Key terms:. Species. A biological species is: a group of organisms that can interbreed and are reproductively isolated from other such groups. Each of these butterflies is a different species (there are thousands of different species of butterfly which do not interbreed). Populations.
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Example: human population, Arctic tundra plant species
Example: Some frog species
A gene pool made up of 16 individuals
For example: closely related species of the dog family can interbreed
Also, species can show a gradual change in phenotype over a geographical area. This gradual change is called a cline. This often occurs over the length of a country or continent.
Coyote–red wolf hybrids
Canis familiaris dingo
Clines Species can show a gradual change in phenotype over a geographical area. This gradual change is called a cline. This often occurs over the length of a country or continent.
If a cline forms a ring, (eg. across a continent) demes A and E may be unable to breed when they meet, although, the intermediate forms can still interbreed. Are A and E still the same species or two separate species?
A’AChanging Allele Frequencies
with other gene pools as individuals
move between them.
frequencies can change randomly
from generation to generation.
Natural selection: Selection pressure againstcertain alleles combinations may reduce reproductive success.