Biology: 3.6 Human impact on the environment

Question 1

What natural occurrences can cause natural selection?

Answer 1

Climatic changes, geological changes, biotic changes and natural disasters.

Question 2

What causes the decline in numbers of large mammals?

Answer 2

Loss of habitat - deforestation, loss of hedgerows and drainage of wetlands to provide more land for food production.
Over hunting - including overfishing, removal of species to reduce competition monocultures.
Competition - from species introduced as food
Pollution - leading to bioaccumulation eg, oil spills, increased CO2 emissions leading to climate change.

Question 3

What is species conservation?

Answer 3

The sensible management of the biosphere and enhancement of biodiversity locally. Examples include habitat protection by nature reserves and SSSI.

Question 4

What does the conservation of species ensure?

Answer 4

1: Conservation of existing gene pools in the wild and in captivity.
2: It prevents the loss of potentially useful genes to man.
3: It maintains the genetic diversity of the species.

Question 5

How does breeding help with preventing the loss of species?

Answer 5

Breeding increases genetic uniformity with the loss of rarer alleles.

Question 6

What is a gene pool?

Answer 6

The total number of genes of every individual in an interbreeding population.

Question 7

What does a large gene pool indicate?

Answer 7

High genetic diversity,increased chances of biological fitness and survival.

Question 8

What does a small gene pool indicate?

Answer 8

Low genetic diversity, reduced chances of acquiring biological fitness and increased possibility of extinction.

Question 9

How does a gene pool increase?

Answer 9

When mutation occurs and survives.

Question 10

How does a gene pool decrease?

Answer 10

When the population size is significantly reduced e.g. famine, genetic disease etc.

Question 11

What are the consequences of a small gene pool?

Answer 11

Low fertility, and increased probability of acquiring diseases and deformities.

Question 12

What has greater use of fertilisers led to?

Answer 12

1: Increase mineral content of soil enabling increased plant growth.
2: Reduce competition from weeds
3: Reduce amount of crops eaten by pests.

Question 13

What has increased mechanisation led to?

Answer 13

Increases speed and efficiency of soil preparation, planting and harvesting.

Question 14

What has increased size of fields led to?

Answer 14

Enables use of larger machinery.

Question 15

Why are hedges removed from agricultural land?

Answer 15

1: They take up space.
2: Easier access is needed for large machinery.
3: They harbour pests, diseases and weeds

Question 16

Why do hedges have conservation value?

Answer 16

1: They prevent soil erosion by the wind.
2: Provide a habitat for plants and animals.
3: Provide food for animals which may not live in the hedgerows.

Question 17

How is management of farms to ensure sustainability and to reduce the impact on wildlife achieved?

Answer 17

1: Control use of pesticide.
2: The maintenance of habitat variety.
3: The prevention of erosion.

Question 18

How is climate change a consequence of deforestation?

Answer 18

Tropical rain forests remove a large amount of carbon dioxide from the atmosphere each year.

Question 19

How is destruction of natural habitat a consequence of deforestation?

Answer 19

This leads to a reduction in biodiversity and the loss of many species of plants and animals.

Question 20

How is soil erosion a consequence of deforestation?

Answer 20

The loss of trees allows more water to penetrate to the earth and the lack of roots means that during heavy rain soil can be washed away.

Question 21

What is slash and burn?

Answer 21

It is an agriculture and forestry practice that clear large areas of forest before replanting and is largely the cause of habitat destruction and loss of biodiversity.

Question 22

What is coppicing?

Answer 22

Doesn’t completely remove trees but removes the larger shoots allowing regeneration of new shoots from the base of the trees.

Question 23

What is selective cutting?

Answer 23

Removes larger trees allowing more light into the forest and therefore increased growth of remaining trees.

Question 24

How is long rotation times a forest management technique?

Answer 24

Long rotation times allows trees to grow for many years before harvesting them. This allows for the forest to develop greater biodiversity, nutrient levels in the soil to increase and a greater yield from the trees when they are harvested.

Question 25

What is afforestation?

Answer 25

Afforestation requires the replanting of trees, ideally at the same rate that trees are removed - this maintains forest ecosystems and habitats even though trees are being felled.

Question 26

What is ecotourism?

Answer 26

It involves the setting up of protected areas where logging and tree clearance is not allowed but tourists pay to observe plants and animals in their natural habitats.

Question 27

What are the effects of overfishing on other wildlife?

Answer 27

Drift nets and trawlers are indiscriminate as they catch any animals that happen to be in the way.

Question 28

What are some solutions to overfishing?

Answer 28

1: Imposing quotas to limit the size of catches.
2: Restricting mesh size of nets.
3: Enforcing closed seasons to prevent fishing during breeding seasons.
4: Enforcing exclusion zones to prevent fishing in breeding areas or nursery grounds.

Question 29

What are some problems with fish farming?

Answer 29

1: Intensive fish farming leads to large numbers of fish being kept in small volumes of water.
2: Disease and parasites can spread rapidly which can then spread to wild fish.
3: Eutrophication can result from the use of fertilisers and from large amounts of fish excreta and waste food being released into the water.