populations, evolution, ecosystems

species

• group of similar organisms that can reproduce to give fertile offspring

population

• group of organisms of the same species in an area at a given time

gene pool

• range of alleles in a population

allelic frequency

• how often an allele occurs in a pooulation

what is the hardy weinberg principle

• preducts the allelic frequency won’t change from one generation to the next

• certain condtions:

  • large population

  • no immigration

  • no mutations

  • no natural selection

  • random sampling

what is the hardy weinberg equation

• p + q = 1

• p=frequency of dominant

• q= frequency of recessive

• p² + 2pq + q² = 1

• p²= homozygous dominant

• pq= heterozygous

• q²= homozygous recessive

causes of variation

• mutations

• crossing over and recombination

• independent segregation

• random fertilisation

• environemnt

stages of natural selection

• random mutation

• makes a new beneficial allele

• more likely to survive and repoduce

• pass on new allele to offspring

• allelic frequency of new allele increases

• better adapted for survival

evolution

• changes in allelic frequency over time

• natural selection

• variation due to different alleles

• slective pressures e.g iter/intracompetition

• some better adapted-survival of the fittest

• go on to reproduce

• pass of beneficial allele to offspring

• allelic frequency increases in gene pool

stabilising selection

• individuals with characteristucs nearer the middle of range are more likely to survive and reproduce

• bell shaped curve

• environment doesn’t change

dierectional selection

• individuals favouring one extreme more likely to survive and reproduce

• mean shifts

• environment changing

disrupting selection

• both extremes favoured

speciation

allopatric

sympatric

• development of a new species

• allopatric= requires geographical isolation- different selective pressures

• sympatric= random mutations make cells with differe number of chromosomes- can’t reproduce to mske fertile offspring

• genetic drift may lead to speciation

habitat

• where an organism lives

community

• organisms of different species in an area at a particular time

ecosystem

• all organisms and abiotic onditions in an area

abiotic

biotic

• abiotic= non-living

• biotic= living

niche

• how a species fits into an ecosystem- its role

adaptation

• feature that increases chance of survival

• physiological

• behavioural

• mechanical

INTERspecific competition

• different species

INTRAspecific competition

• same species

population size

• total number of organisms of a species in a habitat

carrying capacity

-maximum stable population size an ecosystem can support

random sampling

quadrats

• quadrat= metal grid

• split field into grids

• use random number generator to give coordintes

• place quadrat down

• count frequency/ % cover

• 20 repeats

random sampling

transects

• investigating environment factors on disribution

• tape measure on floor

• place quadray every 5 metres- top left corner at point every time

• take measurements

• repeat

• graph

mark release recapture

• used to measure population size assuming there is no deaths, no births, tag doesn’t harm animal

• get sample and tag them

• release

• recapture them

• total population= number caught in first sample X number caught in second sample divided by number of marked animals in sample 2

primary succession

• hostile abiotic conditons

• only pioneer species are adapted to grow there

• pioneer species die and microorganisms decmpose

• dead matter forms basic soil

• less hostile

• new species can grow

secondary succession

• larger plants colonise due to base layer

• these plants better adapted so outcompete organsims already there

• increased biodiversity

• climax community

• stays steady

conservation

• managing succession and protecting ecosystems

• techniques:

  • seedbanks- growing plants that are extinct in the wild

  • fishing quotas- limits amiunt of fishing of certain species

  • protected areas

  • breei]ding endangered species in captivity