EcologyIB Environmental Systems and Societies HL: Topic test

20 questions, 54 marks

IB Environmental Systems and Societies HL

Ecology topic test

Total 54 marks

Name

Class

Date

1
On rocky shores in Scotland, two species of barnacle live at different heights. Chthamalus stellatus is found mainly on the upper shore, which is covered by the sea only at high tide. Balanus balanoides is found mainly on the lower shore. When researchers removed Balanus from the lower shore, Chthamalus was able to survive and grow there. When they removed Chthamalus from the upper shore, Balanus did not survive there.
(a)
Which factor most likely prevents Balanus from living on the upper shore?
[1 mark]
ACompetition from Chthamalus
BPredation by dog whelks
CDrying out during long periods of exposure to air
DThe pH of the soil
(b)
Which interaction best describes the relationship between the two species on the lower shore?
[1 mark]
AInterspecific competition, in which Balanus outcompetes Chthamalus
BMutualism, in which both species benefit
CParasitism, in which Balanus feeds on Chthamalus
DHerbivory, in which Chthamalus feeds on Balanus
(c)
Explain why Chthamalus is found mainly on the upper shore even though it can survive on the lower shore.
[2 marks]
Total for question 1: 4 marks
2
Estimates of average net primary productivity (NPP) include about 2 200 g of biomass per square metre per year in tropical rainforest and about 125 g per square metre per year in the open ocean. The rainforest has a warm, wet climate and high light levels all year. The surface waters of the open ocean receive light but are often low in dissolved nitrate and phosphate.
(a)
Which statement correctly defines net primary productivity?
[1 mark]
AThe total light energy absorbed by the producers
BThe gain in biomass by consumers from the food they eat
CThe total mass of producers present in an area at one time
DThe rate at which producers gain biomass after losses through cellular respiration
(b)
Why is net primary productivity described as the basis of food chains?
[1 mark]
AIt is the energy lost as heat by producers
BIt is the quantity of carbon compounds sustainably available to primary consumers
CIt measures the number of consumers an ecosystem contains
DIt is the energy used by producers in cellular respiration
(c)
Suggest two reasons why the NPP of the open ocean is much lower than that of tropical rainforest.
[2 marks]
Total for question 2: 4 marks
3
A wheat farmer in the Punjab region of India applies nitrogen fertiliser made by the Haber process to her fields. Her neighbour grows beans in rotation with wheat and ploughs the bean plant remains into the soil. In both fields the soil contains bacteria that change nitrogen compounds from one form to another. After heavy irrigation, parts of the farmland become waterlogged.
(a)
Outline the roles of bacteria in the nitrogen cycle in these fields.
[3 marks]
(b)
Evaluate the use of Haber process fertiliser compared with growing beans in rotation as a way of supplying nitrogen to crops.
[4 marks]
Total for question 3: 7 marks
4
The Congo Basin in central Africa lies on the equator and is covered by tropical rainforest, while the Sahara Desert lies about 20° to 30° north of the equator. Climate models predict that, as the planet warms, the boundaries between biomes will shift. Ecologists also point out that in parts of the British Isles, where climate alone would support temperate deciduous forest, the land is mostly farmland, moorland and towns.
(a)
Explain how the tricellular model of atmospheric circulation and abiotic factors determine the distribution of terrestrial biomes.
[6 marks]
(b)
Discuss why the biome predicted by the climate of an area may not develop there, and how global warming may change the distribution of biomes.
[6 marks]
Total for question 4: 12 marks
5
Since the late 2000s, oyster hatcheries along the Pacific coast of the USA have lost large numbers of oyster larvae. Upwelling brings cold deep water to the surface that holds high levels of dissolved carbon dioxide absorbed from the atmosphere over decades. The larvae must build thin shells of calcium carbonate in their first two days of life. Hatcheries now monitor the chemistry of the seawater and adjust it.
(a)
What happens to the pH of seawater when more carbon dioxide dissolves in it?
[1 mark]
AIt rises because carbonates form
BIt falls because carbonic acid forms
CIt stays the same because oceans cannot change
DIt rises because oxygen is released
(b)
Over millions of years, the calcium carbonate shells of dead marine organisms can become part of which carbon store?
[1 mark]
AThe atmosphere
BSoil humus
CDissolved carbon dioxide in surface water
DLimestone in the lithosphere
(c)
Explain how ocean acidification harms oyster larvae.
[2 marks]
Total for question 5: 4 marks
6
The resident killer whales (orcas) of the Salish Sea, off British Columbia and Washington State, carry some of the highest concentrations of polychlorinated biphenyls (PCBs) recorded in marine mammals. PCBs were banned in the 1970s and 1980s, but they do not break down easily and still enter coastal waters from contaminated sediments. The orcas eat mainly Chinook salmon, which feed on smaller fish, which feed on zooplankton.
(a)
Which term describes the build-up of PCBs in the body of one organism over its lifetime?
[1 mark]
ABioaccumulation
BBiomagnification
CEutrophication
DBiodegradation
(b)
What is meant by biomagnification of PCBs in this food chain?
[1 mark]
APCBs break down faster at higher trophic levels
BPCBs move from land to the sea
CThe concentration of PCBs increases at each successive trophic level
DThe concentration of PCBs decreases along the food chain
(c)
Explain why the orcas have much higher concentrations of PCBs than the zooplankton.
[2 marks]
Total for question 6: 4 marks
7
Isle Royale is an island national park in Lake Superior, North America. Moose reached the island about a century ago, and wolves crossed the winter ice in about 1949. The moose population has risen and fallen over time. It fell after harsh winters and an outbreak of ticks, and it grew when wolf numbers were low. By 2016 only two wolves remained, because inbreeding reduced the survival of pups, and wolves from the mainland were introduced from 2018.
(a)
Explain how density-dependent factors and negative feedback can regulate the size of the moose population.
[3 marks]
(b)
Discuss whether the concept of carrying capacity can easily be applied to human populations.
[4 marks]
Total for question 7: 7 marks
8
In 1883 the eruption of Krakatau in Indonesia destroyed most of the island and covered what remained in hot ash, killing all life. Cyanobacteria and mosses were among the first colonists, followed by grasses and ferns, then shrubs and trees. Within about 50 years forest had returned, and the island now supports many species. In parts of Mediterranean Spain, by contrast, centuries of goat grazing and burning have kept some land as open scrub, although the climate would support oak woodland.
(a)
Describe and explain how the community and the abiotic environment changed during primary succession on Krakatau.
[6 marks]
(b)
Discuss the roles of r- and K-strategist species in succession and the evidence that the idea of a climax community is uncertain.
[6 marks]
Total for question 8: 12 marks

End of questions

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).