3.4.1 aqa bio4 populations

a mindmap on everything i can think of related to the populations topic in a2 unit 4 aqa biology. its 3.4.1 on  specification

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  • Created by: minnie me
  • Created on: 18-12-12 10:19
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  • Populations and Ecosystem  the facts
    • Measuring Biotic factors
    • Definitions
      • community: all the organisms of all the species in a habitat
      • population: all the  organisms of one species in a habitat
      • birth rate: births per thousands and per year
    • Mark- recapture method
      • TM1xTM2 / M2  = size of population
      • conditions:  population is stable no birth/ deaths no immigration/ emigration
      • the  size of the population may change  due to organisms leaving, also the formation of seperate  territories for breeding. as possibly a certain territory may be captued twice and marked
      • they could  capture a sample of individuals using a suitable trap  and then mark the  individuals  so they are recognizable but not harmed count and then release after a period of time (to allow them to redistribute evenly throughout the total population)  capture a second sample  count total and marked individuals  now population size can be estiestimated
      • the base sequence acts as a mark so the whales don't need to be marked and when recaptured the base sequences can be checked against a known database to see if same has been captured before
    • Varation in population size
      • predation, interspecific, intraspecific competition
        • when the prey population is high there is lots of food for the predators so their population rises after a time lag, this now large predator population consumes more prey thus its population reduces food supply reduces for predator  its population reduces
          • the sudden decrease in stikleback(predator) population, results in the population of fresh water shrimps to increase as they have fewer predator, the large population of freshwater shrimps consume more   singlecelled producer, thus reducing the food supply to the mayfly larva so its population decreases
        • feather mites reduce the amount of oil the birds produce so their feathers are in poor condition and breeding is reduced
        • as the number of newts increase the percentage survival of the spadefoot toad tadpoles decrease, also the southern toad tadpoles decrease
          • an increase in the number of newts, Increases the number of spring peeper frogs, this may be because newts reduce competition of the frogs for food so food supply Increases
          • as the percentage survival of the tadpoles decreases re are fewer tadpoles in the  pond so competition for food is reduced the few toads that have survived have more food so increase in mass
        • advantage of different niches is  that there is less competition for food due to the competitive exulsion principle
    • Sampling
      • Sampling Plants
        • distribution of marram grass: using a line transect. a line  measuring from one side of the dune to the other, at regular intervals of the line place a quadrat within eaxh quadrat count the number of marram grass
      • Sampling Animals
        • sampled at random to ensure results are not bias and the data is representative and enough for statistical test. random using generator and grid
          • using 10 quadrats is unreliable as the total number of species is still increasing after 10 quadrats. also using 25 quadrats will waste time as total number of species remains constant as graph flattens
      • human disturbance: more people cause the seaweed to damage so few are left to survive and grow larger. also the larger animals are affected by humans so more smaller animals survive (they are younger) also there are fewer seaweed  so fewer niches. also changing land use removes variety of food for animals so animal variety reduces
    • adaptation to abiotic and biotic factors
      • large sized snow geese are adapted to breeding in colder condtions: a large snow geese has a small surface area to volume ratio, however the geese have more fat which provides and maintains insulation thus maintaininga regular body temperature
      • each  species has an adaptation to its niche such as a different shaped mouth     as each species may have a different feeding method, or food ssource may be found in only certain places. adaptations reduce competition.
    • Measuring Abiotic factors ( non living component of a niche)
      • temperature light intensity
      • as temperature changes the white geese become less camouflaged
    • human populations
      • average life expectancy: the age when 50% of the population is still alive         curve A undeveloped   curve B developing curve C developed
      • why curve A decreasing shape: because its survival curve of an undeveloped country, which suffers from poor sanitation and medical care as curve drops steeply
      • stable population = (b+e) - (d+i)     increasing population = (b+e) - (d+i) >1  population growth = (b+i) -(d+e)
        • percentage growth rate = population change during  period x100/ population at start of period
  • population: all the  organisms of one species in a habitat
  • Measuring Abiotic factors ( non living component of a niche)
    • temperature light intensity
    • as temperature changes the white geese become less camouflaged
  • why curve A decreasing shape: because its survival curve of an undeveloped country, which suffers from poor sanitation and medical care as curve drops steeply

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