Question
Forest fires are very common in the Amazon forest. A study was performed to see the relationship between forest fragmentation, fire and management
a. Describe one method that could have been used to estimate the population size of a given tree in a forest after fire damage had occurred. [3]
b. Outline how the edge effect can affect diversity in forests. [3]
The number of plants in two fields of approximately the same size was counted.
c. Compare and contrast the richness and the evenness of the two fields. [2]
▶️Answer/Explanation
Markscheme
ALTERNATIVE 1
a. transect through a given area
b. trees counted on transect
c. calculation of total population considering area
ALTERNATIVE 2
d. random sampling using quadrats
e. trees counted in quadrat
f. population calculated using area
ALTERNATIVE 3
g. GPS/Google Earth used to map individuals of a tree species
h. data base of data obtained
i. population density calculated using area
a. edge effect are the changes in community structures that occur at the boundary of two habitats
b. areas with small habitat fragments exhibit especially pronounced edge effects
c. edge species will always have a habitat
OR
edge biodiversity increases
d. if patches of forest are too small the non-edge species cannot find a habitat
e. «then» overall non-edge biodiversity is lower
a. same richness as they have the same number of species/total of individuals
b. field 1 has more evenness as more even distribution of numbers among the species
Accept correct use 2 of Simpson diversity index.
Question
b. Define indicator species. [1]
c. Indicator species may be affected by biomagnification. Discuss biomagnification using a named example of a pollutant. [3]
e. Determine whether islands are open or closed ecosystems. [1]
▶️Answer/Explanation
Markscheme
organism that is present/absent when specific environmental conditions exist
OR
organism used to assess a specific environmental condition
a. example eg: DDT / mercury / cadmium
b. substance accumulates in «fat» tissue/not excreted «when consumed»
c. contaminated organisms consumed «in large quantities» by higher level consumers
d. pollutant becomes more concentrated at each higher trophic level / through the food chain
e. some pollutants are more likely to be biomagnified «accumulate in fat tissue»
OR
some organisms are more likely to be affected by biomagnification than others
OR
biomagnification not the same at each trophic level
Only [2] if verified example not given.
closed because islands do not exchange matter/nutrients with surroundings
OR
open because islands do exchange matter/nutrients with surroundings
Question
The Vancouver Island marmot (Marmota vancouverensis) is a small rodent that is only found on Vancouver Island and is listed as critically endangered. Captive breeding and release programs for this species began in 1997 to attempt to restore population numbers on the island. The graph shows the causes of death of the marmots born in the wild and of those marmots released after being born and reared in captivity.
a.i. Distinguish between levels of predation in marmots born in the wild and those born in captivity. [1]
a.ii. Suggest reasons for the differences in predation. [2]
b. Distinguish between ex situ and in situ conservation of endangered species. [1]
▶️Answer/Explanation
Markscheme
predation was greater in those born in captivity ✔
a. the marmots have experience with/recognize predators ✔
b. parents shield them from predators
OR
parents teach them about predators ✔
c. those born in the wild are favoured in natural selection ✔
ex situ is in artificial environment, in situ is in natural environment ✔