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z - A Level Biology > 6.3.1: Ecosystems > Flashcards

6.3.1: Ecosystems Flashcards

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1
Q

Ecosystem

A

Any group of living organisms and non-living things occurring together, and the interrelationships between them.

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2
Q

Ecosystems are affected by what?

A

Biotic and abiotic factors

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3
Q

Abiotic factors

A

non-living components e.g. pH, temperature, soil type

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4
Q

Biotic factors

A

living components e.g. food supply, predation and disease

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5
Q

Habitat

A

the place where an organism lives

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6
Q

Population

A

all organisms of 1 species living in the same place at the same time, can breed together.

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7
Q

Community

A

All populations of species living in the same place at the same time and can interact together

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8
Q

Niche

A

role each species plays in an ecosystem e.g. through feeding, excretion and reproduction etc. No two species can occupy exactly the same niche.

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9
Q

Why do diagrams of biomass give a pyramid shape?

A

1) Not all of the previous trophic level is eaten
2) Some parts not digested so not all absorbed
3) Small fraction of materials end up as new cells in the next organisms (this happens at each trophic level)

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10
Q

Limits of a pyramid of energy

A

It is a snapshot of an ecosystem at 1 moment in time (ecosystems are dynamic)
Population sizes can fluctuate over time

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11
Q

How is the energy in an organism calculated?

A

Dry weight organism
Burn organism in calorimeter
Change in temp. of water –> work out from this energy released per gram

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12
Q

Ecological efficiency (definition)

A

the efficiency with which biomass or energy is transferred from one trophic level to the next

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13
Q

Ecological efficiency (formula)

A

(energy or biomass available after transfer / energy or biomass available before transfer ) x 100

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14
Q

Edaphic factors

A

soil factors, e.g. type of soil, particle size, drainage

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15
Q

Gross (primary) production

A

the rate at which a plant converts light energy into chemical energy

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16
Q

Denitrification

A

the conversion of nitrate ions into nitrogen gas

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17
Q

the conversion of nitrate ions into nitrogen gas

A

Denitrification

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18
Q

A bacterium that fixes nitrogen

A

Rhizobium

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19
Q

The conversion of ammonium ions into nitrite ions

A

Nitrification

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20
Q

Nitrification

A

The conversion of ammonium ions into nitrite/nitrate ions

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21
Q

Bacterium that carries out denitrification

A

Clostridium

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22
Q

Bacterium that carries out nitrification

A

Nitrosomonas, Nitrobacter

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23
Q

Clostridium

A

Bacterium that carries out denitrification

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24
Q

Nitrosomonas, Nitrobacter

A

Bacterium that carries out nitrification

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25
Q

Denitrifcation requires

A

anaerobic conditions

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26
Q

Nitrogen fixing (often) requires

A

anaerobic conditons so the enzyme nitrogen reductase can work

27
Q

Ammonification

A

conversion of nitrogen compounds in dead organic matter or waste into ammonium compounds by decomposers.

28
Q

What do plants need nitrogen for?

A

DNA, RNA, amino acids, ATP, protein synthesis

29
Q

% of nitrogen in the air?

A

71%

30
Q

Why can’t plants use nitrogen gas?

A

It is insoluble; cannot be absorbed

31
Q

What is the main point of/why do we care about the nitrogen cycle?

A

To create nitrate ions –> the form of nitrogen that plants can absorb

32
Q

Nitrate ions =

A

NO3-

33
Q

Example of free-living (nitrogen-fixing) bacteria

A

Azobacter

34
Q

Nitrogen fixing bacteria that lives in root nodules

A

Rhizobium

35
Q

What gases do denitrifying bacteria release?

A

nitrogen and nitrous oxide

36
Q

What does nitrogen reductase do?

A

Catalyses the breakdown of N-N triple bond, adding 3 H atoms to each N

37
Q

Succession

A

Directional changes in the species of organisms living in a community that occur over time due to changes in the environment.

