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A LEVEL BIOLOGY > 5 - Population Size and Ecosystems (C1) > Flashcards

5 - Population Size and Ecosystems (C1) Flashcards

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1
Q

What is gross primary productivity? (GPP)

A

The rate at which plants fix energy into organic molecules, by photosynthesis, in a given area and time

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2
Q

What is net primary production? (NPP)

A

The rate at which energy in organic molecules present in plants is made available for herbivores in a given area and time

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3
Q

What is the equation linking GPP and NPP?

A

NPP = GPP - respiration

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4
Q

What is succession?

A

The change in structure and species composition of a community over time as the environment improves or better adapted species survive

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5
Q

What are seral stages?

A

The different stages in a succession when particular communities dominate

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6
Q

What are the 4 phases of growth?

A
  • Lag phase - Exponential phase - Stationary phase - Death phase
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7
Q

What happens during the lag phase?

A
  • Bacteria are adapting and preparing for growth - Organisms like rabbits are waiting to reach sexual maturity and find mates
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8
Q

What happens during the exponential phase?

A
  • Bacterial cells divide at a constant rate and the population doubles per unit time - More organisms become ready for reproduction
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9
Q

What happens during the stationary phase?

A
  • Rate of increase slows as there is less space, food, etc. - Birth rate = death rate - Population has reached the carrying capacity for that particular environment
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10
Q

What happens during the death phase?

A
  • The factors that slow down population growth at the end of the lag phase become more significant - Population size decreases until death rate > birth rate - Graph will have negative gradient
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11
Q

What are density dependent factors?

A

When the population density increases, the effect is increased (biotic factors)

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12
Q

What are density independent factors?

A

When the population density increases, the effect is the same (abiotic factors)

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13
Q

What is the carrying capacity?

A

The maximum number of individuals that an area can support

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14
Q

What is the source of energy for most food chains?

A

The sun

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15
Q

What are some reasons why energy in plants may not be passed on to animals that eat them?

A
  • Animals only eat a small amount of the plants - Cellulose is difficult for animals to digest - Energy is lost in respiration
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16
Q

What are some reasons why energy in animals may not be passed on to animals that eat them?

A
  • Energy released by respiration is used for movement - ENergy is lost as waste, such as in faeces - Predators only consume small amounts of animal as some parts are not digestible
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17
Q

What happens to the energy present in faeces and dead plants and animals?

A

It’s consumed or processed into useful nutrients by microorganisms that use digestive enzymes to break down complex molecules into simpler nutrients

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18
Q

Why are pioneer plants often xerophytes that can fix nitrogen?

A

Xerophytes are adapted to decrease water loss and have long roots to absorb as much water as possible. They fix nitrogen as there are few nutrients available

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19
Q

What are pioneer species?

A

The first species to colonise a new area in an ecological succession

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20
Q

Why is energy in GPP less than the energy available from the sun?

A
  • Light energy misses the plant - Light reflects off leaves - Light passes through leaves - Light is absorbed by non-photosynthetic parts - Only red and blue light can be used in photosynthesis
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21
Q

What is the order of groups in the food change?

A
  • Primary producers - Primary consumers - Secondary consumers - Tertiary consumers
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22
Q

What is meant by the trophic level?

A

The number of stages that an organism is from the start of the food chain

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23
Q

What is meant by the term carbon footprint?

A

The amount of CO2 released into the atmosphere per year as a result of the activities of a particular individual, organisation or community

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24
Q

What is the name of the group of plants that have a large number of root nodules on their roots?

A

Legumes

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25
Q

What is the advantage for legumes by having root nodules?

A
  • Contain nitrogen fixing bacteria - Some nitrogenous compounds pass to the plant - Allows the plant to grow in poor soil
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26
Q

Why are nitrogen and phosphorus needed for plant growth?

A
  • Nitrogen is needed for protein production - Phosphorus maintains the phospholipid bilayer
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27
Q

What is an example of a biological molecule that contains sulphur?

A

Amino acid

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28
Q

What is the definition of a population?

A

An interbreeding group of organisms of the same species in one area at one time

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29
Q

What is the definition of a community?

