20) Human influences on ecosystems (3.4)

Question 1

1.1.1. Describe how humans have increased food production, limited to agricultural machinery to use larger areas of land and improve efficiency

Answer 1

Agricultural machinery has replaced humans and improved efficiency due to the ability to farm much larger areas of land

Tractors and ploughs prepare land for sowing seeds

Combine harvesters harvest crops

Soil monitoring sensors monitor the soil

Drones monitor fields

Question 2

1.1.2. Describe how humans have increased food production, limited to chemical fertilisers to improve yields

Answer 2

Chemical fertilisers encourage the growth of crop plants, increasing the yield of the crop.

Fertilisers increase the amount of nutrients in the soil

This lets them grow larger and produce more fruit

Question 3

1.1.3. Describe how humans have increased food production, limited to insecticides to improve quality and yield

Answer 3

Pesticides kill pests like insects

Less damage is done to the plants and less fruit is lost to insects

Question 4

1.1.4. Describe how humans have increased food production, limited to herbicides to reduce competition with weeds

Answer 4

Herbicides kill weeds that compete with crop plants for water, light and nutrients

Question 5

1.1.5. Describe how humans have increased food production, limited to selective breeding to improve production by crop plants and livestock

Answer 5

Selective breeding increases yield and makes crops more resistant to drought + diseases

Animals and crop plants which produce a large yield are selectively bred

This produces breeds that reliably produce high yields

Question 6

1.2.0. What is monoculture farming?

Answer 6

When only one type of crop is grown on a given area of agricultural land, which does not occur naturally in ecosystems

Usually there are many different species of plants which support many species of animals (high biodiversity)

Question 7

1.2.1. Describe the advantages of large-scale monocultures of crop plants

Answer 7

Increased machinery means continuous cropping

Decrease in labour costs

Only one crop is grown so it can be selectively bred to increase yield

Selective use of fertilisers and pesticides increases yield

Soil pH can be regulated

Question 8

1.2.2. Describe the disadvantages of large-scale monocultures of crop plants

Answer 8

Destroying areas of natural vegetation between fields reduces biodiversity of plants and animals

Excess fertilisers can leach into rivers causing eutrophication killing fish and invertebrates

Pesticides may enter the food chain

Unlike organic fertilisers, chemical fertiliser do not improve soil structure

If a particular pest feeds on a crop, farming it in large areas gives it an ample supply of food, causing the population to rise

Harmless insects might be killed due to insecticide

Pests may eventually become resistant if insecticide is used repeatedly

Question 9

1.3.0. What is intensive livestock production?

Answer 9

Using modern technology to achieve high yields of crop plants and livestock

Crops are grown over large areas at high densities

Livestock is kept in large numbers, their food supply is supplemented and their movement is often restricted by being kept indoors

Question 10

1.3.1. Describe the advantages of intensive livestock production

Answer 10

Animals reared indoors can be given high-protein diets and additives so they grow as fast as possible

Temperature of housing is kept constant since animals grow well in warmth

Antibiotics can be used to control disease

Keeping animals in cages or pens restricts their exercise so they put on weight faster

Question 11

1.3.2. Describe the disadvantages of intensive livestock production

Answer 11

Many people think it is more humane for them to be outside

Being caged in overcrowded conditions causes obesity, boredom and frustration

Rearing animals in crowded conditions can lead to a rapid spread of disease

Fish farming can cause pollution, as many fish in one place means animal waste and uneaten food can cause eutrophication

Animals, especially cattle, generate lots of methane, which is a greenhouse gas

Question 12

2.1. Describe biodiversity

Answer 12

The number of different species that live in an area

Question 13

2.2.1. Describe why increased area for housing, crop plant production and livestock production has caused habitat destruction

Answer 13

The increasing human population means that there is a higher demand for food

Crops, livestock and housing take up a large amount of space

The amount of land available for these things must be increased by clearing habitats such as forests (deforestation)

Question 14

2.2.2. Describe why extraction of natural resources has caused habitat destruction

Answer 14

Natural resources such as wood, stone and metals must be gathered to make products

Many trees are cut down, destroying forest habitats

Some resource extraction also takes up lots of space (e.g. mining, as land must be cleared for it first)

Question 15

2.2.3. Describe why extraction of natural resources has caused freshwater and marine pollution

Answer 15

Oil spills and other waste pollutes the oceans, killing marine life

Eutrophication occurs due to fertilisers from intensively farmed fields entering waterways

Most aquatic species living in these waterways die from lack of oxygen, causing a huge decrease in biodiversity

Question 16

2.3. How can humans have a negative impact on habitats?

Answer 16

Through altering food webs and food chains

Question 17

2.4. Explain the undesirable effects of deforestation as an example of habitat destruction, to include: reducing biodiversity, extinction, loss of soil, flooding and increase of carbon dioxide in the atmosphere

Answer 17

Extinction/loss of biodiversity: forest habitats, especially tropical rainforests, have a huge range of biodiversity and its destruction causes the loss of large numbers of plant and animal species. Many species are only found in these areas and become extinct

Soil erosion: tree roots stabilise soil, preventing it from being eroded by rain, and usually take up nutrients and minerals from soil. Without trees, they remain unused and they will be washed away by rain (leaching), which is permanent and makes it difficult for trees to regrow

Flooding: the topsoil will be loose so it will be easily washed away by rain, increasing the risk of flash flooding and landslides

