Unit 6.5- Ecosystems Flashcards Preview

A Level (A2) OCR Biology > Unit 6.5- Ecosystems > Flashcards

Flashcards in Unit 6.5- Ecosystems Deck (21)
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1
Q

Habitat definition:

A

The place where an organism lives

2
Q

Population definition:

A

All of the organisms of one species, who live in the same place at the same time and who can breed together

3
Q

Community definition:

A

All of the populations of different species, who live in the same place at the same time and who can interact with each other

4
Q

Niche definition:

A

The role of an organism

5
Q

Biotic factors in an ecosystem:

A
  • Producers
  • Consumers
  • Decomposers
6
Q

Abiotic factors lethal at both extremes:

A
  • PH

- Temperature

7
Q

Abiotic factors lethal at one extreme:

A

-Level of pollutants

8
Q

Cyclic changes definition (ecosystem):

A

These changes repeat themselves in a rhythm. e.g. tides

9
Q

Directional changes definition (ecosystem):

A

Changes that go in one direction. They tend to last longer than the lifetime of organisms within the ecosystem e.g. erosion

10
Q

Unpredictable/ erratic changes definition (ecosystem):

A

Changes that have no rhythm or constant direction. e.g. the effects of lighting or hurricanes

11
Q

What is the equation for ecological efficiency?

A

(Biomass at higher trophic level / biomass at lower trophic level) x 100

12
Q

How can net primary productivity be increased?

A
  • Drought resistant crops
  • Greenhouses
  • Crop rotation
  • Pesticides (insects)
  • Fungicides (fungal infections)
  • Herbicides (weeds)
13
Q

How can secondary productivity be improved?

A
  • Harvesting animals just before adulthood, when the largest proportion of their energy is used for growth
  • Selective breeding
  • Antibiotics
  • Supply animals with food so they don’t waste energy getting it themselves
14
Q

Climax community definition:

A

The final stable community that exists after the process of succession has occurred

15
Q

Deflected succession definition:

A

When succession is stopped or interfered with, e.g. grazing or when a lawn is mowed

16
Q

Pioneer species definition:

A

The species that begun the process of succession, often colonising an area as the first livings things there

17
Q

Succession definition:

A

Progressive change in a community of organisms over time

18
Q

In the nitrogen cycle, what are the nitrogen fixing processes?

A
  • N2 in air fixed by RHIZOBIUM bacteria in leguminous plants
  • N2 in air fixed by free living bacteria in the soil e.g. AZOBACTER
  • N2 in air fixed by Haber process. Turned into ammonium and nitrate ions in fertiliser
  • N2 in air fixed by lighting. Turns into nitrogen oxide and then nitrates in the soil
19
Q

In the nitrogen cycle, what are the nitrification processes?

A

In soil:

  • Ammonium oxidated by bacteria e.g. NITROSOMONAS into nitrites
  • Nitrites oxidised by bacteria e.g. NITROBACTER into nitrates
20
Q

In the nitrogen cycle, what are the decomposition and ammonification processes?

A
  • Organic nitrogen in soil into ammonium

- Urea into ammonium

21
Q

In the nitrogen cycle, what are the denitrifyign processes?

A

-Nitrates in soil denitrified by bacteria into N2 in air