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Gcse Biology > Topic 9 - Ecosystem And Material Cycle > Flashcards

Topic 9 - Ecosystem And Material Cycle Flashcards

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1
Q

Describe mutualism

A

The interaction between two organisms where both benefit as a result of their relationship

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2
Q

Describe parasitism

A

The interaction between two organisms where only one organism, the parasite, benefits whilst the host does not

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3
Q

What are abiotic factors? Give some examples.

A

The non-living aspects of an ecosystem

e.g. temperature, water availability, light intensity, pollutants

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4
Q

What are biotic factors? Give some examples.

A

The living components of an ecosystem e.g. competition, predation

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5
Q

What piece of apparatus is used to measure the abundance and distribution of organisms in an area?

A

Quadrat

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6
Q

What piece of apparatus is used to study the distribution of organisms across a gradient?

A

Belt transect

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7
Q

What does a food chain show?

A

It describes the feeding relationships between organisms and the resultant stages of biomass transfer.

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8
Q

Define biomass

A

The total mass of living material

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9
Q

What are trophic levels?

A

The stages in a food chain

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10
Q

What do arrows in a food chain represent?

A

The direction of biomass transfer

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11
Q

Describe a simple food chain

A

producer → primary consumer →

secondary consumer → tertiary consumer

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12
Q

Why are producers the first trophic level?

A

Producers provide all biomass for the food chain (via photosynthesis)
● The rest of the food chain involves the transfer of this biomass

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13
Q

What does a pyramid of biomass represent?

A

It represents the dry mass of living material at each trophic level of a food chain.

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14
Q

Why is a pyramid of biomass almost always pyramid-shaped?

A

Producers (at the bottom of the pyramid) have the greatest biomass so have the longest bar
● As you move along the food chain (and up the pyramid) biomass is lost so the bars decrease in length

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15
Q

Why is biomass lost between each trophic level in a food chain?

A

● Glucose is immediately used for respiration in plants
● Respiration to generate heat energy, energy for movement etc.
● Some parts of organisms are indigestible
● Egestion, excretion

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16
Q

Why are there rarely more than four or five trophic levels in a food chain?

A

Above this, there is insufficient energy to support another breeding population.

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17
Q

What is the equation for calculating the efficiency of biomass transfer between trophic levels?

A
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18
Q

What is biodiversity?

A

The variety of living organisms in an ecosystem.

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19
Q

How does fish farming affect biodiversity?

A

Food used to feed the fish and waste can leak into water sources, causing eutrophication
● Parasites from fish farms may spread and contaminate surrounding ecosystems
● Other organisms may become tangled in netting

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20
Q

How does the use of fertilisers affect biodiversity?

A

Excess fertiliser can wash into water sources causing eutrophication and death of many species. This reduces biodiversity.

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21
Q

Describe how fertilisers can cause eutrophication

A
  1. Fertiliser run-off into rivers and lakes
  2. Nutrients build-up in water
  3. Algal bloom blocks sunlight
  4. Aquatic plants cannot photosynthesise ∴ less oxygen produced
  5. They die and decompose
  6. Decomposers further deplete oxygen levels
  7. Animals can no longer respire aerobically so die
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22
Q

How does the introduction of non-indigenous species affect biodiversity?

A

● They may out-compete native species, causing a reduction in population numbers
● Native species may become the prey of non-indigenous species
● They may bring new diseases which could kill large numbers of native species, reducing biodiversity

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23
Q

How can humans more positively impact biodiversity?

A

Protection of endangered species e.g. making hunting illegal, breeding programmes increase population sizes
● Conservation schemes e.g. national parks, seed banks, zoos
● Reforestation
● Sustainable farming e.g. fewer pesticides
● Minimising global greenhouse gas production

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24
Q

How do conservation schemes protect biodiversity?

A

They prevent species from becoming extinct and increase population numbers, maintaining biodiversity.

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25
Q

Outline the benefits of maintaining biodiversity

A

Ensures future food requirements can be met, reduces damage to food chains
● Increases the likelihood of species adapting to future environmental change
● Many plant species are yet to be discovered and may contain chemicals that could be used in future medicines
● Safeguarding valuable future resources e.g. fuels, paper
● Aesthetics - culture, ecotourism etc.
● Jobs provided by ecotourism, reforestation and conservation schemes

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26
Q

What is food security?

