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WJEC Biology A-Level > Unit 3.5 PopulationSize & Ecosystems (physics&mathstutorflashcards)) > Flashcards

Unit 3.5 PopulationSize & Ecosystems (physics&mathstutorflashcards))

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1
Q

population

A

number of individuals (of the same species) within a given area

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2
Q

community

A

2 or more populations of (different) species within an ecosystem

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3
Q

habitat

A

the physical environment where a particular community of a population lives

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4
Q

environment

A

conditions that surround an organism (biotic+abiotic)

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5
Q

biotic

A

any living factor which affects another organism/species in any way

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6
Q

abiotic

A

non living part of the environment that can affect organisms (chemical+physical)

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7
Q

name 4 biotic factors

A
  • food competition/availability
  • disease
  • resource/habitat competition
  • predation
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8
Q

name 6 abiotic factors

A
  • light intensity
  • temperature
  • pH
  • wind+moisture
  • salinity
    -CO2/O2 conc
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9
Q

ecosystem

A

a dynamic biological community that is made up of biotic+abiotic components

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10
Q

niche

A

role of an organism in the ecosystem (prey/preditor)

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11
Q

dispersion

A

how geographically spaced out organisms are

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12
Q

fecundity

A

number of offspring an individual can have in a lifetime

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13
Q

name 4 limiting factors

A
  • food
  • temperature
  • mates
  • space
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14
Q

carrying capacity

A

number of individuals a habitat can sustain

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15
Q

growth rate =

A

(births - death)/original pop size

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16
Q

what factors alter density

A

births/deaths and immigration/emigration

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17
Q

density-dependant

A

effects on population size differ with population density
(larger pop = larger death rate)

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18
Q

density-independent

A

not influenced by a species population size

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19
Q

define ecology

A

the study of the relationships among organisms and their environments

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20
Q

what is a large ecosystem called

A

biome

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21
Q

what is a small ecosystem called

A

microhabitat

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22
Q

what do population numbers depend on

A

births/deaths and immigration/emigration

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23
Q

define birth rate

A

the number of offspring born per thousand of population per year

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24
Q

define death rate

A

the number of deaths per thousand of population per year

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25
Q

what is immigration

A

the number of individuals entering a region per thousand of population per year

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26
Q

what is emigration

A

the number of individuals leaving a region per thousand of population per year

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27
Q

when do population sizes increase

A

when
births + immigrants > death + emigrants

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28
Q

when do population sizes decrease

A

when
births + immigrants < death + emigrants

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29
Q

what are the 3 phases of population growth

A
  • lag phase
  • log phase
  • stationary phase
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30
Q

define the Lag phase of population growth

A

period of slow population growth

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31
Q

define the Log phase of population growth

A

period of rapid exponential population growth in which birth rate > death rate

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32
Q

define the Stationary phase of population growth

A

period of stability in which population numbers generally remain constant

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33
Q

what are the axis on a graph showing bacterial population growth

A

side = Log of number of cells
bottom = time (hours)

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34
Q

what causes the carrying capacity to vary

A

biotic + abiotic factors

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35
Q

what is competition

A

when different organisms compete for the same resources in an ecosystem

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36
Q

give 3 examples of density-dependant factors

A
  • competition
  • predation
  • disease
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37
Q

give an example of density-independant factors

A
  • climate
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38
Q

define distribution

A

The spread of living organisms in an ecosystem

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39
Q

what is sampling

A

selecting a group of individuals that will represent the whole target population

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40
Q

what does sampling allow us to do

A

allows us to measure the distribution and abundance of organisms

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41
Q

suggest 2 methods of assessing abundance and distribution of organisms

A
  1. quadrats
  2. transects
42
Q

what is a quadrat

A

square frames which are placed at random in an area to be investigated

43
Q

what is a transect

A

a line/belt that runs across the area to be investigated

44
Q

suggest 3 different ways that abundance can be measured

A
  • % area cover
  • % frequence
  • density
45
Q

what is random sampling

A

a sampling technique used to avoid bias

(e.g creating a square grid and generating random coordinates)

46
Q

what is systematic sampling

A

sampling technique used to determine the abundance and distribution of organisms along an area at periodic intervals
(e.g along a belt transect)

47
Q

what is the source of energy for an ecosystem

A

light energy

48
Q

when is light not the source of energy for an ecosystem

A

when ecosystems rely on chemosynthesis

49
Q

what is a trophic level

A

the position that an organism holds in a:
- food chain
- food web
- pyramid of numbers
- pyramid of biomass

50
Q

what is biomass

A

the total dry mass of tissue

51
Q

state the formula for efficiency of biomass transfer

A

efficiency = (biomass transferred / biomass intake) x100

52
Q

why is some energy never taken in at each trophic level

A
  • some parts of food are not consumed
  • some parts of food are not digestible
  • plants can not use all light energy as some is the wrong wavelength
53
Q

why is some energy lost at each trophic level

A

respiration = lost as heat

54
Q

what is a pyramid of biomass

A

a table of the dry mass of living material at each trophic level of a food chain

55
Q

define gross primary productivity (GPP)

A

the chemical energy stored in plant biomass (made during photosynthesis)
measured in kJ m⁻² year⁻¹

56
Q

define net primary productivity (NPP)

