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Biology A2 > Ecosystems, 6.5 > Flashcards

Ecosystems, 6.5 Flashcards

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1
Q

What is an ecosystem?

A

Group of living and non-living things and the interrelationships between them

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2
Q

What is a habitat?

A

Place where an organism lives

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3
Q

What is a population?

A

Organisms of one species who live in the same place at the same time and can interbreed

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4
Q

What is a community?

A

Populations of different species who live in the same place at the same time and can interact

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5
Q

What is a niche?

A

The role of an organism within its habitat

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6
Q

What are biotic factors?

A

Living organisms in an ecosystem that affect each other

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7
Q

Who are the producers?

A

Plants, supply chemical energy

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8
Q

Who are the consumers?

A

Primary consumers - herbivores. Secondary consumers - carnivores

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9
Q

What is the role of decomposers?

A

Feed on waste material and dead organisms

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10
Q

What are abiotic factors?

A

Non-;living components of an ecosystem

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11
Q

What are some examples of abiotic factors?

A

pH. Relative Humidity. Temperatures. Concentration of pollutants. Weather eg storms.

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12
Q

Why are ecosystems described as dynamic?

A

Because they change

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13
Q

What are cyclic changes?

A

Changes that repeat themselves in a rhythm eg waves, the tide

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14
Q

What are directional changes?

A

Change goes in one direction and lasts longer than the lifetimes of the organisms in the ecosystems

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15
Q

What are unpredictable/erratic changes?

A

No rhythm or direction eg effects of a hurrican

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16
Q

In what ways might organisms respond to changes?

A

Some animals change their fur colour in the winter. Trees shed their leaves.

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17
Q

What is biomass transfer?

A

Transfer of biomass from one trophic level to another

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18
Q

What is the trophic level?

A

The level at which an organism feeds in a food chain

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19
Q

What is the role of plants ?

A
  • Capture energy
  • Produce glucose
  • Products of photosynthesis incorporated into tissues and organs
  • Mineral ions taken up through the roots
  • When a plant is eaten its biomass is consumed by a primary consumer
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20
Q

Why is some biomass lost at each stage of a food chain?

A
  • Organisms need energy to carry out life processes
  • Some energy converted to heat
  • Materials lost in CO2 and water
  • Biomass also lost in dead organisms or waste material
  • Also include bones and hair which cant be digested.
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21
Q

In a pyramid of biomass what is does each bar represent?

A

The area of each bar is proportional to the number of individuals

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22
Q

How does an ecologist calculate the efficiency of biomass transfer?

A
  1. Ecologist collects all the organisms and outs them in an oven at 80degrees
    - Until all the water has been evaporated
    - once the mass stops reducing the water has been removed
    - Destructive to the ecosystem being studied
    - Ecologists often just measure wet mass
23
Q

What is meant by productivity?

A

Rate of production of new biomass by producers

24
Q

What is gross primary productivity?

A

Rate at which plants convert light energy to chemical energy

25
Q

Why is gross primary productivity inefficient?

A

Energy is lost when the plant respires. Only a small proportion of energy from the sun remains to enter the food chain

26
Q

What can be done to help plants grow and make energy conversion more efficient?

A
  • Light levels maintained under light banks
  • Irrigating crops and drought resisting strains
  • Grow plants in a greenhouse
  • Crop rotation, more nutrients available
  • Pesticides, stop insects
27
Q

Why don’t primary consumers make full use plants biomass?

A

Much of it is respired so only a small amount contributing to increase biomass

28
Q

What methods are there of increasing the amount of energy from primary consumers?

A
  • Young animals use more energy in growth so harvest just before adulthood
  • Selective breeding produces breeds with high growth rates
  • Animals may be treated with antibiotics
  • Mammals lose energy by finding food but none is lost by allowing them to graze
29
Q

How are dead and waste organic materials decomposed?

A

By decomposers such as bacteria and fungi. They feed saprotrophically.

30
Q

How do decomposers feed on waste material?

A
  1. Secrete enzymes onto dead and waste material
  2. Enzymes digest material into small molecules which are then absorbed into the saprotrophs
  3. Molecules are stored or respired
31
Q

What are the 3 different stages of recycling nitrogen?

