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A-level Biology > Chapter 19 - Populations in ecosystems > Flashcards

Chapter 19 - Populations in ecosystems Flashcards

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1
Q

what is ecology

A

studying the inter relationships between organisms and their environment

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2
Q

what are abiotic factors

A

non living

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3
Q

what are biotic factors

A

living

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4
Q

what are the two major processes to consider in an ecosystem

A

the flow of energy

the recycling of elements

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5
Q

what is a population

A

a group of individuals go one species that occupy the same habitat and have the potential to interbreed

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6
Q

what is carrying capacity

A

the size of a population an ecosystem can support

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7
Q

what is a community

A

different populations living and interacting in the same area at the same time

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8
Q

what is a habitat

A

the place where an organism usually lives

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9
Q

what are microhabitats

A

smaller units within a larger habitat each with its own microclimate

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10
Q

what is a niche

A

how an organism fits into its environment

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11
Q

what are adaptations

A

features that increase the chances of a species surviving and reproducing

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12
Q

what is population size

A

the number of individuals in a population

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13
Q

give two reasons why a population may fluctuate

A

the effect of abiotic factors

interaction between organisms

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14
Q

in what instance is it useful to use a logarithmic scale

A

where the population grows rapidly over a short period of time

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15
Q

how does a logarithmic scale differ from a normal one

A

log (population) is plotted rather than the population itself

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16
Q

give three reasons why a population may start to level out

A

consuming and using up mineral ions
winter brings lower temperature and levels of light intensity
bacteria collect at the surface and prevent light reaching those at the bottom

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17
Q

what are the 4 abiotic factors that influence the size of a population

A

temperature
ph
light intensity
water and humidity

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18
Q

how does temperature influence population size

A

enzymes to low means theres less kinetic energy for successful collisions and too high denatures the enzyme
warm blooded organisms have to expend energy in maintaining their temp levels

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19
Q

how does light influences population size

A

photosynthesis - more light means more photosynthesis

this increases their carrying capacity so more aninals can survive

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20
Q

how does water/humidity impact population size

A

too dry means that more evaporation occurs so there is no growth or food produced ]
too wet means that special adaptations are required to survive and so diversity is reduced

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21
Q

what are the two types of competition

A

interspecific and intraspecific

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22
Q

what is infraspecific

A

individuals of the same species competing for resources

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23
Q

how does intrapspeicfic competition impact a population

A

the availability of resources determines the carrying capacity and so population size

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24
Q

what is interspeicifc competition

A

individuals of different species competing for resources

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25
Q

how does interspecific competition impact a population

A

because the two species are occupying the same niche, one will have a competitive advantage over the other. this population will grow whilst the other will shrink and finally disappear

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26
Q

what is the competitive exclusion principle

A

where there are two species occupying the same niche, one will normally have a competitive advantage
the population of this species will grow and the population of the other will diminish
conditions remain the same leading to the removal of one species

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27
Q

when are you explaining how a factor influences population size what is it important to link your explanation to

A

the birth/death rate

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28
Q

what is predation

A

one organism consuming another

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29
Q

why is data gathered on predation in a lab generally not representative

A

the prey is usually exterminated by predators
this is because the size and type of habitat available is much less varied and smaller than in nature
there are also many more refuges in nature so although the prey population may fall to a low level, it rarely becomes extinct

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30
Q

what effect do predators and prey have upon eachothr

A

predators eat prey , reducing the prey population
the predators are in greater competition with each other for the prey that remains
the predator population then falls as there isn’t enough food to support a larger population
fewer prey are eaten and so reproduce to rebuild their population
the predator population increases as there is more food sources

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31
Q

why is the graph showing predator prey cycles normally exaggerated

A

in natural ecosystems predators normally eat a range of prey rather than just one species

32
Q

What other factors can influence a population

A

disease and climate

33
Q

why is the cyclical relationship of predators and prey important

A

the crashes in populations are important in evolution as they create selection pressures and only those adapted to the conditions can survive

34
Q

what is abundance

A

the number of individuals in a specific area

35
Q

what are the two types of sampling we use

A

random and systematic

36
Q

what are the two types of quadrat

A

a point quadrat and a frame quadrat

37
Q

what is a point quadrat

A

a horizontal bar supported by two legs. there are hokes along the length of the bar through which a pin is place. the species touching the pin is then recorded

38
Q

what is a frame quadrat

A

a square frame divided into equal subdivisions

39
Q

what are the three factors to consider when using quadrats

A

the size of the quadrat to use
the number of quadrat samples to conduct
the position of each quadrat in the study area

40
Q

why is it important to consider the size of quadrats used

A

the size must be appropriate to the size of the area being studied
to get a representative sample, it is normally better to use a larger number of smaller quadrats

41
Q

why is it important to consider the number of quadrats used

A

the greater the number of quadrats used the more reliable and representative your results will be. however this is a time consuming process

