ap bio unit 7

Evolution

The gradual change of a species over time to better suit their environment.

• The current accepted theory for evolution was created by Charles Darwin during the 1880s

Adaptation

An inherited trait that makes an organism more fit for its environment.

• “Fitness” refers to an organism’s ability to reproduce

• Example: large beaks are an adaptation of some finches, which allows them to crack open seeds

Niche

Refers to the role or function of an organism or species in an ecosystem.

• Example: an organism’s food source, where it lives, what services it provides to an ecosystem, etc.

• Organisms or species with overlapping niches leads to competition

Natural Selection

A process in which individuals with favorable inherited traits are more likely to survive and reproduce.

• Natural selection is the mechanism, or driving force, of evolution

Artificial Selection

Where humans modify other species by selecting and breeding individuals with desired traits.

Key Features of Natural Selection

• Members of a population often vary in their inherited traits

• All species can produce more offspring than the environment can support, and many of these offspring fail to survive and reproduce.

• Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to have more offspring than other individuals.

• This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations.

• Note that populations, not individuals, evolve over time

• Natural selection can only increase or decrease existing heritable traits that vary in a population. It does not create new traits.

• The traits that are adaptive will vary with different environments.
  

Requirements for natural selection to occur

• Competition: More offspring must be produced than can be supported by the environment.

• Variation: Offspring must be produced with traits that differ from one another.

• Adaptation: Certain variations must be more advantageous than other variations. Some individuals must be more likely to survive and reproduce.

• Heritability: The favorable trait, or adaptation, must be genetic and capable of being inherited by the next generation.

Homologies

Similarities between species resulting from common ancestry.

Homologous structures

Anatomical similarities between species that share a similar function, but not necessarily the same function.

• Example: The image shows these animals share the same basic structure of bones.