favors butterflies with darker wings, the lighter butterflies are less likely to survive and reproduce. Over time, the proportion of darker-winged butterflies in the population increases. This is evolution - the genetic makeup of the population has shifted.
So, individuals don't evolve, but their genes contribute to the evolution of the population they belong to. And the evolution of multiple populations can eventually lead to the evolution of a species.
