Study Guide for Evolution Quiz
Key Terms:
1. Species – a group of organisms whose members can successfully reproduce.
2. Population - organisms of one species that live in the same place.
3. Variation - Different form of a characteristic or trait. Natural variations occur in a
species.
4. Adaptation - Any variation that makes an organism better suited to its environment.
Adaptations can be in the form of color, shape, behavior and chemical make-up
differences.
5. Limiting factors - availability of food, disease, space, predator and prey relationships
– have an impact on population size.
6. Mutation - a random, spontaneous change in the DNA. Mutations can be passed on the
next generation.
7. Evolution - change in the characteristics of organisms within a species over long
periods of time.
8. Natural Selection – Helpful variations (adaptations) within a population that enables
some members of a species to be better adapted to the environment, and thereby
reproduce at a higher rate than those organisms without the adaptation.
Charles
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Darwin
English naturalist (someone who studies nature) who lived in the middle 1800’s.
Sailed around the world on the HMS Beagle as the ship’s naturalist.
Stopped at Galapagos Islands off the west coast of South America near Ecuador. He
observed several species of plants & animals that were similar to species in South
America, and yet uniquely different. For example, he noticed that the beaks of
finches (type of bird) differed not only from finches on the mainland, but also from
each other (see image on next page).
 Based on his travels and observations, Darwin wrote "On the Origin of Species by
Means of Natural Selection" which describes his theory of natural selection which is
still accepted today as an explanation of how species change over long periods of time
in response to changes in the environment.
Darwin's theory of natural selection has four parts:
1. Organisms produce more offspring than are capable of surviving. Due to limiting factors,
such as availability of food or shelter, not all offspring will survive. Only some of the
individuals survive to adulthood.
2. Inherited variations are found among individuals of a species. Individuals in a population
are slightly different from one another. Within a species, individuals have different
forms of traits. For example, in humans, some people have attached ear lobes, while
others have free ear lobes. Variations are caused by mutations in the DNA and can be
inherited.
3. Some variations enable individuals of a population to survive and reproduce better than
others. These helpful variations are called adaptations. Individuals with an adaptation
have an increased chance of survival in the environment in which resources may be
limited.
4. Over time, those individuals with adaptations will make up more and more the population
because they are more likely to survive and reproduce. These individuals will produce
offspring with the inherited adaptation that are also well adapted to their environment.
Those members of a population with variations not well suited to the environment are
more likely to die early or produce fewer offspring.
In a population of organisms, there are two possibilities:
Mutations in DNA genetic variationadaptationssurvival & reproduction
OR
Mutations in DNA genetic variation no adaptationsextinction