darwins theory natural selection

Darwin’s Delay in Publishing

Darwin delayed publishing his theory for 20 years to gather evidence because his ideas were radical and contradicted established science.

Alfred Russel Wallace

A British naturalist who independently developed a theory of evolution similar to Darwin’s, prompting Darwin to publish his work.

Natural Selection

The process by which organisms with variations best suited to their environment survive and reproduce more successfully.

Struggle for Existence

Competition among organisms for limited resources, since more offspring are produced than can survive.

Variation

Genetic differences among individuals in a population, caused by mutation and sexual reproduction.

Adaptation

A heritable trait that increases an organism’s ability to survive and reproduce in its environment.

Fitness

The ability of an organism to survive and reproduce in its environment, passing its genes to the next generation.

Differential Reproductive Success

The idea that individuals with better adaptations produce more offspring than others.

Conditions for Natural Selection

Occurs when (1) more offspring are born than survive, (2) heritable variation exists, (3) variation affects fitness, and (4) better adapted individuals reproduce more.

Survival of the Fittest

The process where organisms best adapted to their environment survive and reproduce most successfully.

Descent with Modification

The passing on of traits from ancestors to descendants with changes over generations, leading to new species.

Common Ancestry

The principle that all living species share ancient common ancestors.

Fossil Record

Evidence of descent with modification over long periods of time, supporting evolutionary theory.

Deep Time

Geological time scales that provide enough time for natural selection to cause evolutionary change.

Artificial Selection

Human-directed breeding for desired traits, similar to natural selection but controlled by humans.

Adaptation Examples

Physical (claws, beaks), physiological (hibernation), behavioral (tool use) traits that help organisms survive.