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biology > paper 2: Populations and Ecosystems > Flashcards

paper 2: Populations and Ecosystems Flashcards

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1
Q

define population

A

individuals of the same species occupying one area at one time that can potentially interbreed

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2
Q

define habitat

A

an area where an organism lives

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3
Q

define community

A

all the populations of all the species in one area at one time

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4
Q

define niche

A

the role an organism plays in the ecosystem and how it interacts with the biotic and abiotic factors

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5
Q

define biotic factor

A

a living factor which affects the distribution of an organism

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6
Q

define abiotic factor

A

a non-living factor which affects the distribution of an organism

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7
Q

define carrying capacity

A

the maximum population size of a species that an ecosystem can support

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8
Q

define ecosystem

A

consists of the community and the non-living components of its environment

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9
Q

explain why sampling should be carried out at random

A

to ensure that all data collected is not biased

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10
Q

describe how you would retrieve reliable and representative data when sampling

A

you must take a large sample

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11
Q

define interspecific competition

A

competition between different species

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12
Q

define intraspecific competition

A

competition between the same species

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13
Q

define predation

A

how the populations of predators and prey affect each other

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14
Q

describe intraspecific competition

A
  • members of the same species compete for the same resources e.g. food
  • if population gets too big then intraspecific competition increases so population falls again
  • if population gets too small, intraspecific decreases so population size increases again
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15
Q

draw and label a graph showing intraspecific competition

A
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16
Q

describe interspecific competition

A

one species will outcompete the other one if they occupy the same niche

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17
Q

draw a graph showing interspecific competition

A
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18
Q

explain predation

A
  • prey population increase so food source increases for the predator so predator population increases shortly after
  • more predators so more prey are killed so prey population decreases
  • less prey to eat so predator population decreases because they die of starvation
  • less prey eaten so prey population increases and the cycle starts again
19
Q

draw a graph showing predation

A
20
Q

why is there a delay in time between increase prey population and increased predator population

A

give time for reproduction of predators

21
Q

why must a sample be random

A

prevent bias

22
Q

why must a sample be large

A
  • sample is more representative
  • calculate more reliable mean
  • allows use of stats test
23
Q

what are quadrats used for

A

estimate size of population of a particular species in a certain area

24
Q

describe the step-by-step method of random sampling with quadrats

A
  1. split area into a grid and asign coordinates
  2. pick coordinates randomly using a random number table
  3. place quadrat at coordinates and count number of individuals or % cover
  4. repeat a large number of times and calculate a mean
  5. multiply this mean by the number of times the quadrat fits ino the area
25
Q

for sample seaweed with a quadrat, explain which method you would use

A

% cover
less time consuming than counting individual plants / cannot identify individual plants/ too many individuals

26
Q

how can you find the correct number of quadrats to use to get representative data

A

calculate a running mean until the mean stays constant

27
Q

what are transects used to show

A

show chnages down an environmental gradient

28
Q

what is a limitation of using transects

A

single transect might not go through a representative data

29
Q

how would you make sure that you have a representative sample of the area when using transects

A
  • select position of transects at random
  • use a large number of parallel transects and calculate the mean at each distance
30
Q

decsribe the step-by-step method of using a transect

A
  1. several belt transects are placed at parallel across an area and numbered
  2. a transect is chosen at random using a random number generator button on a calculator
  3. a quadrat is placed along the line at regular intervals
  4. the % cover or number of each species are counted in each quadrat
  5. this is repeated across a large number of parallel transects and a mean at each interval
31
Q

what is the mark, release, recapture method used for

A

used to estimate the sizes of populations of motile organisms

32
Q

equation for mark, release, recapture

A
33
Q

equation for mark, release, recapture

A
34
Q

what are the assumptions made with the mark, release, recapture method

A
  • birth rate = death rate
  • marking does not influence survival such as increasing chances of predation and is non-toxic
  • no immigration/ emmigration
  • long enough time for marked individuals to evenly distribute into the population between release and recapture
35
Q

describe the stages of succession

A
  1. starts with colonisation of pioneer species in hostile conditions
  2. pioneer species change abiotic conditions e.g. from soil/ humus
  3. environment becomes less hostile and more suitable for new species to colonise
  4. new species out-compete the pioneer species so pioneer number decrease
  5. from stage to stage, genetic diversity increases
  6. eventually a climax community is reached
36
Q

what does primary siccession start with

A

bare rock or sand

37
Q

what does secondary succession start with

A

soil and some vegetation

38
Q

what is the ecosystem like in a climax community

A
  • stable populations
  • abiotic conditions are constant
  • same species are present
39
Q

explain why species diversity may decrease slightly in a climax community

A
  • trees block light reaching the ground, so less photosynthesis
  • only plants which can photosynthesise at low light intensities survive
40
Q

what is turbidity

A

a measure of how much solid is in a solution

41
Q

what piece of equipment measures turbidity

A

spectrophotometer

42
Q

how does a spectrophotometer measure turbidity

A
  • light passed through the solution
  • absorbance is measured
  • the more turbid the solution the more light is absorbed
43
Q

why is a log scale used when measuring turbidity

A

when there is a large range of numbers

biology (30 decks)

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