Chapter 20 - Human influences on ecosystems

Question 1

Why has agricultural machinery replace humans?

Answer 1

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

Question 2

Why are chemical fertilisers used in agriculture?

Answer 2

Chemical fertilisers to improve yields as fertilisers increase the amount of nutrients in the soil for plants, meaning that they can grow larger and produce more fruit.

Question 3

Why are insecticides and herbicides used in agriculture?

Answer 3

Insecticides and herbicides as these chemical kill off unwanted insects and weed species meaning that there is less damage done to plants and fruits lost to insects as well as reducing competition from other species.

Question 4

Why is selective breeding used in agriculture?

Answer 4

Selective breeding is when animals and crop plants which produce a large yield are selectively bred to produce breeds that reliably produce high yields.

Question 5

Why are monocultures used in agriculture?

Answer 5

Monocultures are when only one type of crop is grown on a given area of land. This increases crop yield, can be managed more efficiently with agricultural machinery and it is more profitable, and crops has little competition. However, it lowers biodiversity, increases pest populations and the overuse of insecticides could lead to harmless insects being killed, pollution or resistance.

Question 6

Why is intensive livestock farming used in agriculture?

Answer 6

Intensive livestock farming require less land to produce large amounts of food, food can be produced all year round in controlled environments, the cost of production is lower and there is a lower requirement for labour. However, the use of herbicides could result in eutrophication, pesticides could cause negative effects on the food chain, ethical issues arise due to the cruel treatment of animals, natural habitats may be destroyed, reduction in biodiversity, overgrazing can lead to soil erosion and large numbers of cattle produce large amounts of methane which is a greenhouse gas.

Question 7

What is biodiversity?

Answer 7

Biodiversity is the number of different species that live in an area.

Question 8

What are three causes of habitat destruction?

Answer 8

Increased area for housing, crop plant production and livestock production, extraction of natural resources and marine pollution?

Question 9

How does increased area for housing, crop plant production and livestock production lead to habitat destruction?

Answer 9

Increased area for housing, crop plant production and livestock production as they all take up a large amount of space and as there is an increasing world population and the demand for food, the amount of land available for these things must be increased by clearing habitats such as forests.

Question 10

How does extraction of natural resources lead to habitat destruction?

Answer 10

Extraction of natural resources as resources such as wood, stone and metals must be gathered to make different products. Therefore, many trees are cut down, destroying forest habitats. In addition, some resource extraction takes up a large amount of space.

Question 11

How does marine pollution lead to habitat destruction?

Answer 11

Marine pollution as human activities lead to the pollution of marine habitats. In many places, oil spills and other waste pollutes the oceans, killing sea life. Also, eutrophication can occur when fertilisers from intensively farmed fields enters waterways. This causes a huge decrease in biodiversity in these areas as most aquatic species living in these waterways die from a lack of oxygen.

Question 12

How can humans negatively impact habitats?

Answer 12

Through the altering food webs and food chains, human can have a negative impact on habitats.

Question 13

What are four undesirable effects of deforestation?

Answer 13

Extinction/loss of biodiversity, soil erosion, flooding and increased carbon dioxide in atmosphere

Question 14

What is the consequence of extinction/loss of biodiversity?

Answer 14

Forest habitats, especially tropical rainforests, have a huge rage of biodiversity and as habitats are destroyed it cause the loss of large numbers of plant and animal species. Many of these species are only found in these areas and therefore will become extinct.

Question 15

What is the consequence of soil erosion?

Answer 15

Tree roots help to stabilise the soil, preventing it from being eroded by rain. Trees usually take up nutrients and minerals from the soil through their roots. Without trees, nutrients and minerals will remain unused in the soil so will be washed away into rivers and lakes by rain (leaching). The loss of soil nutrients is permanent and makes it very difficult for forest trees to regrow, even if the land is not cultivated with crop plants or grass for cattle.

Question 16

What is the consequence of flooding?

Answer 16

Without trees the topsoil will be loose and unstable so will be easily washed away by rain, increasing the risk of flash flooding and landslides.

Question 17

What is the consequence of increase carbon dioxide in the atmosphere?

Answer 17

Trees carry out photosynthesis during which they take in carbon dioxide and release oxygen. The removal of significant numbers of trees means less carbon dioxide is being removed from the atmosphere and less oxygen released. When areas of land in forests are cleared for land use, the trees are often burned as opposed to being cut down, this releases carbon dioxide (combustion) further increasing carbon dioxide levels in the atmosphere and contributing to global warming.

Question 18

What is the source/cause of untreated sewage?

Answer 18

Lack of sewage treatment plants in inhibited areas due to poor infrastructure or a lack of money means that sewage runs into streams or rivers.

