Natural Selection
Adaptation
Variation
Mutation
Adaptation
Variation
Mutation
A random change in an organism's DNA sequence that serves as the ultimate source of new genetic variation.
What is a mutation?
In evolutionary terms, this concept does not mean physical strength, but rather an organism's ability to survive and successfully pass its genes to the next generation.
What is evolutionary fitness?
An adaptation that allows an organism to blend into its surroundings to hide from predators or prey.
What is camouflage?
Anatomical structures that are similar in different species because they were inherited from a common ancestor, like the limb bones of a human, whale, and bat.
What are homologous structures?
The rapid evolution of bacteria to survive medications meant to kill them, often cited as a modern, real-time example of natural selection.
What is antibiotic resistance?
The process by which organisms better suited to their environment tend to survive and produce more offspring.
What is natural selection?
This occurs when two or more species or individuals vie for the same limited resources, such as food, water, or nesting sites.
What is competition?
The breeding of dogs, livestock, or crops by humans to emphasize specific desirable traits.
What is artificial selection?
The evolutionary process by which populations evolve to become distinct, isolated species that can no longer interbreed.
What is speciation?
A type of natural selection where the environment favors one extreme trait over the other, shifting the entire population curve in one direction.
What is directional selection?
Any heritable trait, such as a hawk's sharp eyesight or a cactus's water-storing stem, that improves an organism's ability to survive and reproduce.
What is an adaptation?
This historical archive of life shows that older sedimentary rock layers contain simpler organisms, while younger layers contain more complex ones.
What is the fossil record?
Unlike natural selection, this mechanism causes trait frequencies to change purely by random chance, usually affecting small populations.
What is genetic drift?
Structures that have lost all or most of their original function through evolution, such as the human appendix or the pelvic bones of a whale.
What are vestigial structures?
When two populations are capable of mating but do not because they have different courtship rituals, dances, or mating songs.
What is behavioral isolation?
Natural selection cannot occur without this pre-existing condition, which ensures that individuals within a population have different physical or behavioral traits.
What is genetic variation?
Scientists use the fossil record to look for these types of organisms, which show how a species gradually changed from an old form into a new form over time.
What are ancestral forms?
A type of genetic drift that occurs when a sharp reduction in the size of a population due to a sudden disaster (like a wildfire or flood) severely alters the remaining traits.
What is the bottleneck effect?
Besides looking at bones, scientists compare this molecular code found in all living things to see how closely related two species are.
What is DNA?
This type of natural selection favors individuals at both extremes of a trait's range, while selecting against the average or middle individuals.
What is disruptive selection?
While most mutations are neutral or harmful, this specific type of mutation provides an advantage to an organism in a changing environment.
What is a beneficial mutation?
Because organisms produce more offspring than the environment can support, this phrase describes the intense rivalry between individuals to get enough resources to survive.
What is competition?
A type of genetic drift that happens when a few individuals leave a large population and start a brand-new colony, carrying only a small fraction of the original group's traits.
What is the founder effect?
This type of isolation occurs when a physical barrier, like a mountain range, canyon, or river, splits a population into two groups so they can no longer mate.
What is geographic isolation?
This type of selection favors the average or middle individuals in a population, while selecting against both extremes (like human birth weights being mostly in the middle).
What is stabilizing selection?