A

Ensuring that populations have access to adequate amounts of safe and nutritious foods

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27
Q

List the biological factors affecting food security (5)

A 
● Rising human population
● Changing diets
● New pests and pathogens
● Environmental change
● Sustainability
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28
Q

Describe how the rising human population affects food security

A

As human population increases, global food production must also increase in order to meet the growing demand for food.

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29
Q

Describe how changing diets affect food security

A

● Greater consumption of meat and fish in wealthier populations
● Less energy and biomass available from livestock than crops
● Livestock use land for grazing and are fed crops that could otherwise be used for human consumption
● Less food is available for humans ∴ reduction in food security

30
Q

Describe how new pests and pathogens affect food security

A

Pests and pathogens can reduce or destroy crop yields, negatively impacting food security.

31
Q

Describe how sustainability affects food security

A

Unsustainable farming methods disrupt food chains, compromising the ability to meet future food requirements
● Due to the high input costs, many LEDCs cannot maintain modern farming methods
● Using land for biofuel production reduces land available for crops

32
Q

Describe how environmental change due to human activity affects food security

A

● Emissions of greenhouse gases have been linked to global warming which may affect crop growth
● Salinisation reduces agricultural potential of soils

33
Q

What are the three types of nutrient cycle?

A

● Carbon cycle ● Water cycle

● Nitrogen cycle

34
Q

Why are the nutrient cycles important?

A

Carbon, water and nitrogen are essential to life

● There is a fixed amount of nutrients on Earth which must be constantly recycled

35
Q

Describe how materials cycle through the living and non-living components of an ecosystem

A

Organisms take in elements from their surroundings e.g. soil, air
● Elements converted to complex molecules which become biomass
● Elements transferred along food chains
● Elements returned to environment during excretion and decomposition of dead organisms

36
Q

Describe the stages of the carbon cycle

A

Photosynthesising plants remove CO2 from the atmosphere

  1. Eating passes carbon compounds along a food chain
  2. Respiration in plants and animals returns CO2 to the atmosphere
  3. Organisms die and decompose. Decomposers (bacteria and fungi) break down dead material and release CO2 via respiration
  4. Combustion of materials (e.g. wood, fossil fuels) releases CO2
37
Q

Describe the stages of the water cycle

A
  1. Energy from the sun evaporates water from sources such as lakes and oceans. Transpiration also releases water vapour.
  2. Water vapour rises, cools and condenses forming clouds
  3. Precipitation occurs
  4. Water is absorbed by the soil and taken up by roots. Some is used in photosynthesis or becomes part of the plant, entering the food chain.
  5. Excretion returns water to the soil
  6. Surface runoff returns to streams, rivers and eventually the sea
38
Q

What is potable water?

A

Drinking water

39
Q

How can potable water be prepared?

A

Desalination

40
Q

What is desalination?

A

A process that removes salts from saline water

41
Q

Name two methods of desalination

A

● Thermal desalination ● Reverse osmosis

42
Q

Describe thermal desalination

A

Salt water is boiled. Water evaporates, rises and condenses down a pipe. This separates pure water from salts.

43
Q

Describe reverse osmosis

A

● Saline water pumped into a vessel containing a partially permeable membrane at high pressure
● High pressure forces water molecules to move from an area of low water concentration (high salt concentration) to an area of high water concentration (low salt concentration)
● Pure water separated from salts

44
Q

What do plants use to make proteins?

A

Nitrates

45
Q

Why can’t nitrogen be used directly by plants to form proteins?

A

Nitrogen is unreactive

46
Q

Name the four types of bacteria involved in the nitrogen cycle

A

● Decomposers
● Nitrogen-fixing bacteria ● Nitrifying bacteria
● Denitrifying bacteria

47
Q

What is the role of decomposers in the nitrogen cycle?

A

● Break down proteins and urea into ammonia

● Ammonia dissolves in solution forming ammonium ions

48
Q

What is the role of nitrogen-fixing bacteria in the nitrogen cycle?

A

● Convert nitrogen gas into ammonia

● Ammonia dissolves in solution forming ammonium ions

49
Q

Where are nitrogen-fixing bacteria found?

A

Soil

● Root nodules of legumes

50
Q

What type of relationship is exhibited between nitrogen-fixing bacteria and legumes?

