Chapter 20: Human Influence

Question 1

Describe how humans have increased food production

Answer 1

(a) agricultural machinery to use larger areas of land and improve efficiency
(b) chemical fertilisers to improve yields
(c) insecticides to improve quality and yield
(d) herbicides to reduce competition with weeds
(e) selective breeding to improve production by crop plants and livestock

Question 2

Describe the advantages and disadvantages of large-scale monocultures of crop plants

Answer 2

Advantages: It makes farming much more efficient, keeps down costs. Machines and procedures can be used totally systematically on a large scale.
Disadvantages: It totally removes all of the diversity of the natural land and eliminates the habitat of almost all of the other plants and animals that lived there before the monoculture.

Question 3

Describe the advantages and disadvantages of intensive livestock production

Answer 3

Adv
High Output
more efficient in resource usage
Cost-Effectiveness
Disadv
Habitat Destruction
Reduced Genetic Diversity
Greenhouse Gas Emissions

Question 4

Describe biodiversity

Answer 4

the number of different species that live in an area

Question 5

Describe the reasons for habitat destruction

Answer 5

(a) increased area for housing, crop plant production and livestock production
(b) extraction of natural resources
(c) freshwater and marine pollution

Question 6

How humans can have a negative impact on habitats

Answer 6

altering food webs and food chains

Question 7

undesirable effects of deforestation

Answer 7

reducing biodiversity, extinction, loss of soil, flooding and increase of carbon dioxide in the atmosphere

Question 8

State the effects of untreated sewage on water pollution

Answer 8

Sewage contains nitrates. Nitrates are used by algae to make proteins for growth. Excess nitrates can cause algal blooms and eutrophication.

Question 9

State the effects of fertiliser use on water pollution.

Answer 9

Fertilisers contain nitrates.
Excess fertilisers are washed into bodies of water by the rain.
Nitrates are used by algae to make proteins for growth, which leads to algal blooms and eutrophication.

Question 10

Explain the process of eutrophication of water

Answer 10

• increased availability of nitrate and other ions
• increased growth of producers
• increased decomposition after death of
producers
• increased aerobic respiration by decomposers
• reduction in dissolved oxygen
• death of organisms requiring dissolved oxygen in water

Question 11

Describe the effects of non-biodegradable plastics, in both aquatic and terrestrial ecosystems

Answer 11

Pollute soli and water

Question 12

Describe the sources and effects of pollution of the air by methane and carbon dioxide, limited to: the enhanced greenhouse effect and climate change

Answer 12

When excess carbon dioxide and methane are released in the air it can cause climate change and worsens the greenhouse effect. These substances speed up the rate of climate change because they absorb infrared radiation.

Question 13

Describe a sustainable resource

Answer 13

one which is produced as rapidly as it is removed from the environment so that it does not run out

Question 14

Explain how forests can be conserved using:

Answer 14

education, protected areas, quotas and replanting

Question 15

Explain how fish stocks can be conserved using:

Answer 15

education, closed seasons, protected areas, controlled net types and mesh size, quotas and monitoring

Question 16

Explain why organisms become endangered or extinct, including:

Answer 16

climate change, habitat destruction, hunting, overharvesting, pollution and competition from introduced species

Question 17

Describe how endangered species can be conserved

Answer 17

(a) monitoring and protecting species and habitats
(b) education
(c) captive breeding programmes (breeding of endangered animals in enclosures (such as zoos) to increase population numbers and preserve biodiversity.)
(d) seed banks (seeds of endangered plant species are carefully stored so that new plants may be grown in the future.)

Question 18

Describe the reasons for conservation programmes

Answer 18

(a) maintaining or increasing biodiversity
(b) reducing extinction
(c) protecting vulnerable ecosystems
(d) maintaining ecosystem functions, limited to nutrient cycling and resource provision, including food, drugs, fuel and genes

Question 19

Describe the use of artificial insemination (AI) and in vitro fertilisation (IVF) in captive breeding programmes

Answer 19

AI-artificially introducing sperm into a female’s reproductive tract to fertilise her eggs. Adv male infertile or the don’t for bonds
IVF- allowing fertilisation of an egg with sperm outside the body in a controlled lab setting.

Question 20

Explain the risks to a species if its population size decreases, reducing genetic variation

Answer 20

a population cannot adapt/ susceptible to changing environmental variables and, as a result, may face an increased risk of extinction.