Effects of humans on ecosystems
19.4What the syllabus asks of you
- Outline the causes and describe the consequences of deforestation, limited to its effects on: biodiversity, extinction, loss of soil, flooding and concentration of carbon dioxide in the atmosphere
- Describe the impacts humans have through: (a) over-harvesting of plant and animal species (b) introducing a non-native species to an ecosystem
- Describe the harmful effects of: (a) water pollution by untreated sewage and nitrogen-containing fertilisers leading to eutrophication, limited to: (i) increased availability of nitrate and other ions (ii) increased growth of producers (iii) increased decomposition after death of producers (iv) increased aerobic respiration by decomposers (v) reduction in dissolved oxygen (vi) death of organisms requiring dissolved oxygen in water (b) air pollution by greenhouse gases (carbon dioxide and methane), contributing to global warming and its likely effects (c) pollution due to insecticides and herbicides (d) non-biodegradable plastics in the environment, in both aquatic and terrestrial ecosystems
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Chapter 19: Effects of humans on ecosystems
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8 questions
1Oct / Nov 2020 · Paper 11 · Q32Show mark scheme →
AIt becomes more concentrated at each stage in the food web.
BIt breaks down within a few months.
CIt destroys one particular insect only.
DIt destroys the immature forms of an insect.
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2Oct / Nov 2020 · Paper 12 · Q32Show mark scheme →
AIt becomes more concentrated at each stage in the food web.
BIt breaks down within a few months.
CIt destroys one particular insect only.
DIt destroys the immature forms of an insect.
Mark scheme
3May / June 2020 · Paper 11 · Q32Show mark scheme →
Aatmospheric carbon dioxide: decreases; number and variety of species: decreases; soil stability: increases
Batmospheric carbon dioxide: decreases; number and variety of species: increases; soil stability: decreases
Catmospheric carbon dioxide: increases; number and variety of species: decreases; soil stability: decreases
Datmospheric carbon dioxide: increases; number and variety of species: decreases; soil stability: increases
Mark scheme
4May / June 2020 · Paper 12 · Q32Show mark scheme →
Ainsecticides: yes | methane: yes | fertiliser: yes | sulfur dioxide: no
Binsecticides: yes | methane: yes | fertiliser: no | sulfur dioxide: yes
Cinsecticides: yes | methane: no | fertiliser: yes | sulfur dioxide: yes
Dinsecticides: no | methane: yes | fertiliser: yes | sulfur dioxide: yes
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5Oct / Nov 2019 · Paper 11 · Q32Show mark scheme →
AA
BB
CC
DD
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6Oct / Nov 2019 · Paper 12 · Q32Show mark scheme →
Acarbon dioxide
Binsecticides
Cmethane
Dnitrogen-containing chemicals
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7May / June 2019 · Paper 11 · Q32Show mark scheme →
Aholding silt in the reservoir so that it is not spread on the flood plain
Bproviding a reservoir of still water for mosquito larvae
Cseparating migrating fish from spawning grounds
Dstoring water for humans to drink
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8May / June 2019 · Paper 12 · Q32Show mark scheme →
A1 and 2
B2 and 3
C3 and 4
D4 and 1
Mark scheme