A

the amount of chemical energy that is available to heterotrophs in an ecosystem

57
Q

how is NPP calculated

A

NPP = GPP - Respiration losses

58
Q

define primary succession

A

where an area previously devoid of life is colonised by pioneer species

59
Q

what is a pioneer species

A

species that can survive in hostile environments and colonise bare rock or sand

60
Q

summarise the process of primary succession

A
  1. pioneer species colonise the area
  2. pioneer species die + decompose = nutrients are added to ground
  3. over time, this allows more complex organisms to survive
61
Q

what are seres

A

various intermediate stages in succession in an ecosystem progressing towards a climax community

62
Q

define secondary succession

A

a type of succession in which a habitat is re-colonised after a disturbance

63
Q

what is a climax community

A

the final stage of succession, where the ecosystem is balanced and stable

64
Q

how can you tell that the climax community has been reached

A

soil is rich enough to support large trees/shrubs and the environment is no longer changing

65
Q

how does succession affect species diversity and stability of the community

A

succession INCREASES species diversity and the stability of the community

66
Q

which 2 organisms play an important role in decay

A
  • detritivores
  • saprotrophs
67
Q

what does a detritivore feed on

A

dead and organic matter

68
Q

what does a saprotroph feed on

A

feeds by extracellular digestion

69
Q

describe extracellular digestion by saprotrophs

A

release enzymes which catalyse breakdown of dead plant and animal material into simpler organic matter

70
Q

what is the carbon cycle

A

when carbon (in form of CO₂) moves between living organisms and the environment.
involving:
- respiration
- photosynthesis
- combustion

71
Q

describe the 5 stages of the carbon cycle

A
  1. plants remove CO₂ from atmosphere via photosynthesis
  2. eating passes carbon compounds along food chain
  3. respiration returns CO₂ into atmosphere
  4. organisms die + decompose.
    saprotrophs break down dead material and release CO₂ via respiration
  5. Combustion of materials (wood, fossil fuels) release CO₂
72
Q

define global warming

A

the gradual rise in the average temperature of the earth due to increasing atmospheric levels of CO₂ + methane gas

73
Q

define the greenhouse effect

A

the increase of global temperatures caused by the trapping of solar heat by gases in the atmosphere

74
Q

how might global warming affect the natural world?

A
  • temp, rainfall, light level affect survival
  • habitats may be destroyed by deforestation/flooding
  • species may need to change their habitat, or face extinction
75
Q

what is the nitrogen cycle

A

the cycle where nitrogen moves between living organisms and the environment, involving
- ammonification
- nitrification
- nitrogen fixation
- denitrification

76
Q

how do plant roots take up nitrogen

A

taken up via active transport and facilitated diffusion as ammonium and nitrate ions

77
Q

ammonium

A

NH4+

78
Q

nitrate ions

A

NO3-

79
Q

name the 4 types of bacteria involved in the nitrogen cycle

A
  • nitrogen-fixing bacteria
  • nitrifying bacteria
  • denitrifying bacteria
  • decomposers
80
Q

describe ammonification

A

the production of ammonium compounds when decomposers feed on organic nitrogen-containing molecules

81
Q

describe nitrification

A

the conversion of
atmospheric nitrogen gas –> ammonia

BY nitrogen-fixing bacteria in the soil/root nodules of legumes

82
Q

give some examples of nitrifying bacteria

A
  • azotobacter
  • rhizobium
83
Q

where does azotobacter live

A

freely in soil

84
Q

where does rhizobium live

A

inside the root nodules of leguminous plants

85
Q

describe nitrogen fixation

A

the conversion of
ammonium ions –> nitrate

BY nitrifying bacteria

86
Q

what are the 2 stages of nitrogen fixation

A
  1. Ammonium ions oxidised to nitrite ions
  2. nitrite ions oxidised to nitrate ions
87
Q

name the 2 types of nitrifying bacteria

A
  • nitrosomonas
  • nitrobacter
88
Q

what is the function of nitrosomonas

A

oxidises ammonium compounds into nitrites

89
Q

what is the function of nitrobacter

A

oxidises nitrites into nitrates

90
Q

describe denitrification

A

the conversion of nitrate ions to nitrogen gas by denitrifying bacteria

91
Q

what are denitrifying bacteria

A

anaerobic microorganisms, found in waterlogged soils, responsible for the reduction of nitrate ions to nitrogen gas

92
Q

explain the economic importance of the nitrogen cycle

A

maximises plant growth and crop yield, increasing food production

93
Q

name 3 methods farmers can use to increase the nitrate content of soil

A
  • ploughing and drainage to aerate the soil
  • application of fertilisers
  • growing legumes
94
Q

what are fertilisers

A

natural or artificial materials which are added to soils to provide essential nutrients and improve plant growth

95
Q

Give some examples of natural fertilisers

A
  • manure
  • compost
  • treated sewage
96
Q

give an example of an artificial fertiliser

A

ammonium nitrate

97
Q

what is eutrophication

A

pollution from nitrogen-containing fertilisers cause algal blooms and oxygen level reduction in water

98
Q

describe the 7 steps of fertilisers causing eutrophication

A
  1. fertilisers run-off into rivers
  2. nutrients build-up in water
  3. algal bloom blocks sunlight
  4. aquatic plants cannot photosynthesis ∴ less oxygen produced
  5. they die+decompose
  6. decomposers further decrease oxygen levels
  7. animals can’t respire ∴ die
99
Q

how does digging drainage ditches affect habitats

A
  • habitat loss
  • biodiversity reduction
  • may cause eutrophication
100
Q
A

WJEC Biology A-Level (14 decks)

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