ENV100Y5 Lecture Notes - Lecture 16: Sympatric Speciation, Directional Selection, Allopatric Speciation
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ENV100Y5 Full Course Notes
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Natural selection: traits enhance survival and reproduction persist in populations, therefore they evolve over time and they can diverge to form new species. Darwin: evolutionary change by descent with modification. Evolution: change in genetic composition of a population. Mechanisms of evolution: mutation, migration, random drift, natural selection. Genetic variation: mutations, accidental changes in dna that may be passed on to offspring, provides genetic variation on which selection acts. Mutation in myostatin gene produce double muscling belgina blue cattle. Natural selection: individuals vary, not all will survive to reproduce, success not usually random, parents pass traits on to offspring. Directional selection: drives feature in one direction (neck length) Stabilizing selection: selection against extremes ( horse size) Disruptive selection: traits diverge in two or more directions ( leads to new species) Allopatric speciation: geographic isolation leads to speciation, forest vs. savannah elephant. Sympatric speciation: populations become reproductively isolated within the same area extinction=disappearance of a species from earth.
