topic 7
Cards (7)
- suggest and explain how allopatric speciation occurs.
- random mutations cause variation
- different habitats have different environmental conditions
- gene pools are kept separate/ reproductively isolated
- change in allele frequencies as different alleles are passed on
- cannot interbreed to produce fertile offspring
- Loss of nutrients into Lake Malawi has resulted ina decrease in some fish populations. Explain why.eutrophication
- increase growth of algae (algal bloom) blocks sunlight
- plants cannot photosynthesise so they die
- saprobionts aerobically repsire so use up oxygen
- less oxygen for fish to aerobically respire so they die
- The mark-release-recapture method can be used to estimate the size of the population. Explain how.
- capture sample one, mark and release
- ensure marking is not harmful (does not affect survival/courtship)
- allow sufficient time for the population to randomly distribute before collecting the second sample
- population size = sample 1 x sample 2 / marked recaptured
- suggest why the mark-release-recapture method can produce unreliable results in large areas.
- less chance of recaturing fish
- unlikely that fish will distriute evenly / randomly
- describe and explain how succession occurs
- colonisation of hostile environment by pioneer species
- pioneer change environmental consitions eg. top soil
- environment becomes less histile for new species to grow
- change / increase in biodiversity
- larger species outcompete smaller to cilmax community
- describe how you could estimate the size of a population of small plants in an area
- use a grid
- randomly generate a set of coordinates
- count abundance / percentage cover in each quadrat (1m2)
- use a large sample size and calculate the mean
- multiply mean in 1m2 by total area
- Give two features of a climax community
- same species present over long time (stable community)
- abiotic factors stay constant
- populations stable (around carrying capacity)