Evolution and Adaptation Flashcards
Phenotypic traits may be … or …
Discrete, Continuous
Polygenic
Phenotypes can be determined by one or many genes. Polygenic control means continuous variation. Not discrete.
Pleiotropy
One gene can affect more than one trait
Directional Selection
Individuals at one extreme are disadvantaged. Frequency curves shifts to favored phenotype. Mean average value of the phenotype changes.
Stabilizing Selection
Intermediate phenotype favored. Removes harmful genetic variation. When environment is relatively unchanging.
Disruptive Selection
Individuals at both extremes favored. Relatively uncommon. Increases phenotypic variation. Can lead to biological speciation. Very rare
Genetic Drift
Random fluctuations in a gene pool over time can cause variation to be lost. Important in small populations
Two random processes
Bottle neck and founder effect
Bottleneck effect
Large reduction in genetic diversity due to decrease in population size
Founder effects
Small numbers of colonizers start new population with small amount of genetic variation
Phylogenetic tree
Represent patterns of relatedness between different species
Species
Group of organisms that naturally interbreed with each other and produce fertile offspring
Allopatric Speciation
The evolution of new species due to geographic isolation. Most common mechanism of speciation.
Sympatric Speciation
Evolution of new species without geographic isolation. Can be caused by small scale habitat variation, and resource diversity
Polyploid
An organism that has 3+ sets of chromosomes (diploid gamete). Genetically distinct from parents, unable to breed with a diploid. Can cause sympatric speciation
