Natural Selection

Evolution

Change in the gene pool over time

Macroevolution

Large-scale changes in species over time

Microevolution

Small-scale changes in genotype frequency over time

Directional selection

Polygenic organisms selecting the most favorable genes during evolution (causing allele frequency to shift in one direction)

Fossils

Remains/traces of organisms from the past in sedimentary rock layers

Darwin's focus on adaptation

Adaptation to the environment and origin of new species are closely related processes

Genetic variation

Members of a population vary in inherited traits

Zone of tolerance

Average zone where species survive and thrive

Natural selection

Heritable traits survive and reproduce at a higher rate, increasing match between organisms and environment

Fitness

Measured by an organism's ability to survive and reproduce, determining genetic contribution to the next generation

Evolution vs Natural selection

Evolution is gradual change in inherited traits, while natural selection is the survival of the best-suited individuals

Divergent evolution

Species adapt to different environments and ecological roles

Artificial selection

Humans modify species by selecting and breeding individuals with desired traits

Gene pool

All alleles in a population

Genetic drift

change in the allele frequency of a population due to randomness

Founder effect

Individuals become isolated from a larger population

Bottleneck effect

Sudden reduction in population size leading to loss of genetic variation

Gene flow

Movement of alleles among populations, immigration & emigration

Reproductive isolation

Barriers impeding two species from creating viable fertile offspring

Adaptive radiation

Rapid evolution of diversely adapted species from a common ancestor

Homology

Similarity due to shared ancestry

Analogy

Similarity due to convergent evolution

Convergent evolution

Similar environmental pressures produce similar adaptations in unrelated organisms

Divergent evolution

Species sharing common ancestry become more distinct due to differential selection pressures.

abiotic factors effecting rate of evolution

light - distribution patterns of photosynthetic organisms, Water, root size, Pollution

Biotic factors affecting rate of evolution

special distribution patterns, location of food, proximity to other packs, predator-prey relationships, competitions, causes both populations to fluctuate

why natural selection isnt perfect

1. selection can act on only existing variations

2. evolution is limited by historical constraints

3. adoptions are often compromises

4. Chance, natural selection, and the environment interact

punctuated equillibrium

species undergo long periods of little evolutionary change, punctuated by relatively brief periods of rapid evolution or speciation events.

gradualism

evolution occurs gradually over long periods of time through the accumulation of small, incremental changes