evolution
change in the genetic makeup of a population over time; descent of modification
natural selection
individuals that have certain traits tend to survive and function at higher rates other than individuals bc of those traits
fitness
the ability to survive and reproduce
two theory based on natural selection
- traits are heritable
- more offspring is produced than survived
adaptations
inherited characteristics of an organism that enhances their survival and reproduction
mutations can be
harmful, beneficial, neutral
examples of random occurrences
- migration/gene flow
- mutations
- genetic drift
genetic drift
a change in events that causes a change in allele frequency from one generation to the next
two types of genetic drift
bottleneck effect: when a population is reduced by a non-selective disaster (floods, fires, hurricanes, hunting)
founder effect: when some become isolated from a large population and establish a small population with a gene pool that differs from the large population
gene flow
the transfer of alleles into or out a population due to fertile individuals or gametes
5 conditions that meet Hardy Weinberg
- no mutations
- no gene flow
- no natural selection
- random mating
- large population size
evidence of evolution
- fossils
- comparative morphology
- biogeography
vestigial structures
structures with little or no use
homologous structures
same structure but different function (common ancestor)
analogous structures
different structure but same functions (different ancestor)
to determine evolutionary relationships scientist use
- DNA
- fossils
- homologous structures
allopatric vs sympatric
allopatric: physical barrier divides population (often caused by natural disasters)
sympatric: a new species evolves while still inhibiting the same geographic region as the ancestral species
describe and list the 5 prezygotic barriers
- habitat isolation: species live in different areas and unable to mate
- temporal isolation: species breed at different times of the year or season
- behavioral isolation: unique behavioral patterns separate species
- mechanical isolation: the reproductive anatomy does not fit with another species
- gamete isolation: do not allow for the egg and sperm to fuse
3 postzygotic barriers
- reduced hybrid viability: impair the hybrids development of survival
- reduced hybrid fertility: hybrid are not fertile (can’t reproduce)
- hybrid breakdown: hybrid of first gen may be fertile but when they mate again their offspring will be sterile
puntuated equilibrium vs gradualism
PE: evolution occurs rapidly after a period of stasis (no change over long periods of time)
gradualism: evolution occurs slowly over many years
divergent evolution
groups with the same common ancestor evolve differences resulting in the formation of a new species
convergent evolution
two different species develop similar traits
