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biology > 3.5 population size and ecosystems > Flashcards

3.5 population size and ecosystems Flashcards

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1
Q

define population

A

an interbreeding group of organisms of the same species occupying a particular habitat

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2
Q

define:
abiotic
community
ecosystem

A

non living/physical

all the living species in a habitat

interaction between living and non living components

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3
Q

what is succession?
give an example

A

changes over time in the species that occupy a particular area
e.g. when bare rock or barren land is first colonised

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4
Q

what is the pioneer community?

A

first species to colonise a habitat

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5
Q

what is the climax community?

A

last species to colonise a habitat (stable community which has reached equilibrium - no further succession)

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6
Q

what is sere?

A

a stage in succession

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7
Q

what is a dis climax/disruptive climax?

A

human interference that can affect the natural stages of succession

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8
Q

what are some examples of human interference that can affect the natural stages of succession?

A
  • grazing by sheep
  • deforestation
  • using land to grow crops
  • deliberate burning of heather moors to prevent a climax community stage (woodland) being reached
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9
Q

factors affecting succession (5)

A
  • migration
  • competition
  • facilitation
  • mutualism
  • commensalism
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10
Q

the immigration of what affects succession? (4)

A
  • spores (moss, fern, fungus)
  • seeds
  • animals
  • non-native species
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11
Q

what are the 2 types of competition? define them

A

intraspecific - same species
interspecific - different species (same niche)

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12
Q

what does niche mean?

A

the role and organism plays in a community

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13
Q

when can competition happen?
why does it happen?

A

at all seral stages. 2 species cannot occupy the same niche - the one with competitive advantages survive

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14
Q

what is facilitation?

A

allowing something to happen through positive interactions

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15
Q

how does facilitation benefit an ecological community?

A

provides better resource availability and refuge from physical stress, predation and competition

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16
Q

what does symbiosis broadly describe?

A

relationships between organisms

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17
Q

what is mutualism?
give an example

A

interaction benefiting both species
e.g. clown fish and sea anemone

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18
Q

what is commensalism?
give an example

A

one organism benefits and the other is unaffected. e.g cattle egret and cattle

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19
Q

what is a detritivore?
give an example

A

an organism which feeds on dead/ decaying organic matter e.g. earthworms

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20
Q

what is a saprotroph/saprobiont?
give an example

A

organism which discrete enzymes and perform digestion externally e.g fungi

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21
Q

what is nitrogen essential for?

A

protein synthesis

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22
Q

what conditions are needed for nitrification?

A

aerobic

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23
Q

what are the 4 main biological processes in the nitrogen cycle?

A

ammonification
nitrification
denitrification
nitrogen fixation

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24
Q

what happens during ammonification?

A

decomposers secrete enzymes that decay the dead plant and animal products

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25
Q

what happens during nitrification?

A

NH4+ (ammonium) from ammonification converted to nitrites then nitrates.

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26
Q

what are the 2 bacterias involved with nitrification?

A
  • nitrosomonas
  • nitrobacter
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27
Q

what happens during denitrification?

A

nitrates are converted to atmospheric nitrogen

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28
Q

what is the bacteria involved with denitrification?

A

pseudomonas

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29
Q

what happens during nitrogen fixation?

A

reduction of nitrogen to ammonium ions

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30
Q

what are the 2 bacterias involved with nitrogen fixation?

A
  • azotobacter (free-living in soil)
  • rhizobium (in root nodules of
    plants (legumes))
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31
Q

how is nitrogen taken up by plant roots?
(what form?)

A

as ammonium and nitrate ions by active transport and facilitated diffusion

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32
Q

once taken in by the roots, how does the plant use the nitrogen from the nitrate ions?

A

to synthesise:
- amino acids (to make proteins)
- nitrogenous bases (to make the nucleic acids RNA and DNA)
- chlorophyll

33
Q

what are some examples of human impact on the nitrogen cycle? (6)

A
  • soil aeration from ploughing
  • drainage
  • harder process
  • manure
  • slurry (manure + water)
  • fertilisers
34
Q

how do fertilisers reduce species diversity on grasslands? (2)

A
  • grasses and nettles grow well
  • shade out smaller plants
35
Q

how do fertilisers reduce species diversity in lakes? (2)

A
  • may result in eutrophication
  • leaching nitrates and phosphates adding to the natural process of salt build up
36
Q

explain eutrophication (5)

A
  • when it rains fertiliser runs into the lake
  • this leads to an increase in growth of algae and block the light from the plants
  • plants die and decomposers carry out decomposition
  • decomposers multiply
  • respiration of decomposers uses up oxygen so aquatic animals die due to lack of oxygen
37
Q

farmers need to abide by legislation to reduce nitrate leaching, give examples on how they do this? (3)

A
  • restrict amount of fertiliser on crops
  • only apply when crops readily growing
  • dig drainage ditches – eutrophication occurs here instead of natural water courses
38
Q

what is ecology?

