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Biology OCR GCSE > B4 Ecosystems > Flashcards

B4 Ecosystems Flashcards

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1
Q

Ecosystem

A

All living organisms and physical conditions in the area

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2
Q

Community

A

All the organisms in the ecosystem

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3
Q

Habitat

A

Area where an organism lives

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4
Q

Consumers

A

Organisms that eat others to gain energy

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5
Q

Decomposers

A

Special group of consumers that feed on dead or decaying material

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6
Q

Population

A

Total number of organisms of each species

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7
Q

Producers

A

Organisms that make their own food by photosynthesis

Green plants
Algae
Phytoplankton

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8
Q

Interdependence

A

Organisms that rely upon each other to survive

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9
Q

Abiotic factors that affect communities

A

Moisture levels – water is required by all living things
Temperature – affects the rate of chemical reactions in organisms
Light intensity – necessary for photosynthesis - change in light over seasons can affect flowering of certain plants too
Soil type – level of nutrients and ability to hold water, pH
Gas levels – humidity and temperature can affect the amount of oxygen in the air
Fire – can be devastating for some organisms, but necessary for others (e.g. Australian plants/Scotish gorse/Heathland control)

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10
Q

Biotic factors that affect communities

A

Number of predators
Food availability
Disease
Human activity

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11
Q

Types of interdependence

A

Predation
Mutualism
Parasitism

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12
Q

Commensalism

A

When one organism benefits from another organism, which is unaffected

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13
Q

Competition

A

Two or more organisms fight over a resource
Can occur between different species, or within same species or family

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14
Q

Parasitism

A

When one organism lives on or in another organism and takes nutrients from (feeds off) the other organism
Benficial to parasite but detrimental to host

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15
Q

Mutualism

A

When 2 organisms living closely together both benefit from each other
Both depend on each other

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16
Q

4 things animals compete for

A

Water
Space
Mates
Food

17
Q

4 things plants compete for

A

Water
Space
Light
Minerals

18
Q

Primary consumer

A

Organism that feeds on producers

19
Q

Secondary consumer

A

Organism that feeds on primary consumers

20
Q

Biomass

A

DRY mass of all living organisms in an area

21
Q

Why dry mass is used for biomass

A

Wet mass varies because volume of water in organism varies

22
Q

Efficiency of biomass transfer

A

Efficiency = (energy transferred / total energy available) x 100

(As a percentage)

23
Q

Why biomass transfers are not 100% efficient

A

Energy is lost through:
Egestion (removal of faeces)
Excretion (removal of urine)
Respiration
Inedible bones / hair / shells / teeth / spines

If there was no wastage, all of the energy that entered a trophic level would be used for growth

24
Q

How efficiency of biomas transfers affect number of levels in a biomass pyramid

A

The less efficient the transfers,
lower the number of trophic levels and fewer organisms in higher trophic levels

25
Q

3 molecules which are cycle through ecosystems

A

Oxygen
Carbon dioxide
Water

26
Q

How water is cycled through an ecosystem

A

Water evaporates from rivers and lakes and from transpiration
Water condenses as clouds
Water is returned through precipitation

27
Q

How carbon is cycled through an ecosystem

A

Carbon dioxide is taken in by plants through photosynthesis
Respiration releases carbon dioxide
Decomposition releases carbon dioxide
Combustion releases carbon dioxide

28
Q

How nitrogen is cycled through an ecosystem

A

Nitrogen is fixed by lightening and nitrogen-fixing bacteria

Denitrifying bacteria release nitrites in soil into nirtogen in the air

Denitrifying bacteria covert nitrates in soil into nitrites, and nitrites to ammonia

Nitrifying bacteria convert ammonia in soil into nitrites, and nitrites to nitrates

Nitrates in soil taken up by plants and combined with carbohydrates to make plant proteins
Plant proteins either eaten by other animals to form animal protien or die and decompose to release ammonia into soil
Animals excrete ammonia and die and decompose to release ammonia into soil

29
Q

Why recycling in ecosystems is necessary

A

To create a continuous flow of nutrients
To provide fresh water

30
Q

How a descrease in oxygen availabilty would affect rate of decomposition

A

Lack of oxygen causes micro-organisms to respire anaerobically
Anaerobic decay is slower that aerobic decay

31
Q

How would a descrease in water availabilty affect the rate of decomposition

A

Decomposing microorganisms need water for chemical processes
The less water available, slower the rate of these processes

32
Q

How a change in temperature would affect the rate of decomposition

A

Decrease in temperature slows rate of decomposition reactions
Large increase in temperature would denature enzymes, slowing or even stopping decomposition

33
Q

Difference between a detritivore and a decomposer

A

Detritivores are small animals that speed up decomposition by shredding DOM into very small pieces creating a larger surface area for decomposers to work upon
Detritivores use external digestion to break DOM down

Decomposers are microorganisms that breakdown dead organic matter and organic waste upon a microscopic level
Decomposers use external digestion

34
Q

Nitrogen cycle - bacteria

A

Bacteria are essential for nitrogen cycle

Decomposers - break down organic matter contain nitrogen, back into nitrogen accessible in soil
Denitrifying bacteria - break down nitrates into nitrogen gas, remove nitrates from soil
Nitrifying bacteria - break down ammonia into nitrates, add nitrates to soil
Nitrogen-fixing bacteria in root nodules - convert nitrogen gas into nitrates

35
Q

Nitrogen cycle diagram

A

According to this diagram, plants absorb nitrates

————————> Primary consumers feed ———————> Death and excretion————————
| v
Nitrogen fixing by root nodule bacteria <— Nitrogen gas in the air Proteins and urea
^ | ^ v
Absorption by roots v | Decomposers (soil bacteria)
| Nitrogen fixing bacteria or lightning Breakdown by denitrifying bacteria |
^ | ^ |
| v | v
L_________________________________________ Nitrates in the soil < Oxidation by nitrifying bacteria < Ammonia

36
Q

How much of the atmosphere is composed of nitrogen gas

A

78%

37
Q

Main difference between denitrification and other three steps of nitrogen cycle

A

Denitrification changes nitrogen into a gaseous form

Biology OCR GCSE (16 decks)

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