microevolution : one long argument Flashcards
lecture 8 - Pete Cotton
Dawin’s 1st postulate
individuals within population are variable
Darwin;s 2nd postulate
some variations are passed on to offspring
Darwin’s 3rd postulate
some individuals are more sucsessful at surviving and reproducing than others
Darwin’s 4th postulate
the survival and reproduction of individuals are not random - individuals that survive and reproduce the most are those with most favourable variations
cladogenesis
the formation of a new group of organisms or higher taxon by evolutionary divergence from an ancestral form.
microevolution
changes in the frequency of a gene in a population
macroevolution
evolution of groups larger than an individual
anagenesis
evolutionary changes can occur in a species over time to a sufficient degree that later organisms may be considered a different species
the ‘ struggle for existance ‘
Malthus : animal populations should outgrow limited resources very quickly
individuals with advantagous variations would do better in the struggle for survival
these indivuals would produce more offspring
adaptation
a trait that enables an organism to survive and reproduce better tahn if it lacked the trait
fitness
a measure of individual success in evolutionary terms (reproductive success)
The average number of offspring produced by individuals with one genotype relative to the number produced by individuals with different genotypes
natural selection
the differential reproductive success of differnt heritable phenotypes
directional selection
mode of negative natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype
stabilising selection
descriptive term for what happens to an individual trait when the extremes of the trait are selected against
disruptive selection
a type of natural selection that selects against the average individual in a population
