- Evolution, which is change in species over multiple generations (Figure7.2).
- Natural selection, in which individuals of a population that are most likely to survive
and reproduce are also most likely to pass on traits that have a genetic basis to any
offspring. - Adaptation, which are traits that help a plant or animal survive and reproduce in a
particular environment. Adaptations are the result of natural selection. For example,
light-colored moths on dark trees might be easier for birds to see and catch than dark
moths on dark-colored trees. If the moths’ color has a genetic basis, then after many
generations of birds catching more light moths than dark moths, the population of
moths will consist mostly of dark moths.
Figure 7.2: Humans and the other apes in this drawing all evolved from a common apelike
ancestor. ( 2 )
IneverydayEnglish, ”evolution”simplymeansto”change”ora”stepwisechangefromsimple
to complex.” In biology, evolution means change in the inherited traits of a group of organ-
isms over multiple generations (Figure7.3). Biological evolution has changed biologists’
understanding of all life on Earth.
Darwin’s Observations
Most people in the world did not become aware of the theory of evolution until 1859, when
Charles Darwin published his bookOn the Origin of Species by Means of Natural Selection.
Thisbookdescribedtheobservationsandevidencethathecollectedover20yearsofintensive
research, beginning with a five-year voyage around the world on a British research ship,
the HMS Beagle. During this five-year voyage (Figure 7.4), Darwin was able to make
observations about plants and animals spread around the world, and to collect specimens
to study when he returned to England. Each time the Beagle stopped at a port to do some