Unit 8
Genetic Drift
Random changes in gene frequencies within small populations, leading to divergence.
Types of isolation
Geographical Isolation - Members of a species become separated geographically, leading to the evolution of genetic differences and eventual speciation.
Temporal Isolation - Reproductive isolation occurs due to differences in breeding times between populations, resulting in the evolution of genetic differences and the formation of new species.
Behavioral Isolation - Species develop unique mating behaviors or rituals that prevent interbreeding with other species, leading to reproductive isolation and speciation.
Mutation - Changes in DNA sequences due to replication or repair errors, serving as the ultimate source of genetic variation.
Gene Flow - The movement of individuals between populations, introducing new genetic variations and influencing evolutionary trajectories.
Types of evolution
Convergent evolution - Unrelated species evolve similar traits or behaviors due to similar selective pressures.
Divergent Evolution - One species diversifies into two or more distinct species over time.
Coevolution - Two species influence each other's evolution through close ecological interactions, often resulting in reciprocal adaptations.
Types of natural selection
Directional Selection - Favoring one extreme phenotype within a population, driving evolutionary change towards that phenotype.
Stabilizing Selection - Favoring the average phenotype within a population, maintaining the status quo of traits.
Disruptive Selection - Favoring extreme phenotypes over the average, potentially leading to the divergence of populations and speciation.
Melanin - a complex polymer that produces pigment in skin
Bottleneck effect - occurs when a population's size declines dramatically because of some dramatic event. Random event when organisms disappear from the population and survivors have a smaller gene pool
Founder effect - when a small number of individuals establishes a new population and a loss of genetic variation ensues. This can lead to a new species.
Reproductive Isolation - occurs when a population splits into two groups and the 2 populations no longer interbreed. When population become reproductively isolated, they can evolve into two separate traits
Germ line mutations: occur in gametes and can be paasses down to offspring. Germline mutations can occur before fertilization and furing various stages of embryonic development. (Most important in evolution)
Somatic cell mutations: occur in all the other cells found throughout the organism and CANNOT be passed down to offspring
Non random mating - when a particular phenotype/genotype is preferred over others. This will make that phenotype more prevalent in the population than what will be expected.