42
Q

why is it important to consider the positioning of each quadrat

A

random sampling must be used to avoid bias and make your results reliable

43
Q

how do you conduct a random sample of an area

A

lay two long tape measures at right angles to each other
use a random number generator to generate your coordinates
place to quadrat at the intersection of these coordinates and record the species inside it

44
Q

how do you conduct systematic sampling of an area

A

lay out a long piece of strong across the area you wish too study
lay down a frame quadrat at the beginning of the strong
record the species inside the quadrat
move the quadrat its own distance down the string and repeat the process

45
Q

what is abundance

A

the number of a species in a given area

46
Q

what are the two common measures of abundance we use

A

frequency and percentage cover

47
Q

when is percentage cover useful

A

when a species is particularly abundant or difficult to count. this is because the species don’t need to be counted individually and can be conducted fairly quickly

48
Q

what is percentage cover

A

an estimate of the area within a quadrat that a particular species occupies

49
Q

what is frequency

A

the likelihood of a. species appearing in a quadrat

50
Q

when is frequency useful

A

it is quick and gives information about the general area of a species particularly when it is difficult to count

51
Q

when is calculating frequency not useful

A

it doesn’t provide information on the density of a species or its positioning

52
Q

when are transects and quadrats not useful

A

for mobile animals

53
Q

what method is used to calculate the abundance of aniamsl

A

mark
release
recapture

54
Q

what is the equation for mark release recapture

A

population size = total no of individuals in 1st sample x total no in the 2nd sample / no of marked individuals recaptured

55
Q

what are the size assumptions made for mark release recapture

A
  • mark is not rubbed off
  • few deaths and births within the pop
  • method or marking isn’t toxic or marks animal more susceptible to predators
  • no emigration or immigration
  • the mark individuals have sufficient time to redistribute themselves throughout the population
  • the proportion of marked- unmarked individuals in the second sample is the same as the proportion of marked : unmarked in the total population
56
Q

what is conservation

A

managing the earths natural soreuces by humans in such a way that maximum use of them can be made in the future

57
Q

what does conservation aim to preserve

A

ecosystem and biodiversity

58
Q

what are the four main reasons for conservation

A

personal ethical economic and cultural aesthetic

59
Q

why do we conserve the plant for personal reasons

A

we are supporting out life system

60
Q

why do we conserve the plant for economic reasons

A

the organism we conserve have a huge pool of genes which enable the plants to make many of th eusbstances we use and profit form all the time

61
Q

why do we conserve the planet for ethical reasons

A

we should respect the living organisms that have been on earth longer than us

62
Q

why do we conserve the planet for cultural reasons

A

the variety of organisms that have been on earth longer than us

63
Q

why might a pioneer species not feature in a climax community

A

their habitats have disappeared because of succession or the have been out competed

64
Q

how do we conserve the planet by managing succession

A

we put factors in place to prevent further succession and so removal of habitats

65
Q

what is succession

A

the changes that occur to a particular ecosystem over time

66
Q

what is primary succession

A

occurs on land that has just been formed or exposed- there is no soil or organic material to start with

67
Q

what is seoncdary succession

A

occurs on land that has been cleared by humans but soil and organic material remains

68
Q

which type of succession is faster and why

A

secondary succession there is already some existing organic matter and soil so different species can be supported

69
Q

what is important to remember when considering succession

A

competition

70
Q

what is a pioneer species

A

a species that is adapted to living in extreme conditions and cans tart to colonise an area

71
Q

what are some of the adaptations that a pioneer species might have

A

asxueal reproduction
rapid germination of seeds
tolerance of extreme conditions
ability to photosynthesis and grow own food

72
Q

describe succession

A
  • pioneer species- the first species to colonise an area have adaptations to withstand extreme conditions
  • pioneer species penetrates and breaks up the rock, as the species dies and decomposes a layer of humus builds up allowing simple plants to grow
  • these plants cast shade, preventing the pioneer species from growing. they have longer roots and so can break up men more rock. as they die the amount of nutrients and water in the soil increases so more complex plants can be supported
  • larger plants grow so animals can inhabit them. this changes the soil and light conditions , linking the smaller plants
  • a climax community Is reached and dominant plant species colonise an area
73
Q

what is the most common climax in the uk

A

oak woodland

74
Q

how to calculate the mean density

A

total no of individuals counted / total no of quadrats x area of one quadrat

75
Q

what are the two factors that impact the succession of animals

A

habitats and food sources

76
Q

how does succession in animals occur

A

over time, more complex animals can be supported by organic matter
this means that there are more food sources and larger animals come to the area

77
Q

what five features emerge during succession

A 
the abiotic environment becomes less hostile 
more habitats and niches 
increased biodiversity 
more complex food webs
increased biomass

A-level Biology (19 decks)

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