Unit 1: Evolution Flashcards
Theory of Evolution provides direction for predictions about
living things in ongoing experiments
Evolutionary change
changes in populations over time
Natural selection
favorable traits survive and reproduce at higher rates. A process causing evolution.
Descent with modification
change in populations over generations
The idea of evolution by natural selection was discovered by
Charles Darwin
Natural selection can only take place if (3)
there is variation, heritable traits and effects of fitness.
Genetic diversity in a population comes from two main mechanisms
mutation and sexual reproduction.
Adaptation
a heritable trait that helps an organism’s survival and reproduction in its present environment
Beneficial alleles allow
An increasing of frequency in the population
Deleterious alleles result in
A decreasing of frequency in the population
Individuals that leave relatively more offspring have high
Evolutionary fitness
Ways selection can affect population variation include
stabilizing selection, directional selection, diversifying selection, frequency-dependent selection, and sexual selection
Stabilizing selection
When natural selection favors an average phenotype, selecting against extreme variation (qualitative characteristics)
Directional selection
selects for phenotypes at one end of the spectrum of existing variation (those who fit the environment best)
Diversifying Selection
Sometimes two or more distinct phenotypes can each have their advantages for natural selection, while the intermediate phenotypes are, on average, less fit. (very large or very small survive but not medium size)
