Human Influences on EcosystemsCambridge IGCSE Biology: Topic test

20 questions, 54 marks

Cambridge IGCSE Biology

Human Influences on Ecosystems topic test

Total 54 marks

Name

Class

Date

1
A commercial strawberry grower increases food production using a heated glasshouse that keeps light, temperature and carbon dioxide concentration at levels which maximise the rate of photosynthesis, together with a drip-irrigation system that delivers a nutrient-rich fertiliser solution directly to each plant's roots.
(a)
Which of the following best explains why supplying extra carbon dioxide inside the glasshouse increases strawberry yield?
[1 mark]
ACarbon dioxide is a raw material for photosynthesis, so increasing its concentration can increase the rate of photosynthesis and therefore growth
BCarbon dioxide directly provides the plant with nitrate ions needed for growth
CCarbon dioxide kills insect pests that would otherwise eat the strawberry plants
DCarbon dioxide replaces the need for water in the glasshouse
(b)
What is the main purpose of applying a nutrient-rich fertiliser solution to the strawberry plants' roots?
[1 mark]
ATo directly increase the rate of photosynthesis inside the leaf cells
BTo supply mineral ions, such as nitrate, that the plant needs to make substances such as amino acids and proteins for healthy growth
CTo kill fungal diseases affecting the strawberry plants
DTo increase the concentration of carbon dioxide available to the plant
(c)
Explain one advantage of growing strawberries in a controlled glasshouse environment like this, compared with growing them outdoors without any such controls, in terms of food production.
[2 marks]
Total for question 1: 4 marks
2
A tourism company reclaims land along a tropical coastline to build a new resort, filling in a large area of shallow coastal water with sand and rock. This construction work buries and destroys a large area of coral reef habitat that was previously home to many species of fish and other marine organisms.
(a)
Which of the following is the best definition of biodiversity?
[1 mark]
AThe total mass of living organisms in a particular area
BThe number of individual organisms of a single species living in an area
CThe number of different species living in an area
DThe number of trophic levels present in a food chain
(b)
What is the most likely immediate effect of destroying this area of coral reef habitat on the local marine biodiversity?
[1 mark]
ABiodiversity would increase, because more space becomes available for new species
BBiodiversity would be completely unaffected, since fish can simply swim to a different reef
CBiodiversity would only be affected if the resort construction also released pollution
DBiodiversity would decrease, as species that depended on the reef habitat lose their home and food sources
(c)
Explain why the loss of this area of coral reef habitat could lead to some marine species becoming endangered or extinct in the region.
[2 marks]
Total for question 2: 4 marks
3
An oil tanker runs aground off a coastline, spilling a large quantity of crude oil into the surrounding sea. Within days, a thick layer of oil covers a wide area of the sea's surface and begins washing up on nearby beaches, coating rocks, sand and the feathers of seabirds.
(a)
Describe three ways in which the oil spill could directly harm seabirds living along this coastline.
[3 marks]
(b)
Explain how the oil spill could affect the wider marine food chain in this area, beyond the direct effects on seabirds.
[4 marks]
Total for question 3: 7 marks
4
A species of freshwater river dolphin, found only in one large river system, has become critically endangered. Its decline has been caused by a combination of dam construction that fragments its habitat into isolated stretches of river, and toxic chemical pollution released into the river from nearby factories. Conservationists are now developing a programme to try to save the remaining population.
(a)
Explain how each of the two factors described above, dam construction and chemical pollution, has contributed to the decline of the river dolphin population, and explain why a species restricted to a single river system, like this dolphin, is especially vulnerable to habitat destruction.
[6 marks]
(b)
Suggest and explain two different conservation methods that could be used to help protect and increase the numbers of this critically endangered river dolphin population.
[6 marks]
Total for question 4: 12 marks
5
A poultry farm increases meat production by rearing broiler chickens that have been selectively bred over many generations to grow much faster and larger than their wild ancestors. The chickens are kept indoors at a high stocking density, in buildings where temperature and lighting are carefully controlled.
(a)
Which method has been used to produce broiler chickens that grow faster and larger than their wild ancestors?
[1 mark]
AGenetic modification
BNatural selection
CSelective breeding
DPasteurisation
(b)
What is the main reason for keeping the chickens' housing at a carefully controlled temperature?
[1 mark]
ATo increase the amount of oxygen available to the chickens
BTo increase the rate of photosynthesis in the chickens
CTo prevent the chickens from being selectively bred further
DTo reduce the energy the chickens need to use to keep warm, so more energy from their food can be used for growth
(c)
Explain one disadvantage of rearing broiler chickens at a high stocking density indoors, in terms of animal welfare or disease.
[2 marks]
Total for question 5: 4 marks
6
A large landfill site, where household waste is buried, produces significant amounts of methane gas as the buried organic waste decomposes without oxygen. Much of this methane escapes into the atmosphere from the landfill site.
(a)
What effect does the release of methane from the landfill site into the atmosphere have on global climate?
[1 mark]
AIt contributes to the enhanced greenhouse effect and climate change
BIt has no effect on global climate
CIt directly destroys the ozone layer
DIt reduces the concentration of oxygen in the atmosphere
(b)
Why does the buried waste in the landfill site produce methane rather than carbon dioxide as it decomposes?
[1 mark]
ABecause the waste is decomposing in the presence of large amounts of oxygen
BBecause the waste is decomposing without the presence of oxygen
CBecause the waste has been treated with fertiliser
DBecause the waste contains only inorganic (non-living) material
(c)
Explain why methane released from the landfill site contributes to global warming.
[2 marks]
Total for question 6: 4 marks
7
A species of butterfly, found only on a small number of chalk grassland hillsides in one country, has declined sharply in number as much of its grassland habitat has been lost to new building development. Conservationists want to prevent this butterfly species from becoming extinct.
(a)
Describe three conservation methods that could be used to help protect this declining butterfly species.
[3 marks]
(b)
The butterfly's caterpillars feed only on one particular species of wild flower that grows on chalk grassland. Explain why this makes the butterfly particularly vulnerable to extinction, and suggest one further conservation action, related to this food plant, that could help protect the butterfly.
[4 marks]
Total for question 7: 7 marks
8
A coastal salmon farming company keeps thousands of salmon in large cages in the sea to increase fish production for food. The farmed salmon are fed a high-protein pellet feed, and uneaten feed along with the fish's waste falls through the cages into the surrounding water below.
(a)
Explain how this method of fish farming can increase food production compared with catching wild fish, and explain how the uneaten feed and waste falling from the cages could lead to eutrophication of the surrounding coastal water.
[6 marks]
(b)
Suggest and explain two ways that the salmon farming company, or local conservation authorities, could reduce the environmental impact of this fish farm on the surrounding marine ecosystem, while still allowing fish production to continue.
[6 marks]
Total for question 8: 12 marks

End of questions