topic 7 Flashcards
what is a population
group of organisms of the same species living in a particular area at a particular time that can potenttially interbreed.
what is a gene pool
range of alleles in a population
what is allele frequency
how often allele occurs in a population
what is the hardy-weinberg principle
predicts the frequency of alleles in a population that wont change from one generation to the next
what do the conditions of hardy weinberg apply to
- large population
- no immigration
- no mutations
- no natural selection
no emigration
what does the p stand for in hardy weinberg
dominant allele
what does the q stand forr in hardy weinberg
the recessive allele
why might individulas within a population show a wide range of variation in a phenotype. (5 things)
-mutations
-random fertilisation
-independat segragation of homologus chromosomes
- crossing over
- environmental factors
what is evolution
a change in allele frequency over time
what way does evolution occur
natural selection
describe the process of natural selection
Evolution: change in allele frequencies in a population over time
1. Variation within a population due to mutations
2. Selection pressure e.g. predation, disease, competition à struggle for survival
3. Some organisms have phenotypes providing selective advantages (due to favourable allele(s))
4. These organisms are more likely to survive and reproduce, producing more offspring and
passing on their favourable allele(s) to the next generation i.e. differential levels of survival and
reproductive success
what do organisms need to fight for *******
-predation
- disease
- competiton
what is stabilising selection
- selective pressure favours the mean phenotype
- individuals with the extreme phenotype are less likely to survive and reproduce.
- occurs in an unchanging environment
what is directional selection
- selective pressure acts on the extreme phenotype.
- so they are more likely to survive and reproduce.
- due to a response to a change in the environment.
what is disruptive selection
when both the extreme phenotypes are favoured .
this can result in two different species.
environment favours both the extreme phenotypes
what are the two types of speciation
allopatric speciaiton
symptatric specition
what is speciation
the development of a new species from an existing speces
what happens to the population during speciation
they are reproductively isolated
how do new species arise
when members of a population are unable to interbreed to produce fertile offsprings
what type of isolation occurs in allopatric speciation
geographic isolation
what are examples that may cause geographic isolation
flooding
earthquake
what do physical barrieers prevent in allopatric speciation
inerbreeding between species
describe allopatric speciation
- a population is geographically isolated and so are therfore reproductively isolated.
- mutations causes genetic variation in each population
- there are different selection pressures that acts on each population.
- natural selection on favourable alleles.
- alleleic frequency increases over time
-memebers of the samee population cant inteerbreeed to produce fertile offsprings
what is sympatric speciation
when the populations arent gentically isolated
how does sympatric speciation occur
genetic variation due to mutations preventing membeers from of tthat population from breeding
where can the mutations occur in sympatric speciation
in the chromosome number
what are the different mechanisms that make individuals reproductively isolated
- seasonal
- mechanical
- behavioural
temporal/ seasonal
different mating/ breeding seasons
mechanical
changes in genitalia which prevents successful mating
behavioural
different courtship behaviour preventing mating
what is genetic drift
when allele frequency of a popoulation changes over generations due to chance
what other factor affects natural selection
genetic drift
what is the founder effect
when smaller colonies forms from a larger one.
what is a community
a population of diffferent species
what is an ecosystem
a community plus all the non living components
what is a niche
the role of a species within its habitat
like what it eats and where it feeds
what are aibiotic conditions
non living components of an ecosystem
what are biotic conditions
the living features of an ecosystem
what is the carrying capacity
the maxiumum stable population an ecosysteem can support
how can population size vary as a result of intercations between organisms
competition
aibiotic factors
predation
what is interspecific competition
competition between organisms of dfferent species.
what happens in interspecific competition
it reduces resources avaliable to both species
when one species is better adapted it will out-compete the others
what is intraspecific competition
competition between organisms of the same species
what does a small population mean in terms of copetition
results in less competition
what is predation
when an organism kills and eats another organism
increased predator population size à more prey eaten à prey population falls à less
food for predators à predator population size falls à prey population rises à predator
population rises again…
increased predator population size à more prey eaten à prey population falls à less
food for predators à predator population size falls à prey population rises à predator
population rises again…
what is succession
process by which an ecosystem changes overtime
what is a pioneer species
the first species to colonise
what do pioneer species do
they change the aibiotic consitions so that the environment is less hostile
- which allows the environment to be more sutibale for other speciees with different species
what happens to the biodiversity as succesion goes on
it increases
what is the climax community
the final, complex, stable community
why are pioneer species able to grow in aibiotic conditions
they are better adapted
how do thee pioneer species change the aibiotic conditions
they die and microorganisms decompose dead matter to humus
in order to form basic soil
what is secondary succesion
when land has been cleared
e.g a fire
what is primary succession
land that has been newly formed or exposed
what is plagioclimax
when succession is stoppedd artifically by human activity so stops a climax community from forming.
how can you manage succession
conservation
what is the purpose of conservation
in order to preserve the community in its current stage of succesion
what is conservation
protection and management of species and habitats in a sustainable way