Increase of carbon dioxide in the atmosphere: less carbon dioxide is being removed from the atmosphere and less oxygen is released. Trees are also often burned, which releases carbon dioxide (an example of combustion)

Question 18

3.1. Describe the effects of untreated sewage and excess fertiliser on aquatic ecosystems (note use point 4 for to explain details of the eutrophication process)

Answer 18

Untreated sewage and the deaths of algae from algae blooms caused by excess fertiliser provides a good source of food for bacteria

Bacteria depletes oxygen dissolved in water as they respire aerobically, causing aquatic organisms such as fish to die (eutrophication)

Question 19

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

Answer 19

Marine animals try to eat plastic or get caught in it, leading to injuries and deaths

Plastic releases toxins as it breaks down, which may affect marine organisms

Tiny plastic particles enter the food chain through animals consuming them

Plastic in landfills release toxins into the surrounding soil, so the land becomes bad for growing crops or grazing animals and can only be used for building on decades after burial

Question 20

3.4. Explain the process of eutrophication of water

Question 21

4.1. Describe a sustainable resource

Answer 21

A resource that is produced as rapidly as it is removed from the environment so that it does not run out

Question 22

4.2. What are some resources that can be conserved and managed sustainably?

Answer 22

Forests and fish stocks

Question 23

4.2. What are some resources that can be conserved and managed sustainably?

Answer 23

Forests and fish stocks

Question 24

4.3. Explain why organisms become endangered or extinct, including: climate change, habitat destruction, hunting, overharvesting, pollution and introduced species

Answer 24

Climate change: forces species to adapt to new climate patterns, so many species must migrate to new areas that meet their needs. Species that cannot adapt quickly enough die, leading to extinction (e.g. loss of ice from the Arctic reduces hunting sites for polar bears)

Habitat destruction: more land is being used for agriculture, including previously unusable land that has been drained. The carrying capacity for indigenous plants, animals, and other organisms is reduced, so populations decline, removing habitats for many species, such as wading birds and amphibians

Hunting: pests have been hunted ruthlessly, such as the red deer (which damages trees), predators such as cheetahs, and scavengers such as vultures

Overharvesting: reduces valuable living resources to such low levels that their exploitation is no longer sustainable

Pollution: ponds and rivers may be polluted by fertilisers and sewage, so many oxygen-requiring species can be lost

Introduced species: predators such as stoats and weasels introduced to offshore islands can eliminate ground-nesting birds

Question 25

4.4.1. Describe how endangered species can be conserved through monitoring and protecting species and habitats

Answer 25

Monitoring and protecting species will ensure that they have the best conditions to survive

Problems can be removed before they cause too much harm

Question 26

4.4.2. Describe how endangered species can be conserved through education

Answer 26

The more people aware of the importance of conservation, the more will be inclined to do something about it

More people will know what species face endangerment, so they’ll be better protected

Question 27

4.4.3. Describe how endangered species can be conserved through captive breeding programmes

Answer 27

Ensures the population will rise again, and eventually the species can return to the wild

Question 28

4.4.4. Describe how endangered species can be conserved through seed banks

Answer 28

Seeds of endangered plant species are carefully stored so that new plants may be grown in the future, ensuring the population will eventually rise again

Question 29

4.5. Explain how forests can be conserved using: education, protected areas, quotas and replanting

Answer 29

Forests are needed to produce paper products and provide wood for timber

Much of the world’s paper is now produced from forests which replant similar trees when mature trees are cut, ensuring that there will be adequate supply in the future

Tropical hardwoods such as teak and mahogany take many years to regrow but are highly desirable for furniture

Using these types is more sustainable due to the introduction of several schemes designed to monitor logging companies and track the wood produced

Education ensures logging companies are aware of sustainable practices and consumers know the importance of buying products made from sustainable sources

Question 30

4.6. Explain how fish stocks can be conserved

Answer 30

Educating fishermen as to local and international laws, and educating consumers as to types of fish not produced sustainably and to buying avoid them

Controlling the time of year certain fish can be caught (to prevent large scale depletion when fish come together in large numbers in certain areas to breed)

Controlling the number of fish caught each year

Controlling the size of fish caught (ensures there are enough fish of suitable age for breeding remaining)

Restocking (breeding and keeping offspring until they are large enough to survive in their natural habitat then releasing)

Question 31

4.7. Describe the reasons for conservation programmes

Answer 31

Maintaining or increasing biodiversity: allows ecosystems to remain stable

Reducing extinction: retains iconic species and maintain biodiversity

Protecting vulnerable ecosystems: they would be lost to human activity without intervention

Maintaining ecosystem functions: nutrient cycling eg. carbon cycling to hold back climate change. Resource provision, such as making sure we have enough food for the population, having access to plants for plant-based remedies, fuel for important activities such as cooking and genes so the gene pool remains wide and variety exists in all species

Question 32

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

Answer 32

Certain conservation techniques can be used to maintain biodiversity

Artificial insemination (AI): allows large numbers of offspring to be produced without the need for conventional sexual intercourse

In vitro fertilisation (IVF): allows gametes with known alleles to be used in ensuring the next generation remains biodiverse

Question 33

4.9. Explain the risks to a species if its population size decreases, reducing genetic variation (knowledge of genetic drift is not required)

Answer 33

Reduced genetic variation makes a species more susceptible to environmental change, increasing the risk of extinction