38
Q

Types of succession

A

Primary

Secondary

39
Q

What is primary succession?

A

Development of a community from bare ground
Pioneer community colonise first e.g. algae and lichen on bare rock
Build up of dead organisms and rock erosion forms soil for large plants e.g. mosses

40
Q

What is secondary succession?

A

Development of a community on previously colonised but disturbed/damaged habitat (e.g. after forest fire)
Soil is present but there are no plant/animal species

41
Q

Different communities (stages)

A

Pioneer community –> Intermediate community –> climax community

42
Q

Plagioclimax

A

the final stage that is formed when succession is halted artificially (i.e. when humans prevent the ecosystem from reaching a climax community) e.g. clearing scrubland to grow crops, burning for deforestation

43
Q

Features of a pioneer community

A

Low species biodiversity
Instability
Small

44
Q

Carrying capacity

A

the maximum population size that can be maintained over a period of time in a particular habitat

45
Q

Different phases of population growth

A

1: lag phase
2: log phase
3: stationary phase

46
Q

When do limiting factors have the most effect?

A

As population size gets closer to carrying capacity

47
Q

Density independent factors

A

Affect populations equally regardless of size

e.g. earthquakes, volcanoes, fires, storms

48
Q

Density dependent factors

A

Affect populations differently according to size

e.g. disease spreads quicker in more dense populations

49
Q

Conservation

A

maintenance of biodiversity through human action or management e.g. controlled grazing, sustainable timber
Can use resources but not beyond the point of recovery

50
Q

Preservation

A

completely halting human activity (in an effort to preserve an area) e.g. building a fence around it

51
Q

Reclamation

A

restoring ecosystems that have been damaged or destroyed.

Can include use of controlled burning of forest which can stop succession and increase biodiversity

52
Q

Economic reasons for conservation

A 
Ecosystems conduct valuable processes:
• Nutrient cycling
• Cleaning water
• Providing an atmosphere/cleaning the air
• Provision of food
• Provision of building materials
53
Q

Social reasons for conservation

A

Ecosystems provide pleasant environments that can have mental and physical health benefits

54
Q

Ethical reasons for conservation

A
  • All organisms have a right to exist
  • Humans have been responsible for destructive of habitats/hunting of species to extinction –> now have a duty of care to preserve ecosystems
  • Moral responsibility to future generations
55
Q

Conservation - how?

A

• Legal protection to endangered species
• Zoos/botanic gardens (ex situ conservation)
• Manage ecosystems
⟶ Raise carrying capacity by providing food for some species
⟶ Control poachers and predators
⟶ Prevent pollution
⟶ Restrict succession by coppicing/grazing
⟶ Eradicate unwanted species that have been introduced
⟶ National Parks, green belts, SSSIs

56
Q

Sustainability

A

Resources are exploited in a way that means they won’t run out and will be available for future generations

57
Q

Aims of sustainability

A
  • Conserve environment
  • Ensure resources are available fo future generations
  • Allow people to live comfortably
  • Allow LEDCs to develop through exploitation of their natural resources
58
Q

Population size of species (Lincoln index)

A

No. of individuals in 1st sample x no. individuals in second sample / number recaptured marked individuals

59
Q

Main principles of ecotourism

A

Balancing human needs with the needs of the ecosystem
Type of sustainable development
No exploitations
Consultation with local people
Infrastructure must be available for use by local people as well as tourists

60
Q

Why to conserve/preserve peat bogs?

A

Biodiversity
Erosion control
Carbon storage
Flood management

61
Q

Human activites that lead to destruction of peat bogs

A

Afforestation
Peat extraction
Agricultural intensification
Pollution–> acid rain (kills moss, peat underneath washed away)

62
Q

How to conserve peat bogs?

A

Removal of seedlings from an area
Use of controlled grazing
Ensure peat and vegetation of bog as undisturbed as possible

63
Q

Nitrogen fixing

A

conversion of atmospheric nitrogen gas into ammonium ions

z - A Level Biology (25 decks)

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