How ecosystems work Flashcards

1
Q

Biomass

A
  • mass of organisms
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2
Q

Productivity

A
  • rate at which materials are produced

- energy transferred to a trophic level

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3
Q

Why does biomass of grass in ungrazed area decrease?

A
  • reduced photosynthesis due to long leaves blocking light
  • greater competition for water, nutrients, minerals
  • leaves dying
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4
Q

Why are there low levels of primary productivity in grazed area?

A
  • larger number of animals trample grass
  • overgrazing
  • grass unable to recover
  • little photosynthesis takes place
  • to much excretion
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5
Q

How fall in predators affects food chain / grassland productivity

A
  • decrease in predators results in an increase in predators’ prey, e.g. herbivores, fewer are killed
  • this leads to overgrazing by increased number of herbivores
  • reduction in producers, less primary productivity
  • less food for herbivores, herbivores die
  • increase in other carnivores
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6
Q

How changes in % of dead organic matter changes the number of species

A
  • less organic matter, fewer nutrients
  • unstable substrate
  • few species can tolerate conditions
  • pioneer species colonise
  • increased organic matter suits more species
  • increased competition
  • climax community established, fewer species where good soil is
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7
Q

Climax community

A
  • plant community that no longer changes in specie composition
  • due to succession
  • dominant species most abundant
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8
Q

Net primary production (NPP)

A
  • rate of production of new biomass
  • that is available to the next tropic level
  • NPP = GPP - respiration
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9
Q

Why only a small % of the light energy falling onto a leaf is converted into chemical energy

A
  • light reflected away from leaf
  • some light passes straight through leaf
  • plant cannot use all wavelengths of light
  • photosynthesis is not efficient
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10
Q

Why only 10% of energy locked up in secondary consumers is transferred to tertiary consumers

A
  • secondary consumers respire / loss as heat
  • they lose energy when they move around
  • not all of them are eaten
  • they have indigestible parts
  • decomposition of secondary consumers
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11
Q

Why decomposers have greatest energy transferring in

A
  • they obtain energy from all trophic levels
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12
Q

Why is slash and burn farming considered unsustainable

A
  • after a long time total biomass has not returned to original
  • fewer roots could lead to less water retention
  • fewer roots will lead to more soil erosion
  • leaf litter is loer so there will be less nutrients
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13
Q

How biodiversity could change by the practice of slash and burn

A
  • change in habitats
  • more light allowed in
  • exposure to wind (loss of shelter from wind)
  • exposure to light changes plant populations
  • may lead to soil erosion
  • plants cannot get established
  • animals might migrate
  • changes in plants causes changes in types of animals
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14
Q

Plagioclimax

A
  • a sub climax

- factor e.g. grazing that maintains the subclimax

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15
Q

How a grazed grassland could develop into a woodland community

A
  • remove grazer
  • allow different species to colonise
  • competitive effects, change in soil
  • will go through several stages
  • succession occurs
  • climax community established
  • change in specie composition
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16
Q

Factor that could affect population size of predator

A
  • climate
  • territory size
  • diseases
  • predation
  • water/food supply
17
Q

Gross primary productivity

A
  • Chemical energy fixed/ carbohydrates stored in producers by photosynthesis
  • the rate at which producers capture ad store a given amount of chemical energy as biomass in a given length of time
18
Q

Role of decomposers in food chain

A
  • decompose dead remains
  • using external digestion
  • to release nutrients (nitrates)
19
Q

Why is productivity lower in colder areas than tropical areas

A
  • temperature lower
  • slower enzyme activity
  • shorter growing season, less sunlight
  • less photosynthesis
  • less water
20
Q

Ways energy is lost

A
  • respiration
  • faeces/indigestible material
  • nitrogenous waste
21
Q

Why are food chains of limited length

A
  • small proportion reaches next level

- insufficient energy to support another level

22
Q

Why is it important that compost is not allowed to become water logged or compacted

A
  • compact gives rise to anaerobic conditions
  • aerobic respiration not possible
  • denitrifying organisms break nitrogen containing into nitrogen
23
Q

Reasons for causes of desertification

A
  • overgrazing
  • lack of rainfall
  • climate change, e.g global warming
24
Q

Explain the process of desertification

A
  • loss of vegetation due to overgrazing
  • trampling compacts soil and removes plants
  • soil is exposed to wind and sun
  • soil blown away, evaporation of water from soil
  • loss of roots loosens soil
25
Way to prevent desertification
- put in a barrier, e.g. hedges, to reduce wind speed and provide shelter - use plants that are drought resistant, these plants can survive - plant fuel crop, sustainable - rain water harvesting, irrigate land - control grazing, e.g. density of animals to prevent loss of vegetation cover - supply water to live stock
26
Biotic factor
- involve other living organisms
27
Abiotic factor
- involve physical/chemical non-living things
28
Explain why GPP increases greater than NPP
- more energy is used in metabolism in bigger plants - for protein synthesis and flower initiation - herbivores cannot digest all parts - more photosynthesis tissue
29
Relationship between GPP, NPP and respiration
- GPP - NPP = R | - biomass production reduced by respiration
30
Why only a proportion of the organic material, formed using CO2, will become plant tissues
- respiration of some of the organic material | - energy is required for synthesis of molecules, movement and active transport
31
Abiotic factors that can affect gross primary production
- light intensity, duration, wavelength - temperature - CO2 concentration - pH
32
Why does oxygen uptake increase for dead plant material
- dead plant material is decomposed - by the action of microorganism - which respire aerobically - more dead material provides more nutrients which leads to an increase in microorganism
33
Why might there be a high number of predators
- GPP increases - indicating high plant population - plants releases O2 by photosynthesis - more plants mean more herbivores - more food for predators
34
How plant species vary as a result of succession
- difference communities at different distances - few species near beach, more further away as organic matter increases with distance, increasing number of niches - pioneer species colonise empty inorganic surfaces, penetrating rock breaking it up, allowing organic material to accumulate - increased organic matter results in increased water retention, mineral content - less hostile conditions, larger plants can be supported - better adapted plants out compete others, dominant specie is usually largest and most abundant - eventually climax community is reached. specie range is constant and dominated by a few species
35
Explain the difference between abiotic and biotic factors
- biotic factors involve organisms and abiotic factors are physical/chemical non-living factors