Question 19

What is the effect of untreated sewage?

Answer 19

Provides a good source of food for bacteria which increase rapidly depleting the oxygen dissolved in the water as they respire aerobically and causing the death of aquatic organisms such as fish this is known as eutrophication.

Question 20

What is the source/cause of chemical waste?

Answer 20

Chemicals such as heavy metals like mercury can be released from factories into rivers and oceans or leach into land surrounding the factories.

Question 21

What is the effect of chemical waste?

Answer 21

Many heavy metals and other chemicals are persistent meaning they do not break down and so can build up in food chains, known as bioaccumulation, poisoning the top carnivores.

Question 22

What is the source/cause of discarded rubbish?

Answer 22

Much rubbish consists of plastic that is either discarded or buried in landfills.

Question 23

What is the effect of discarded rubbish?

Answer 23

Much rubbish that is made from plastic is non-biodegradable and remains in the environment for hundreds of years. Animals also eat the plastic as it breaks into spaller pieces, and it can get into food chains this way.

Question 24

What is the source/cause of fertilisers?

Answer 24

Runoff from agricultural land is applied in too high of a concentration

Question 25

What is the effect of fertilisers?

Answer 25

Causes algae blooms which then die and provide a good source of food for decomposing bacteria which increase rapidly, depleting the oxygen dissolved in the water as they respire aerobically and causing the death of aquatic organisms such as fish. This is known as eutrophication.

Question 26

What is the source/cause of insecticides and herbicides?

Answer 26

Sprayed on crops to prevent damage by insects and growth of weeds.

Question 27

What if the effect of insecticides and herbicides?

Answer 27

Bioaccumulation, loss of biodiversity, damage to beneficial insects, build up in soil to toxic concentrations and harm other organisms.

Question 28

What is the source/cause of nuclear fallout?

Answer 28

Radioactive particles that get into the environment from accidental leakage from nuclear power plants or an explosion of a nuclear bomb.

Question 29

What is the effect of nuclear fallout?

Answer 29

Some radioactive particles have long half lives and can remain in the environment for many years. They can cause increased risks of cancer and smaller particles can be carried by winds hundred of miles from the original site of exposure.

Question 30

What is the source/cause of methane?

Answer 30

Cattle farming, rice fields and landfills.

Question 31

What is the effect of methane?

Answer 31

Methane is a greenhouse gas which contributes to the enhanced greenhouse effect that is causing climate change.

Question 32

What is the source/cause of carbon dioxide?

Answer 32

Produced when fossil fuels are burnt, also released when trees are burnt to clean land for human use.

Question 33

What is the effect of carbon dioxide?

Answer 33

Carbon dioxide is a greenhouse gas which contributes to the enhanced greenhouse effect that is causing climate change.

Question 34

What is eutrophication?

Answer 34

Eutrophication is caused when run off of fertiliser enters the water way and due to the increased availability of nitrate and other ions, it leads to the increased growth of producers, algae. This algae bloom blocks sunlight so water plants on the bottom start to die. This leads to the decomposition of these dead plants using aerobic respiration which leads to a reduction is dissolved oxygen. Therefore, the organisms that require oxygen would die.

Question 35

What is a sustainable resource?

Answer 35

Sustainable resources are ones which are produced as rapidly as it is removed from the environment so that it does not run out.

Question 36

How can forests be conserved?

Answer 36

Forests can be conserved using education, protected areas, quotas, and replanting.

Question 37

How can fish stocks be conserved?

Answer 37

Fish stocks can be conserved by using education, closed seasons, protected areas, controlled net types and mesh size, quotas, and monitoring.

Question 38

Why may the population of a species fall?

Answer 38

An endangered species is at risk of becoming extinct. The population of the species may fall due to hunting, climate change, pollution, loss of habitat or the introduction of a non-native species.

Question 39

How can endangered species be conserved?

Answer 39

Endangered species can be conserved by monitoring and protecting species and habitats, education, captive breeding programmes and seed banks.

Question 40

What do conservation programmes do?

Answer 40

Conservation programmes help to maintain or increase biodiversity, reduce extinction, protecting vulnerable ecosystems and maintaining ecosystem’s function (limited to nutrient cycling and resource provision including goods, drugs, fuel, and genes.)

Question 41

What is artificial insemination (AI)?

Answer 41

Artificial insemination (AI) allows large numbers of offspring to be produced without the need for conventional sexual intercourse between males and females in captive breeding programmes.

Question 42

What is in vitro fertilisation (IVF)?

Answer 42

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

Question 43

What are the risks of a species population size decreasing?

Answer 43

The risks to a species if its population size decreases will result in reduced genetic variation. This means the species will become more susceptible to environmental changes and is less resilient and has a greater risk of extinction.