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Biology A2 Rafa > 6.5 Ecosystems > Flashcards

6.5 Ecosystems Flashcards

1
Q

What are abiotic factors?

A

non-living components of an ecosystem that affect other living organisms

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2
Q

What are biotic factors?

A

environmental factors associated with living organisms in an ecosystem that affect each other. e.g. predation, disease

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3
Q

Define ecosystem

A

A community of animals, plants and bacteria interrelated with the physical and chemical environment

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4
Q

Examples of biotic factors

A
  • producers
  • consumers
  • decomposers
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5
Q

Examples of abiotic factors

A
  • pH
  • relative humidity
  • temperature
  • concentration of pollutants
  • weather, eg storms
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6
Q

Why do we refer to ecosystems as dynamic?

A

Because they change

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7
Q

Three types of changes in ecosystems that affect population size?

A
  • cyclic changes (moving tides and changes in day)
  • directional changes (erosion of coastline)
  • unpredictable/ erratic changes (lighting and hurricanes)
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8
Q

What is biomass transfer?

A

transfer of biomass from one trophic level to another

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9
Q

What is a trophic level?

A

the level at which an organism feeds in a food chain

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10
Q

How is biomass lost from a food chain?

A
  • lost as heat, CO2 and water

- dead organisms and waste material, only available to decomposers

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11
Q

What does the area if a pyramid of biomass represent?

A

Its proportional to the dry mass of the organisms at that trophic level

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12
Q

How do you calculate the dry mass of an organism?

A

-collect organisms
-oven at 80 degrees until all water has evaporated
(destructive so use wet mass and calculate dry mass on the basis of previously published data)

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13
Q

Equation to calculate the efficiency of biomass transfer between trophic levels?

A

Ecological efficiency = (Biomass at higher trophic level/biomass at lower trophic level) x 100
efficiency=(biomass/ biomass transferred) x 100

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14
Q

What is productivity?

A

The rate of production of new biomass by producers

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15
Q

What is gross primary productivity?

A

the rate at which plants convert light energy to chemical energy by photosynthesis

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16
Q

How can you increase gross primary productivity using light?

A
  • light banks

- crops planted early to provide a longer growing season to harvest more light

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17
Q

Ways to increase gross primary productivity?

A
  • light levels
  • irrigating/ drought resistant crops
  • increasing temp
  • nutrients
  • removing pests
  • removing competition from weeds for light, water and nutrients (herbicides)
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18
Q

How can you increase gross primary productivity using temperature?

A

Greenhouses, increases photosynthesis and rate of production of biomass
-planting crops early to provide a longer growing season helps avoid effect of temperature on final yield

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19
Q

How can we increase gorss primary production using nutrients?

A
  • crop rotation (growing a different crop in each field of rotational cycle)
  • including nitrogen fixing crop, such as peas or beans replenishes nitrogen levels
  • some crops bred to respond to high levels of fertiliser
20
Q

How does crop rotation help conservation of biomass?

A

Stops reduction in soil levels of inorganic materials such as nitrate or potassium

21
Q

How can we increase gross primary production that is reduced by pests and fungi?

A
  • pesticides
  • some plants have been bred to be pest resistant
  • fungicides
22
Q

How can you increase secondary productivity?

A
  • harvesting animals before adulthood (no loss of energy for growth)
  • selective breeding (fast growth rates)
  • treating with antibiotics (no loss of energy to pathogens and parasites)
  • constant temperatures
  • supplying food
23
Q

Steps of saprotrophic decomposition…

A
  • saprotrophs secrete enzymes onto dead material
  • enzymes digest material into small molecules which are absorbed
  • molecules are stored or respired
24
Q

Examples of fixed nitrogen

A

NH4+ or NO3-

25
Q

Examples of nitrogen fixation

A

Lighting strikes
Haber process
Nitrogen fixing bacteria

26
Q

What are nitrogen fixing bacteria that live in the soil called?

A

Azotobacter

27
Q

Which nitrogen fixing bacteria live in root nodules?

A

Rhizobium

They have a mutualistic relationship with plant, provide nitrogen and receive glucose in return

28
Q

Examples of plants that have rhizobium?

A

peas, beans and clover

members of bean family

29
Q

Difference between habitat and niche

A
  • Habitat is where organism

- Niche is the role an organism fulfils in an ecosystem

30
Q

Define climax community

A

the final stable community that exists after the process of succession has occurs

31
Q

Three types of productivity that I need to be comfortable with

A
  • gross primary productivity (rate at which plants covert light energy into chemical energy)
  • net primary productivity
  • secondary productivity
32
Q

Two main types of nitrogen fixing bacteria

A

Rhizobium and axotobacter

33
Q

Bacteria from ammonium to nitrites

A

nitrosomonas

34
Q

Bacteria from nitrites to nitrates

A

nitrobacter

35
Q

Conditions for denitrification

A

anaerobic

36
Q

Examples of chemoautotrophic bacteria

A

Nitrosomonas and nitrobacter

37
Q

What is deflected succession?

A

Happens when succession is stopped or interfered with, such as by grazing or when a lawn is mowed

38
Q

Define pioneer species

A

the species that begin the process of succession, often colonising an area as the first living things there

39
Q

Define succession

A

A progressive change in a community of organisms over time

40
Q

What is secondary succession?

A

Succession that occurs on previously colonised but disturbed or damaged habitat

41
Q

Example of primary succession

A

On Surtsey in Iceland - formed in 1960s

  • algae and lichens live and die
  • death and erosion of rock makes soil
  • larger plants can grow etc to climax community
42
Q

What is a community called thats sub-climactic?

A

Plagioclimax

43
Q

What does random sampling use?

A

point quadrat/frame (higher up)

quadrate/frame

44
Q

How do you use a point quadrat?

A

Higher up quadrat

You drop pin down and count all plants touching it

45
Q

How can you calculate the total population size using quadrats?

A

total population size = mean number of individuals of the species in each quadrat/fraction of total habitat area covered by a single quadrat

46
Q

Two approaches to using a transect

A
  • Line transect (at regular intervals, make note of which species touching the tape)
  • Belt transect (at regular intervals, place quadrat next to line and move along)

Biology A2 Rafa (14 decks)

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