A

● Mutualistic relationship

● Plants receive ammonium ions from bacteria ● Bacteria gain sugars from the plant

51
Q

What is the role of nitrifying bacteria in the nitrogen cycle?

A

● Convert ammonium ions into nitrites ● Convert nitrites into nitrates

52
Q

What is the role of denitrifying bacteria in the nitrogen cycle?

A

Convert nitrates into nitrogen gas

53
Q

Where are denitrifying bacteria commonly found?

A

Waterlogged soils

54
Q

Describe the stages of the nitrogen cycle

A
  1. Lighting and nitrogen-fixing bacteria convert nitrogen gas to ammonia which dissolves to form ammonium ions
  2. Nitrifying bacteria convert ammonium ions to nitrate ions which are taken up by plants and used to build proteins
  3. Feeding passes nitrogen through the food chain
  4. Organisms die and decompose. Decomposers break down proteins and urea
    to form ammonia which dissolves to form ammonium ions
  5. Denitrifying bacteria convert nitrates in the soil back to nitrogen gas
55
Q

How can the amount of nitrates in the soil be increased?

A

● Using fertilisers e.g. animal manure, compost, artificial fertilisers
● Crop rotation replenishes nitrates that may have been depleted by the previous crop e.g. planting a nitrogen-fixing crop

56
Q

What is meant by decomposition?

A

The breakdown of dead materials into simpler organic matter

57
Q

How do decomposers break down dead matter?

A

Decomposers release enzymes which catalyse the breakdown of dead material into smaller molecules.

58
Q

What factors affect the rate of decomposition?

A

● Oxygen availability ● Temperature

● Water content

59
Q

Why is oxygen required for decomposition?

A

Most decomposers require oxygen for aerobic respiration

60
Q

How does the availability of oxygen affect the rate of decomposition?

A

● As oxygen levels increase, the rate of decomposition increases
● As oxygen levels decrease, the rate of decomposition decreases

61
Q

Why can decomposition still occur in the absence of oxygen?

A

Some decomposers respire anaerobically

*However, the rate of decomposition is slower as anaerobic respiration produces less energy

62
Q

How does temperature affect the rate of decomposition?

A

Decomposers release enzymes:
● Rate highest at 50°C (optimum temperature for enzymes)
● Lower temperatures, enzymes work too slowly, rate decreases
● High temperatures, enzymes denature, decomposition stops

63
Q

How does soil water content affect the rate of decomposition?

A

Decomposers require water to survive:
● In moist conditions the rate of decomposition is high
● In waterlogged soils there is little oxygen for respiration so the rate of decomposition decreases

64
Q

What conditions are required to make compost?

A

Conditions that give a high rate of decomposition: plentiful supply of oxygen, warm, moist etc.

65
Q

Describe the methods of food storage used to slow down the rate of decomposition

A

● Stored in a fridge/freezer to slow down the activity of microbes
● Stored in airtight cans to prevent the entry of microorganisms
● High temperatures sterilise cans, destroying any bacteria
● Adding salt or sugar kills microbes (lose water by osmosis)
● Food kept dry to reduce the ability of microorganisms to survive

66
Q

What is an indicator species?

A

A species whose presence or absence in an environment provides indication of environmental conditions e.g. pollution levels

67
Q

What indicator species can be used to identify polluted water?

A

● Bloodworms ● Sludgeworms

adapted to live in polluted water

68
Q

What indicator species can be used to identify clean water?

A

● Freshwater shrimps ● Stonefly

sensitive to oxygen concentrations so can only survive in clean water

69
Q

What indicator species can be used to identify clean air?

A

Blackspot fungus found on rose leaves

sensitive to sulfur dioxide concentrations so can only survive in clean air

70
Q

What are lichens used for?

A

Used to monitor air pollution

71
Q

How can lichens indicate air pollution?

A

● Sensitive to the concentration of sulfur dioxide
● Different types of lichens grow in different levels of air pollution e.g. bushy lichens grow in cleaner air than crusty lichens
● Abundance and distribution of lichens indicate levels of pollution

72
Q

Evaluate the use of indicator species as a measure of pollution

A

● Cheaper and simpler
● Used to monitor pollution levels over long periods of time

However…
● Less accurate than non-living indicators e.g. electronic meters
● Do not provide a definitive figure for pollution levels

Gcse Biology (14 decks)

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