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LGS GCSE OCR Biology A - Aayan 🔫🔫 > B4 Ecosystems > Flashcards

B4 Ecosystems Flashcards

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1
Q

Define Ecosystem.

A

All the living organisms and physical conditions in the area.

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2
Q

Define Community.

A

All of the organisms in the ecosystem.

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3
Q

Define Habitat

A

Area where an organism lives

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4
Q

Define Consumers.

A

Organisms that eat others to gain energy.

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5
Q

Define Decomposers.

A

A special group of consumers that feed on dead or decaying material.

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6
Q

Define Population.

A

Total number of organisms of each species.

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7
Q

Define Producers.

A

Organisms that make their own food by photosynthesis.

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8
Q

Define the term ‘interdependence’.

A

Interdependence relates to living things that rely upon each other to survive.

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9
Q

State four 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

State four biotic factors that affect communities.

A
  • Number of predators
  • Food availability
  • Disease
  • Human activity
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11
Q

What are the three types of interdependence?

A
  • Predation
  • Mutualism
  • Parasitism
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12
Q

Define commensalism.

A

When one organism benefits from another organism, which is unaffected.

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13
Q

Define competition.

A

When two organisms fight over a resource. Can occur between different species, or within the same species or family.

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14
Q

What is parasitism?

A
  • When one organism lives on or in another organism and takes nutrients from (feeds off) the other organism.
  • This is benficial to the parasite but detrimental to the host.
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15
Q

Wht is mutualism?

A
  • When two organisms living closely together both benefit from each other.
  • Two organisms that depend on each other
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16
Q

Give four things animals compete for.

A
  1. Mates
  2. Space
  3. Food
  4. Water
17
Q

Give four things plants compete for.

A
  1. Light
  2. Water
  3. Minerals
  4. Space
18
Q

What is a primary consumer?

A

An organism that feeds on producers.

19
Q

What is a secondary consumer?

A

An organism that feeds on primary consumers.

20
Q

What is biomass?

A

The dry mass of all of the living organisms in an area.

21
Q

Why is dry mass used for biomass?

A

Because the wet mass varies as the amount of water in the organism varies.

22
Q

How do you calculate the efficiency of biomass transfer?

A

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

23
Q

Why are biomass transfers not 100% efficient?

A

Energy is lost through:

  • Egestion (removal of faeces)
  • Excretion (removal of urine)
  • Respiration
  • Inedible bones / hair / shells / teeth / spines
24
Q

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

A

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

25
Q

Name three molecules which are cycle through ecosystems.

A
  1. Oxygen
  2. Carbon dioxide
  3. Water
26
Q

Describe 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

Describe how carbon is cycled through an ecosystem.

A
  1. Carbon dioxide is fixed through photosynthesis
  2. Respiration releases carbon dioxide
  3. Decomposition releases carbon dioxide
  4. Combustion releases carbon dioxide
28
Q

Describe how nitrogen is cycled through an ecosystem.

A
  1. Nitrogen is fixed by lightening and nitrogen-fixing bacteria
  2. Denitrifying bacteria release nitrites in soil into nirtogen in the air.
  3. Denitrifying bacteria covert nitrates in soil into nitrites, and nitrites to ammonia.
  4. Nitrifying bacteria convert ammonia in soil into nitrites, and nitrites to nitrates.
  5. Nitrates in soil taken up by plants and combined with carbohydrates to make plant proteins.
  6. Plant proteins either eaten by other animals to form animal protien or die and decompose to release ammonia into soil.
  7. Animals excrete ammonia and die and decompose to release ammonia into soil.
29
Q

Why is recycling in ecosystems necessary?

A
  • To create a continuous flow of nutrients
  • To provide fresh water
30
Q

How would a descrease in oxygen availabilty affect the 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
  • Te less water available, the slower the rate of these processes
32
Q

How would a change in temperature affect the rate of decomposition?

A
  • A decrease in temperature slows the rate of decomposition reactions
  • A large increase in temperature would denaute enzymes, slowing or even stopping decomposition
33
Q

What is the difference between a decomposer and a detritivore?

A
  • Decomposers are microorganisms that breakdown dead organic matter (DOM) and organic waste upon a microscopic level
  • Decomposers use external digestion to break DOM down.
  • Detritivores are small animals that speed up decompositio by shredding DOM into very small pieces creating a larger surface area for decomposers to work upon.
  • Detritivores use internal digestion to break DOM down.
34
Q

Efficiency of Biomass Transfer

A

Only 3 - 4 levels as there will not be enough energy for a consumer to sustain themselves

LGS GCSE OCR Biology A - Aayan 🔫🔫 (22 decks)

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