A

Nitrogen fixation. Ammonification and nitrification. Denitrification.

32
Q

What is Nitrogen Fixation?

A
  • Makes up 79% of the atmosphere
  • Impossible for plants to use directly
  • Need a supply of fixed nitrogen
  • Occur during lightning strikes, haber process or nitrogen fixing bacter
33
Q

What can the the bacteria Rhizobium do?

A

Provide the plant with nitrogen and receive carbon compounds - mutualistic relationship

34
Q

What is ammonification and nitrification?

A
  • Ammonium ions are release through ammonification by bacteria involved in purtrefaction of proteins found dead organic matter
  • Some chemoautrophic bacteria obtain energy by oxidising ammonium ions to nitrites
  • Others obtain energy by oxidising nitrites to nitrates
  • Nitrates can be absorbed by plants to make nucleotide bases and amino acids
35
Q

What is denitrification?

A
  • Bacteria can convert nitrates back into nitrogen gas
  • When bacteria are involved growing under anaerobic conditions eg water logged soils
  • Uses nitrates as a source of oxygen
  • So produces nitrogen gas and nitrous oxide
36
Q

Draw a diagram of the carbon cycle

A
  • Animals: feed respire, death, excretion, fossils
  • Detritus and waste: death, decomposition, produced CO2
  • Fossil fuels: fossilization, combustion
  • Plants: photosynthesis, respiration, eaten, death
37
Q

What is succession?

A

Progressive change in a community over time

38
Q

What is primary succession?

A

Development of communities from bare rock

39
Q

What are the stages of primary succession?

A
  1. Algae and lichens begin to live on bare rock - pioneer community
  2. Erosion of the rock and the build up of dead organic material produce nutrients and soil for larger plants to grow - these replace the algae and lichen
  3. Larger plants continue to succeed smaller plants until a final stable community is reached
40
Q

What is the climax community?

A

A stable final community often woodland

41
Q

What is secondary succession?

A

Takes place on a previously colonized but damaged habitat

42
Q

Describe succession on sand dunes.

A
  1. Embryo dune -pioneer species eg sea rocket, prickly saltwort - just above the high water mark, harsh, salty
  2. Wind lows sand to form mobile dune - pioneer species eg marram grass, plants die and decay providing nutrients
  3. Semi-fixed dune - intermediate colonies, restharrow, dne moss, grasses - stabilises the sand
  4. Fixed Dune - sea purge and marram grass grow, traps more sand, stability and nutrients
  5. Sand dune and nutrients build up and other plants colonise
  6. Scrub
  7. Climax community (forest) - Final endpoint of succession, stable self-replication community, oak ash, woodland, trees
43
Q

Why are sandunes conserved?

A

Multitude of habitats supporting specialised plant species

44
Q

What are they doing to conserve the sand dunes?

A
  • Prevent beach cleaning of seaweed
  • Scrub clearance
  • Removal of forestry plantation
  • Grazing
  • Fencing to stop cattle
  • Beach nourishment
45
Q

What is zonation?

A

Change in plant and animal communities over space

46
Q

What is deflected succession?

A

Happens when succession is stopped or interfered with for example agriculture

47
Q

What is sampling?

A
  • Small portions from a habitat

- Representative of the larger habitat

48
Q

What are quadrats?

A

Small sampling square

49
Q

How can we use quadrats for sampling?

A
  • Distribution (presence of absense), 50% of the plant in the quadrat to count
  • Abundance (number of individuals) of each species estimated or counted
50
Q

How can we place quadrats?

A
  • Randomly, random numbers

- At regular intervals across the habitat

51
Q

How many samples should you take?

A
  • Plot a cumulative frequency against quadrat number

- When curve levels off tells you how many quadrats to use

52
Q

What does a transect measure?

A

Changes across a habitat

53
Q

What is a line transect?

A

At regular intervals make a note of the species touching the tape

54
Q

What is a belt transect?

A

At regular intervals place a quadrat

Biology A2 (13 decks)

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