Evolution and natural selection

The idea that unifies all of biology. What Darwin proposed and how natural selection explains adaptation, without the typical misunderstandings.

Direct answer: Evolution is the change in the heritable characteristics of populations over generations. Natural selection (Darwin) is its main mechanism: because there is variation and more offspring are produced than survive, the best-adapted individuals leave more offspring and their traits become more common.

The conditions for natural selection

Variation: individuals in a population differ from each other.
Heredity: many of those traits pass to the offspring.
Overproduction: more individuals are born than the environment can support.
Differential survival and reproduction: the best-adapted leave more offspring.

Evidence for evolution

The fossil record, homologous structures, embryonic development and, above all, the DNA similarities between species support evolution.

Exam trap: natural selection is not "survival of the strongest", but of the fittest to reproduce in its environment. Also, the population evolves, not the individual, and it is not a process with a "purpose" or direction.

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Frequently asked questions

What is natural selection?

The mechanism by which individuals best adapted to their environment leave more offspring, and their traits become more frequent.

Who proposed the theory of evolution by natural selection?

Charles Darwin (together with Alfred Russel Wallace).

Does the individual or the population evolve?

The population. Individuals do not evolve during their lifetime; the frequencies of traits in the population change.