Evolution SJ Flashcards
name 2 things that are evidence for evolution?
1) diversity
2) adaptation
what are homologous characters?
traits inherited from a common ancestor but may now serve different functions
define gene frequency
proportional representation of a gene in the population
3 rules of mendelian inheritance
1) heredity is not blending
2) acquired characters are not inherited
3) it does not produce a change in gene frequency
what is the hardy Weinburg equilibrium?
gene frequency in a population that is not evolving - no change in gene frequency
5 conditions for hardy weinburg
1) infinite population size with no genetic drift
2) no mutation
3) mendelian inheritence
4) no selection
5) random mating
what is sexual selection?
traits which favour males/females getting mates e.g attractiveness traits
definition of adaptation
evolutionary change that fits an organism to its habitat
3 factors necessary for selection
1) multiplication - struggle for existence
2) variation
3) inheritence
what are discontinuous characters?
determined by one set of genes - distributions don’t overlap
what are continuous characters?
determined by multiple genes
define neodarwinism
natural selection + mendelian inheritence
What is directional selection?
the mean value moves
what is stabilising selection?
the variation is reduced and the mean value stays the same
what is disruptive selection?
no intermediate - two distinct groups
describe batsman mimicry
certain organisms mimic the look of others which have feature to defend against predators e.g. wasps have stings so predators learn to stay away so others without this ability mimic the look or wasps
what is temporal environmental variation?
change in weather conditions causing organisms to adapt
define fitness
genetic contribution to subsequent generations
how can fitness be measured
as lifetime reproductive sucess
what is intrasexual selection?
between a gender e.g. males stronger to fight other males
what is inter sexual selection?
between the genders - males attracting females by good genes and access to resources
what is polyandry?
when a female has many sexual partners
what is monogamy?
one partner no sexual dimorphism
what is polygamy?
when males and females have multiple sexual partners - sexual dimorphism
what is polygyny?
when a male has many sexual partners
describe altruistic behaviour?
behaviour which benefits other individuals at a cost to the altruistic individual
the rate of individual selection is determined by…
the length of a generation
the rate of group selection is determined by…
the length of a groups generation
how did altruism evolve?
it is selfish at the level of the gene - altruistic individuals help other altruistic individuals so the altruistic gene continues in population
what is hamiltons rule?
rb>C
what is kin selection?
where helping kins breed has same genetic output as breeding itself
what is micro evolution?
changes within a species
what is speciation?
splitting one species into two
explain gene flow
exchange of genes between populations as a result of movement and interbreeding of individuals
what are 2 theories of speciation?
1) divergence - species adapt to different environments
2) reproductive isolation - populations can’t interbreed
what is allopatric speciation?
isolation then divergence - environmental change causing different selection pressures
what is sympatric speciation?
divergence then isolation - disruptive selection outweighs the effect of gene flow
what is gradualism?
natural selection acting on a species to produce a gradual change in a species until speciation occurs
an example of a good fossil record?
solenhofen limestone - lake with no oxygen so bodies didn’t decompose
what is divergent evolution?
when lineages split and separate but share a common ancestor
what is convergent evolution?
not closely related species all exploiting similar resources
what is adaptive radiation?
the evolution of character that allow exploitation of a new habitat
what is mass extinction?
a period of geological time when extinction rate peaks
what is local extinction?
loss of a population from a particular geographical area
describe racial senescence
species undergo a lifecycle like individuals , orthogenesis- variation follows a particular direction
3 reasons that may explain why species have gone extinct
1) racial senescence
2) competition from better adapted species
3) environmental change
what are the 5 mass extinctions?
1) ordovician - marine invertebrates
2) devonian - marine invertebrates and fish
3) permian - marine invertebrates, trilobites , reptiles
4) triassic - marine invertebrates, freshwater fish, reptiles, insects
5) cretaceous - marine invertebrates, ammonites, marsupials, belemnites, plesiosaurs, Mosasaurs, Pterosaurs, Dinosaurs
describe the cretaceous extinction and evidence for it
asteroid impact - KT boundary where fossils of dinosaurs are no longer found
describe a selfish gene
anything that a gene can do to favour its own spread at the expense of others will be favoured by selection
altruism is only favoured by evolution if…
it increases rate of spread of a gene
describe dawkins green beard selection example
where altruistic genes are linked to an obvious phenotype so individuals act altruistically towards others with the same phenotype trait - doesn’t require relatedness
what is cooperative behaviour?
individuals cooperate for their own selfish reasons
cooperation only evolves when…
the behaviour causes it to spread faster and increase the fitness of an individual
what are 3 human acts causing extinction?
1) hunting
2) introduction of alien species
3) habitat loss by human activities e.g. logging
what is phylogenetic niche conservatism?
species inherit their niches from their ancestors
what is phylogenetic diversity?
the total amount of evolutionary history shared by a group of species
which species are best to try and conserve from extinction?
- broad phylogenetic diversity because more closely related species share similar extinction risks
- evolutionary distinct species to save them