A

Interacting populations of 2 or more species in the same habitat at the same time

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30
Q

What is the definition of an ecosystem?

A

A characteristic community of interdependent species interacting with the abiotic components of their environment

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31
Q

What is the definition of niche?

A

The role of an organism within the place where it lives (what it eats, etc)

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32
Q

What is the definition of an abiotic factor?

A

A part of the environment of an organism that is non-living e.g. O2 availability

33
Q

What is the definition of a biotic factor?

A

A part of the environment of an organism that is living e.g. pathogens, predators

34
Q

What is the definition of immigration?

A

The movement of individuals into a population of the same species

35
Q

What is the definition of emigration?

A

The movement of individuals out of a population of the same species

36
Q

What is the definition of an equilibrium species?

A

Species that control their population by competition rather than by reproduction and dispersal

37
Q

What does a pyramid of numbers show?

A

The number of organisms at each trophic level

38
Q

What does a pyramid of biomass show?

A

The mass of organisms present at each trophic level

39
Q

What does a pyramid of energy show?

A

The energy present in the biomass produced in a year at each trophic level

40
Q

What is intraspecific competition?

A

Competition between individuals of the same species

41
Q

What is interspecific competition?

A

Competition between individuals of different species

42
Q

Why is intraspecific competition more intense than interspecific competition?

A

Because individuals have more needs in common

43
Q

What is facilitation?

A

When a species which occurs in a succession grows more readily when another species is present

44
Q

What is commensalism?

A

When one species benefits from the presence of another without affecting the other

45
Q

What happens in nitrification?

A

Nitrosomonas oxidises ammonia to nitrite, and Nitrobacter oxidises nitrite to nitrate - Requires aerobic well-drained soil (as the nitrogen atom in the ammonium ion progessively loses hydrogen atoms and gains oxygen atoms)

46
Q

What happens in denitrification?

A
  • Removal of O2 from nitrate producing nitrogen, by denitrifying bacteria (e.g. pseudomonas) so they may respire - Occurs in anaerobic, water-logged soil
47
Q

What happens in ploughing?

A
  • Soil is aerated - Increases nitrification, decreases denitrification
48
Q

What is ammonification / putrefaction?

A
  • Decomposition of dead material, urine and faeces to ammonium ions by bacteria and fungi
  • Bacteria and fungi secrete enzymes: proteases digest proteins into amino acids, deaminases reduce amino acids to ammonium ions
49
Q

What are disadvantages of the nitrogen cycle?

A
  • Nitrates are very soluble and are washed out of the soil in a process called leaching - Nitrates are washed into rivers, lakes and the sea leading to eutrophication
50
Q

What is eutrophication?

A
  • Nitrate (NO3) causes algae to grow on surface of water = algal bloom - No light reaches plants on stream bed so they die - Aerobic decomposing bacteria use up available O2 as they multiply - Lack of O2 kills fish etc.
51
Q

What is secondary productivity?

A

The rate at which consumers accumulate energy in the form of cells or tissue

52
Q

What is primary succession?

A

The change in structure and species composition of a community over time in an area that has not previously been colonised

53
Q

What is secondary succession?

A

The recolonisation of a habitat previously occupied by a community, following disturbance or damage

54
Q

What is the name of the fungi involved in the breakdown of leaf litter?

A

Saprotrophic fungi

55
Q

What is the definition of ecology?

A

The study of the interaction of organisms with their natural environment

56
Q

What is the definition of abundance?

A

The number of individuals in a species in a given area or volume

57
Q

Why can’t quadrats be used to measure animal populations, and what method is used?

A
  • They’re motile - Mark and recapture: * Catch, count and mark animals * Repeat * Find total pop = (no. marked x total in 2nd catch) div. by no. marked in 2nd catch
58
Q

What is the nitrogen cycle?

A

The flow of organic and inorganic nitrogen within the abiotic and biotic components of an ecosystem where there is an interchange between certain nitrogenous bases and atmospheric nitrogen

59
Q

What is the definition of distribution?

