bio - ch 8 quiz

adaptive radiation

evolution from a common ancestor resulting in diverse species adapted to different environments

artificial selection

- a mechanism of microevolution

- microevolution can occur fast

- reduces genetic variability within a population

- can increase the frequency of harmful disorders

co-evolution

the process in which one species evolves in response to another

convergent evolution

distantly-related species that live in similar environments develops similar adaptations (analogous structures)

cumulative selection

the evolution of a simple structure into a more complex structure through a series of small adaptations ex. the eye in mammals

directional selection

individuals at one end of the phenotype range have a higher fitness than individuals near the middle or at the other end of the range

disruptive selection

takes place when individuals at the upper and lower ends of the range of phenotypes have higher fitness than individuals near the middle

gene flow

the exchange of genes with another population, occurs when fertile individuals migrate between populations. reduces genetic differences in populations. can usually mix neighbouring populations into a single population with a common gene pool

genetic drift

a change in the gene pool of a population due to chance

- smaller the population, larger the impact

bottleneck effect (genetic drift)

disasters like earthquakes drastically reduce the size of a population, also reducing the size of the gene pool

- some alleles may be more represented than others

- decreases genetic variation

founder effect (genetic drift)

the change in allele frequency relates to the genetic make up of the founders of a colony ex. human populations, like the amish have genetic diseases or traits commonly found within their population

gradualism

the evolution of species by gradual accumulation of small genetic changes over time

macroevolution

evolution over geologic time above the level of species, more dramatic biological changes ex. the evolution of tetrapods from aquatic vertebrates

microevolution

change in the allele frequencies within a population scale ex. shifts of phenotypes within species

mimicry

one species (the mimic) resembles another species (the model) in order to gain survival advantages ex. salamanders look like poisonous newts

post-reproductive barriers

- zygotic mortality (chromosomal incompatibility) ex, goat and sheep would not be viable)

- hybrid inviability (reduced fitness or early death) ex. tigers and leopards

- hybrid infertility (unsuccessful meiotic divisions) ex. horse and donkey --> mule <-- infertile

punctuated equilibrium

suggests that species often diverge in spurts of evolutionary change. long periods of little change are broken by shorter times of rapid selection

- natural selection and adaptation happens when a species is 'young'. by the time its distinctive features have evolved, the population is large enough to leave a fossil record

reproductive barriers

- ecological (ex. living in completely different habitats - water and land snakes)

- temporal (ex, breeding/blooming at different times - tulips and roses)

- behavioural (ex. distinct mating rituals attract specific mates - birds mating)

- mechanical (ex. part A must be compatible with part B - different sex organs that don't 'fit' together, like damsel flies)

- gametic (ex. gametes are incompatible - pollen from one flower can't fertilize another)

sexual selection

a form of natural selection in which individuals with certain traits are more likely to get a mate than others ex. peacocks with elaborate tails

speciation

the origin of new species (creates diversity)

stabilizing selection

individuals near the centre range of phenotype range have a higher fitness than individuals at either end of the range

allopatric speciation

speciation by geographic isolation - a species is split up physically and speciates into two different species

sympatric speciation

speciation by habitat isolation - exploiting a new niche may automatically reduce gene flow with individuals exploiting the other niche

hardy-weinburg equillibrium

frequencies of alleles in a gene pool are constant over time

1. must be random mating

2, large population

3. no movement in or out of the population

4. no mutations

5. no natural selection

sexual dimorphism

the stark contrasts between the phenotypes of females and males, which can be explained through sexual selection (ex. peacocks)

bateman's principle

sperm is cheap; eggs are rare

the operational sex ratio

the ratio of male to female individuals who are available for reproducing at any given time; females < males