Topic 10.1 The nature of ecosystems

Question 1

Define ecosystem

Answer 1

an environment including all the living organisms interacting within it, the cycling of nutrients and the physical and chemical environment in which the organisms are living

Question 2

Define habitat

Answer 2

the place where an organism lives e.g. a stream, tropical rainforest or sand dune

Question 3

Define population

Answer 3

a group of organisms of the same species, living and breeding together in a habitat

Question 4

Define microhabitat

Answer 4

a small area of a habitat e.g. a fig on a tree may be home to a fig wasp

Question 5

Define community

Answer 5

all the populations of all the different species of organisms living in a habitat at any one time

Question 6

Define niche

Answer 6

the role of an organism in the community

Question 7

Define abiotic factors

Answer 7

non-living elements of the habitat of an organism

Question 8

Give examples of abiotic factors

Answer 8

• sunlight
• temperature
• rainfall
• drainage and pH of soil
• oxygen availability

Question 9

Define biotic factors

Answer 9

living elements of a habitat that affect the ability of a group of organisms to survive there

Question 10

Give examples of biotic factors

Answer 10

• predators
• suitable prey
• disease

Question 11

Define biosphere

Answer 11

all of the areas of the surface of the earth where living organisms survive

Question 12

Define biomes

Answer 12

the major ecosystems of the world

Question 13

Define succession

Answer 13

the process by which the communities of organisms colonising an area change over time

Question 14

Define climax community

Answer 14

a self-sustaining community with relatively constant biodiversity and species range. it is the most productive group of organisms that a given environment can support long term

Question 15

What does primary succession start with?

Answer 15

an empty inorganic surface such as bare rock or a sand dune

Question 16

Describe the stages of succession

Answer 16

1) Colonisation: species grow that are capable or surviving difficult conditions e.g. bare rock. they begin to break down rock and add organic matter
2) Pioneer species: these are able to grow when the colonisers have made conditions more hospital
3) Pioneer species produce soil as dead material accumulates which allows large herbaceous plants to outcompete pioneers
4) Shrubs and bushes can be supported when soil becomes deep enough
5) A climax community forms when the largest plants are able to grow . no further succession

Question 17

Define succression

Answer 17

series of changes that occur to the composition of species in the community of organisms present in an area over a period of time

Question 18

Define plagioclimax

Answer 18

a climax community which is partly the result of human intervention e.g. humans changing the landscape by adding grazing animals that prevent the growth of larger plant species

Question 19

Define edaphic factors

Answer 19

relate to the structure of the soil

Question 20

Define leaching

Answer 20

the loss of minerals from soil as water passes through rapidly

Question 21

How does light affect population size?

Answer 21

• plants dependent on light for photosynthesis
• animals affected indirectly as a result of plant distribution
• seasonal light changes also affect reproductive patterns due to circadian rhythms

Question 22

What does secondary succession start with?

Answer 22

begins on existing soil that is clear of vegetation e.g. after fires and floods

Question 23

How are plants adapted to cope with low levels of light?

Answer 23

• reproduce early to avoid shade from larger plants
• extra chlorophyll
• different ratio of photosynthetic pigments that are sensitive to lower levels of light
• having very large leaves

Question 24

How does temperature affect populations?

Answer 24

• affects enzyme-controlled reactions

- most organisms have a limited range in which they can reproduce successfully

Question 25

What abiotic factors affect populations?

Answer 25

• temperature
• light
• wind and water currents
• water availability
• oxygen availability
• edaphic factors (soil structure and mineral content)

Question 26

What is the affect of wind and water currents on organisms in a habitat?

Answer 26

• direct effect
• increases water loss from the body
• can destroy habitats
• organisms must flow with the current, be strong swimmers or attach to a surface

Question 27

What affects water availability on land?

Answer 27

• amount of precipitation
• rate of evaporation
• edaphic factors e.g. drainage through soil

Question 28

What is the effect of a decrease or increase in water availability on populations?

Answer 28

decrease: organisms die unless specially adapted
increase: increase in population size

Question 29

Give examples of where water availability may be low

Answer 29

• if temp of water rises or it becomes stagnant

- waterlogged soil (no longer aerated)

Question 30

What biotic factors effect populations?

Answer 30

• predation
• finding a mate
• territory
• parasitism and disease

Question 31

Define intraspecific competition

Answer 31

competition between members of the same species for a limited resource

Question 32

Define interspecific competition

Answer 32

occurs when different species within a community compete for the same resources