A

The area or volume in which the organisms of a species are found

60
Q

Which organisms start decomposition and which ones finish it?

A
  • Detrivores, e.g. earthworms and woodlice, start the process - Decomposers, e.g. bacteria and fungi, complete the process
61
Q

What is the definition of primary productivity?

A

The rate at which energy is converted by producers into biomass

62
Q

What is the definition of secondary productivity?

A

The rate at which consumers convert the chemical energy of their food into biomass

63
Q

What are problems with using pyramids of numbers?

A
  • They don’t consider the size of organisms - Don’t differentiate between young and adult forms
64
Q

What are problems with using pyramids of biomass?

A
  • Biomass is difficult to measure, e.g. plant roots must be included - Organisms contain structures with mass that aren’t transferred to the next trophic level e.g. bones, beaks - Don’t show the energy flow
65
Q

What is the definition of a climax community?

A

A stable, self-perpetuating community that has reached equilibrium with its environment, and no further changes occur

66
Q

What is a xerosere sequence?

A

Pioneers -> herbs and grasses -> shrubs and small trees -> large trees

67
Q

What is mutualism?

A

An interaction between organisms of 2 species from which both derive benefit

68
Q

Why does decomposition produce CO2?

A

Dead animals and plants have taken in carbohydrates, fats and proteins which are released as CO2 when they’re decomposed by detritivores and saprobionts

69
Q

What are the 2 main causes of climate change?

A
  • Burning fossil fuels
  • Deforestation (as it releases O2 stored in trees, and reduces photosynthesis)
70
Q

What is global warming?

A

The increase of average global temperature, in excess of the greenhouse effect, caused by the atmosphere’s historical conc of CO2

71
Q

What is the greenhouse effect?

A
  • Gases such as Co2, methane and CFCs surround the earth
  • They allow solar radiation to pass to the Earth’s surface, much of which is absorbed by Earth, which warms and re-radiates infra-red radiation
  • This is absorbed and trapped by the greenhouse gases which re-radiate it back to Earth, heating it more
72
Q

What are some consquences of global warming?

A
  • Melting of polar ice resulting in flooding in coastal areas
  • More extreme weather conditions e.g. droughts, hurricanes
  • Increase in CO2 in oceans decreases the PH, distrubting marine life
  • Increased freq of forest fires
73
Q

What are the 3Rs, publicised to reduce the production of greenhouse gases?

A

Reduce, reuse, recycle

74
Q

What is nitrogen fixation?

A
  • Reduction of nitrogen molecules to ammonium ions by Azotobacter and Rhizobium
  • Nitrogenase catalyses the reduction using energy from ATP
  • Lots of energy is required so nitrogen-fixing organisms are often aerobic
  • NF requires reduction reactions and is poisoned by oxidising conditions so root nodules contain leg-haemoglobin which binds molecular O2 in the nodules and protects the reactions from oxidation
75
Q

What are 3 processes that impact the nitrogen cycle?

A
  • Application of agricultural fertilisers adds nitrogen to soil
  • Lightning adds a small amount of nitrogen to soil
  • Leaching of minerals removes nitrogen from soil
76
Q

How does ploughing improve the circulation of nitrogen?

A

It favours:

  • Aerobic organisms, such as nitrogen fixers, enhancing the formation of ammonium ions in soil
  • Nitrifying bacteria and so enhances the conversion of ammonium into nitrites and nitrates
  • Plant roots respire aerobically and generate ATP, which fuels their active uptake of minerals
77
Q

What human activities improve the circulation of nitrogen in agricultural soils?

A
  • Ploughing
  • Draining land
  • Artificial nitrogen fixation e.g. Haber process
  • Putting animal waste onto soil
78
Q

What problems can the use of nitrogen-containing fertilisers cause?

A
  • Reduces species diversity on grassland
  • Fertilisers increase the growth of grasses and plants which shade smaller plants
  • Eutrophication in lakes and rivers
79
Q

How does draining land and ploughing fields prevent denitrification?

A

Increase aeration so anaerobic bacteria can’t compete with aerobic bacteria

A LEVEL BIOLOGY (13 decks)

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