A

the study of living things and their interactions with each other and their environment

39
Q

define habitat

A

a place in an ecosystem where an organism lives

40
Q

define niche

A

the role of an organism in an ecosystem, generally a feeding role

41
Q

what is the benefit to living in a population? (3)

A
  • more successful breeding and rearing of young
  • gaining protection from predators by living in groups - the group size effect
  • working as a group to locate new food sources
42
Q

what are the problems to living in a population? (2)

A
  • competition for resources like food and space
  • some individuals are better adapted than others and more likely to survive
43
Q

what are the factors causing a population size to increase? (2)

A
  • birth
  • immigration
44
Q

what are the factors causing a population to decrease? (2)

A
  • death
  • emigration
45
Q

how do plants emigrate?

A

via seed dispersal

46
Q

what is exponential growth?

A

when species colonising a new area have favourable conditions and the birth rate exceeds the death rate

47
Q

what is an equilibrium species?

A

the control of a species’ population is by competition in a stable habitat

48
Q

what graph is used to show an equilibrium species?

A

exponential J shaped curve

49
Q

what is an overshoot and what does it cause? (on a exponential J shaped curve)

A

the population growth exceeds carrying capacity
causes a die off in population

50
Q

what is an unstable equilibrium? (on an exponential J shaped curve)

A

the fluctuation of population above and below carrying capacity

51
Q

what is the cause of decreasing carrying capacity? (on an exponential J shaped curve)

A

resource destruction during an overshoot

52
Q

what is the carrying capacity?

A

the amount of organisms within a region that the environment can support sustainably

53
Q

what graph is used to show a fugitive species?

A

J-shaped curve

54
Q

what is a fugitive species’ strategy and why?
give an example of a fugitive species

A

to have high reproduction rates and disperse to increase their numbers as fugitive species are poor at competition
e.g. algae

55
Q

what are the 4 phases in the one step growth curve?

A

lag phase
log (exponential) phase
stationary phase
death phase

56
Q

explain the lag phase (3)

A
  • organisms adapt and prepare for growth
  • metabolic activity - enzyme synthesis
  • need to reach sexual maturity, find a mate and gestate
57
Q

explain the log phase (3)

A
  • happens as long as no factor limits growth
  • bacteria divide at a constant rate and population doubles
  • cannot grow indefinitely due to environmental resistance (food, space)
58
Q

explain the stationary phase (4)

A
  • birth rate = death rate
  • max size, reached carrying capacity for that environment
  • fluctuates in response to environmental changes
  • biotic factors in ‘normal environment’ e.g. predators will affect growth
59
Q

explain the death phase (2)

A
  • same factor as end of log phase
  • death rate greater than birth rate
60
Q

are biotic factors density - dependant or independent?
abiotic?

A

dependent
independent

61
Q

explain density dependent

A

affect a higher proportion of the population when more dense

62
Q

give an example of a density dependent biotic factor

A

food - depletion of food supply

63
Q

explain density independent

A

the effects of abiotic factors are the same regardless of the size of population

64
Q

what is negative feedback?

A

regulates population size. it’s a change in response to a first change to bring the numbers back to their original levels

65
Q

define abundance

A

the number of individuals in a species inna given area/volume

66
Q

how could you sample animals? (2)

A
  • capture - recapture (Lincolns index)
  • kick sampling in a stream
67
Q

how could you sample plants? (2)

A
  • quadrat - mean tubers of individuals, density
  • % cover
  • % frequency
68
Q

what does a belt transect provide?

A

abundance data

69
Q

what does a kite diagram show? (2)

A
  • the % cover of the species across a belt transect/across a set distance
  • show abundance and distribution of a species along a transect
70
Q

fill in the blank and define:
plants are ______ organisms

A

autotrophic - can produce its own food using light, water an carbon dioxide

71
Q

why does 60% of light that falls on a plant not get absorbed by photosynthetic pigments?
what happens as a result?

A

could be the wrong wavelength - can’t absorb green
therefore it is reflected or transmitted straight through the leaf

72
Q

what is photosynthetic efficiency (PE)?

A

the ability of a plant to absorb light energy (so it becomes part of the organic products of photosynthesis)

73
Q

what is the equation for photosynthetic efficiency?

A

PE = quantity of light energy incorporated into product ÷ quantity of light energy falling on the plant x100

74
Q

what range is PE usually between?

A

1-8%

75
Q

what is primary production?
what is primary productivity?

A

the production of new organic matter in plants (e.g. glucose)

the rate of production of new organic matter in plants.

76
Q

define GPP

A

the total amount of energy fixed inside new organic products in plants

77
Q

define NPP

A

the total amount of energy left in plants after respiratory losses are subtracted from the GPP - this is the energy in plants which is available to primary/first stage consumers in the ecosystem

78
Q

what is the equation for NPP?

A

GPP - respiration

79
Q

what is secondary productivity?

A

the rate of production of new organic matter/biomass in consumers

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