1 | Page
ECOL111 - Population Biology Questions
and Correct Answers
13. Ecosystem services by cockles Ans: - Filtering out particulate
water/ bacteria through in/excurrent channels using siphons and
mucus from glands
- Fossils have 20-30 year record of sea ice conditions
- Food for birds, fish, marine mammals
- Sediment stabilisation through pseudofaeces deposit and
bioturbation
- Shell material isotope analysis used to show water conditions/
productivity
- Increase benthic production and benthic-pelagic coupling
13. Case studies of cockles Ans: - NY Harbour lost bivalves from
petroleum and fire in hudson river
- Dutch Wadden Sea decline in subtidal beds of cockles causing
collapse of eider duck population and loss of filtering
- Gulf of California reduced flow in Colorado River lead to bivalve
decline causing benthic productivity to decline
13. Causes of cockle decline Ans: - Nutrient pollution
- Diatom blooms and eutrophication (anoxic conditions)
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- Fires/ Petroleum
- Recruitment failure/ high mortality rates
- Interspecific competition with more tolerant species Macoma
balthica
13. Case Study of Fiordland (Doubtful Sound) Bivalve interactions
Ans: - Manapouri power station aided widespread decline of inner
fjord bivalves (none left in system, some in outer areas)
- Tunnel boring cause population isolation in fjords based on
estuarine circulation
- Prey based shifts in Jasus Edwardsii rock lobster due to lack of
bivalve prey
13. Management of bivalves Ans: Based on biomass growth rather
than ecological importance or role are ecosystem service provider
14. Population Ans: A group of organisms that have connectivity
across time and space
14. Difference between Open and Closed populations Ans: Closed
populations are when the members of the population are fixed (no
emi-/immigration) and are thus easier to predict population
increase and changes using predictive models.
Open populations are dynamic (not fixed) and immigration is
random and from unknown sources.
14. Example of Open Population Ans: Spiny Rock Lobsters (jasus
edwardsii) - highly migratory, planktonic stage with moults lasts to
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18 months and can travel 100,000kms with recruitment and
settlement location related to oceanographic conditions.
14. Example of closed population Ans: Kakapo originally ranged
through mainland NZ before decline from fragmented populations
(first indicator), changes in native tree masting and introduced
mammalian predators confined them to Codfish and a few other
protected islands.
14. Critical viable population size Ans: The smallest population
size in which a population can persist i.e. nearly reached in
Kakapo populations
14. Scales of distribution Ans: Local, (over)dispersed (can be
regular), random, clumped
14. Uses of population abundance data Ans: - Estimating
probability of population survival
- Estimating sustainable harvest
- Understanding populations in nature
- Assessing spread of a pest
- Calculating needs of managed populations
14. Population dynamics of tigers Ans: - Range gone from large
connected population to fragmented populations in insular chunks
- Habitat loss driver
- Loss of 35,000 to 5,000 tigers (Javan and Southern China extinct)
© 2025 All rights reserved
ECOL111 - Population Biology Questions
and Correct Answers
13. Ecosystem services by cockles Ans: - Filtering out particulate
water/ bacteria through in/excurrent channels using siphons and
mucus from glands
- Fossils have 20-30 year record of sea ice conditions
- Food for birds, fish, marine mammals
- Sediment stabilisation through pseudofaeces deposit and
bioturbation
- Shell material isotope analysis used to show water conditions/
productivity
- Increase benthic production and benthic-pelagic coupling
13. Case studies of cockles Ans: - NY Harbour lost bivalves from
petroleum and fire in hudson river
- Dutch Wadden Sea decline in subtidal beds of cockles causing
collapse of eider duck population and loss of filtering
- Gulf of California reduced flow in Colorado River lead to bivalve
decline causing benthic productivity to decline
13. Causes of cockle decline Ans: - Nutrient pollution
- Diatom blooms and eutrophication (anoxic conditions)
© 2025 All rights reserved
, 2 | Page
- Fires/ Petroleum
- Recruitment failure/ high mortality rates
- Interspecific competition with more tolerant species Macoma
balthica
13. Case Study of Fiordland (Doubtful Sound) Bivalve interactions
Ans: - Manapouri power station aided widespread decline of inner
fjord bivalves (none left in system, some in outer areas)
- Tunnel boring cause population isolation in fjords based on
estuarine circulation
- Prey based shifts in Jasus Edwardsii rock lobster due to lack of
bivalve prey
13. Management of bivalves Ans: Based on biomass growth rather
than ecological importance or role are ecosystem service provider
14. Population Ans: A group of organisms that have connectivity
across time and space
14. Difference between Open and Closed populations Ans: Closed
populations are when the members of the population are fixed (no
emi-/immigration) and are thus easier to predict population
increase and changes using predictive models.
Open populations are dynamic (not fixed) and immigration is
random and from unknown sources.
14. Example of Open Population Ans: Spiny Rock Lobsters (jasus
edwardsii) - highly migratory, planktonic stage with moults lasts to
© 2025 All rights reserved
, 3 | Page
18 months and can travel 100,000kms with recruitment and
settlement location related to oceanographic conditions.
14. Example of closed population Ans: Kakapo originally ranged
through mainland NZ before decline from fragmented populations
(first indicator), changes in native tree masting and introduced
mammalian predators confined them to Codfish and a few other
protected islands.
14. Critical viable population size Ans: The smallest population
size in which a population can persist i.e. nearly reached in
Kakapo populations
14. Scales of distribution Ans: Local, (over)dispersed (can be
regular), random, clumped
14. Uses of population abundance data Ans: - Estimating
probability of population survival
- Estimating sustainable harvest
- Understanding populations in nature
- Assessing spread of a pest
- Calculating needs of managed populations
14. Population dynamics of tigers Ans: - Range gone from large
connected population to fragmented populations in insular chunks
- Habitat loss driver
- Loss of 35,000 to 5,000 tigers (Javan and Southern China extinct)
© 2025 All rights reserved
