evolution chapter 9 Flashcards
what is a population
organisms of same species that live in a specific area
micro-evolution
small scale evolution
- change in gene frequencies within a population over time
macro-evolution
evolution on a grand scale
- changes occur over a long period of time
genetic equilibrium
stable condition of a population in which an allele frequency remains the same over generations
allele frequency
percentage of any specific allele in a gene pool
- when frequency of allele changes
what factors change the allele frequencies of a population
- mutations
- gene flow
- non-random mating
- genetic drift
- natural selection
mutations
- changes in dna of individual
- provide new alleles in population and may provide variation required for evolution to occur
ex: norway rat- warfarin resistant rats in norway caused increase in rat population
gene flow
net movement of alleles from one population to another
ex: grey wolf- may mate with member of nearby population to bring new alleles
what are the 3 types of mutations
beneficial, neutral, harmful
beneficial mutations
potential to increase an individuals ability to survive or fitness
neutral mutations
don’t affect an individual’s ability to survive or fitness
harmful mutations
occur most often, environment selects against them, results in rare alleles
ex: cystic fibrosis
compare how a small population vs. large population would be affected by genetic drift
smaller the population, less likely that parent’s gene pool will be reflected in next generation, vice versa
what are the 3 types of natural selection
(know graphs)
- stabilizing
- directional
- disruptive
difference between founder’s effect and gene flow
founders: starting a new population
gene flow: increases genetic diversity- may help population survive
define species
group of interbreeding organisms that share gene pool and produce fertile offspring
- isolated from other species
- same species can exchange genes
what are the 5 types of pre-zygotic mechanisms
(prevention of mating)
- behavioural isolation
- temporal isolation
- ecological habitat isolation
(prevention of fertilization)
- mechanical isolation
- gametic isolation
behavioural isolation
behaviour that prevents interbreeding with closely related species
ex: mating rituals
habitat isolation
species in same area occupy different habitats, rarely encounter each other
ex: garter snakes in water and meadows
temporal isolation
species kept separate due to timing barriers, mate at different times (seasons, years, etc.)
ex: flowering
mechanical isolation
related species anatomically different, can’t mate
ex: variations in flower structure prevent pollination
gametic isolation
sperm can’t reach or fertilize egg
ex: plants may land on stigma- fertilization doesn’t occur
what are the 3 post-zygotic mechanisms
- hybrid inviability
- hybrid infertility
- zygote mortality
hybrid inviability
develops but can’t survive to maturity
ex: cotton plants- produce weak and sterile seeds
