6.5 ECOSYSTEMS

Question 1

Define succession

Answer 1

• The progressive change in a community of organisms over time

Question 2

Define pioneer species

Answer 2

• Species that begin the process of succession by colonising an area as the first living organism there

Question 3

Define climax community

Answer 3

• The final stable community that exists after succession has occurred

Question 4

Define deflected succession

Answer 4

• When succession is interfered with or stopped preventing a stable climax community

Question 5

Define primary succession

Answer 5

• Succession starting from a previously uninhabited environment

Question 6

Define secondary succession

Answer 6

• Succession restarting from a disrupted environment

Question 7

State three factors that explain why secondary succession is easier/faster than primary succession

Answer 7

• Left over seeds in soil
• Left over organisms in soil
• Left over bacteria in soil

Question 8

State three reasons why deflective succession happens

Answer 8

• human activity (agriculture/urbanisation/pollution)
• abiotic factors (wave action/fires/shape of landscape)
• biotic factors (trampling/animal eating)

Question 9

State three changes simple organisms undergo before and after succession to become complex organisms

Answer 9

• From autotrophs to auto & heterotrophs
• From minimal nutrition requirements to complex nutrition requirements
• From extremophiles to being sensitive to environmental change

Question 10

State four changed to the community after succession

Answer 10

• Increase in interdependence
• Increase in productivity
• Increase in biodiversity
• Increase in abiotic/environmental favourability

Question 11

Describe the term ecosystem

Answer 11

• A community and the abiotic components of an environment
• Range in size
• Dynamic

Question 12

State what biotic and abiotic factors influence in an ecosystem

Answer 12

• the carrying capacity of a population
• the distribution of populations

Question 13

Describe five factors that are abiotic

Answer 13

1) Light (affects photosynthetic organisms)
2) Temperature (affects metabolic rates)
3) pH (affects enzymes)
4) Water availability (affects photosynthesis and temp fluctuations)
5) Topography of landscape (affects light exposure)
6) Oxygen concentration (affects respiration

Question 14

Describe three factors that are biotic

Answer 14

1) Intra/Interspecific competition
2) Pathogenic disease
3) Predator-prey interactions

Question 15

Define biotic

Answer 15

• Living

Question 16

Define abiotic

Answer 16

• Non-living

Question 17

Describe the three types of dynamic changes in an ecosystem

Answer 17

1) Cyclic changes (seasonal temperature changes/predator-prey cycles)
2) Directional changes (erosion/sand deposit in lakes)
3) One-off changes (natural disasters)

Question 18

Define autotrophs

Answer 18

• Organism that makes its own food

Question 19

Define heterotrophs

Answer 19

• Organisms that eat other organisms for food

Question 20

State three reasons why there is not 100% efficiency of energy transfer in food chains

Answer 20

• Respiration
• Organism isn’t fully eaten
• Not all of the organism is digested so is faeces

Question 21

State the efficiency formula for biomass transfer

Answer 21

Question 22

List the types of organisms and their relative energy content in a basic food chain

Answer 22

Producer (1000kJ) → Primary consumer (100kJ) → Secondary consumer (20kJ) → Tertiary consumer (5kJ)

Question 23

State why the first energy transfer in a food chain is relatively lower than thesecond energy transfer

Answer 23

• Its harder to digest plant tissue
• Its easier to digest meat

Question 24

Define gross primary productivity (GPP)

Answer 24

• The rate of conversion of light energy to chemical energy in producers during photosynthesis

Question 25

Define net primary productivity (NPP)

Answer 25

• The rate of conversion of light energy to chemical energy in producers during photosynthesis, MINUS the chemical energy used in respiration

Question 26

Define gross secondary productivity (GSP)

Answer 26

• The rate of chemical energy transfer to consumer from previous trophic level

Question 27

Define net secondary productivity (NSP)

Answer 27

• The rate of chemical energy transfer to consumer from previous trophic level, MINUS the chemical energy used in respiration

Question 28

State what the net primary/secondary productivity tells us

Answer 28

• This is the amount of energy actually stored as biomass

Question 29

State five ways increasing primary productivity

Answer 29

1) Artificial lighting
2) Glasshouse
3) Selective breeding
4) Genetic modification for higher yeilds/pest resistance
5) Fertilisers

Question 30

State six ways increasing secondary productivity

Answer 30

1) Restrict movement
2) Shelter from predators
3) Insulation
4) High nutrient diet
5) Selective breeding

Question 31

Draw the nitrogen cycle

Answer 31

Question 32

Define nitrogen fixation and which bacteria does this

Answer 32

• Rhizobium bacteria and Azotobacter bacteria

Question 33

Define ammonification

Answer 33

Question 34

Define nitrification and which bacteria does this

Answer 34

1) Nitrosomonas bacteria
2) Nitrobacter bacteria

Question 35

Define denitrification and which bacteria does this

Answer 35

• Denitrifying bacteria

Question 36

Draw the carbon cycle

Answer 36

Question 37

Describe the process of primary succession on bare rock

Answer 37

1) Arrival of seads/spores on bare rock as a pioneer community
2) Pioneer community have specific adaptations (e.g nitorgen fixation)
3) Intermediate community forms via moss/herbs species as there is
4)

Question 38

Describe the process of secondary succession on sand dunes