lecture 4 - evolution and ecology Flashcards
what is evolution (taylor’s version)
descent with modification
allele frequency change
what are the mechanisms of evolution
mutation
natural selection
genetic drift
gene flow
how do mutations arise
copying errors during cell division, mechanical exchange, exposure to chemicals, or high energy radiations
what are the types of natural selection
directional selection, stabilizing selection, disruptive selection
directional selection
individuals at one phenotypic extreme are favoured
stabilizing selection
individuals w intermediate phenotype are favoured
disruptive selection
individuals at both phenotypic extremes are favoured
mutation vs recombination
mutation provides raw material on which evolution is based
recombination and independent assortment rearrange the raw material into new combinations
genetic drift
occurs when chance events determine which alleles are passed to the next generation
only significant for small pops
why are adaptations not perfect
lack of genetic variation
evolutionary history
ecological trade offs
environments are constantly changing and there are constraints on evolution
adaptive evolution
a process of change in which traits confer survival advantages to increase in frequencies overtime
gene flow
alleles move between pops via movement of individuals or games
pops become more similar
trophy hunting case study
trophy hunting removes the largest and strongest males
observed in
- african elephants for ivory
-rock shrimp commerical harvesting takes largest individuals which are all females
phenotype
observable characteristics that are determined by the genotype
genetic drift has 4 effects on small pops
acts by chance alone, causes allele freq to fluctuate at random
genetic variation of pop is reduced
freq of harmful alleles can increase
differences between pops can increase
