Chapter 19:Human influences on ecosystem

Question 1

how have humans increase food production

Answer 1

1-agricultural machinery to use larger areas of land and improve efficiency
2-chemical fertilisers to improve yields
3-insecticides to improve quality and yield
4-herbicides to reduce competition with weeds
5-selective breeding to improve production by crop plants and livestock

Question 2

how do agricultural machinery increase food production

Answer 2

Agricultural machinery such as tractors allows a farmer to do much more work on the land in a day than using hand tools or machinery pulled by animals

Question 3

how do chemical fertilisers help increase food production

Answer 3

chemical fertilisers containing mineral ions such as nitrate provide extra nutrients to grow crop plants.they grow faster and larger and produce greater yields

Question 4

how do insecticides help increase food production

Answer 4

Chemicals that kill insects can be sprayed onto growing crops to kill pests than feed on the plants.this increases the yield from the crop

Question 5

how do herbicides help increase food production

Answer 5

Chemicals that kill plants can be sprayed onto the crop to kill weeds .this reduces competition between the weeds and the crop plant for resources such as light and water,so the crop plants can grow faster and larger,increasing yield

Question 6

how does selective breeding help increase food production

Answer 6

new varieties of animals and crop plants that grow faster are able to survive better in difficult conditions such as in time of drought

Question 7

Define monocultures

Answer 7

an area of ground covered by a single crop,with almost no other species present

Question 8

advantages of monocultures

Answer 8

1- using Machinery to cultivate a large, uninterrupted area of land can be done more quickly and efficiently than tending several small separate fields
2-a uniform crop, is likely to grow the same height and ripen at the same time, so it can all be harvested at once
3-A large area of the same crop can all be treated with the same herbicides and pesticides
4-A monoculture will probably produce large quantities of seed, fruits, or other harvestable parts that are all uniform in size and quality, make it easier for the farmer to market

Question 9

disadvantages of monocultures

Answer 9

1- the biodiversity is low as only few species can live where the crop is growing
2-increase of pests and transfer viruses
3-reduction in soil fertility

Question 10

Advantages of intensive farming

Answer 10

1-help provide more food for people
2-takes up less land than extensive farming

Question 11

Disadvantages of intensive farming

Answer 11

1-there can be welfare issues for the livestock,which may suffer in the crowded conditions in which they are kept
2- diseases can spread easily among them
3-the waste from intensive farming unit can pollute land and waterways nearby
4-foods for the animal is often produced from food that we could eat ourselves
5-energy is used to transport feed to the livestock often over very long distances
6-large quantities of water may need to be provided if large number of animals are kept in one place

Question 12

Why are habitats destroyed

Answer 12

-to provide more land for farming and housing
-to extract natural resources,such as mineral or fossil fuels
-by adding pollutants to the environment

Question 13

Define biodiversity

Answer 13

The number of different species that live in an area

Question 14

What are the effects of deforestation

Answer 14

• loss of habitat
  -loss of soil
  -increase flooding
  -increase carbon dioxide in the atmosphere

Question 15

how does deforestation cause loss of habitat

Answer 15

Plants and animals that live in forests have adaptions that allow them to live there. They may not survive when the forest is cut down and this could result in extension of species

Question 16

how does deforestation cause loss of soil

Answer 16

Plant roots help to hold soil in place, especially on slopes.when trees are lost soil is easily eroded by wind or water

Question 17

how does deforestation cause increased flooding

Answer 17

With no trees,rain water hits the ground directly,and is likely to run off rather than soak gently into the soil. Also there is no tree rooted to take up water from the ground

Question 18

how does deforestation cause an increase carbon dioxide in the atmosphere

Answer 18

no tree means no photosynthesis to remove carbon dioxide from the air.if the trees are brunt,this produces more carbon dioxide

Question 19

What are the two most important greenhouse gases

Answer 19

-carbon dioxide
-methane

Question 20

What is the green house effect

Answer 20

The heating effect on the earth of the trapping of heat by greenhouse gases

Question 21

explain eutrophication process

Answer 21

1- the extra nutrients such as nitrates increase and completely cover the water surface
2-the producers on the water surface prevent light reaching plants growing below them,so they cannot photosynthesis and die
3-the dead plants provide food for decomposers and the number of decomposers increase
4-many decomposers respire aerobically and use up most of the oxygen dissolved in the water
5-animals in the water now do not have enough oxygen so they move away and die

Question 22

What’s the effect of untreated sewage and excess fertilisers on aquatic ecosystem

Answer 22

-untreated sewage may contain pathogens from humans and so can spread diseases such as cholera or polio
-both untreated sewage and fertilisers contain nutrients that increase plant growth if they enter rivers,lakes or the sea.this can cause algal blooms.the algae may produce toxins that can kill animals that drink the water

Question 23

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

Answer 23

-Non-biodegradable plastics plastics that cannot be broken down by decomposes.when they have been thrown away they remaining environment for a long time.
-Land animals, such as mice, may enter plastic bottles, and get trapped
-Sea turtles mistake them for jellyfish and eat them. This can block the alimentary canals of the turtles so that they cannot absorb nutrients and eventually die.

Question 24

what is conservation

Answer 24

Looking after the natural environment and tries to maintain or increase the biodiversity

Question 25

describe a sustainable resource

Answer 25

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

Question 26

How can forests be conserved

Answer 26

1- governments can refuse to grant license to companies who want to cut down valuable forests
2-leaving enough of the trunk to allow the tree to regrow
3-only cut down some trees so that the forest can regenerate from seeds prosecuted by remaining trees
4-replanting trees when they are cut down
5-educating people to make sure they understand important it is to conserve forests
6-protect places by law so that people are not allowed to cut down trees in that area

Question 27

how does selective felling damage the forest

Answer 27

-the roads that are built to allow access
-the large machinery that is used to drag the timber out
-the disturbance caused by the people working in the forest

Question 28

how can fish stock be conserved

Answer 28

1-drawing up international agreements about where different countries are allowed to fish and how many fish they can take
2-limiting the areas and times the fishermen are allowed to take fish
3-ensuring the nets have a wide mesh
4-imposing quotas so that there is a limit of fish a boat is allowed to catch
5-using a license or permit for boats allowed to fish
6-Reducing demand for wild fish
7-Using petrol boards to ensure that fishing boats are obeying the rules and imposing severe penalties for breaking the rules
8-Educating people about fish stock
9-Breeding fish increase numbers and then releasing them into the environment

Question 29

Why are organisms becoming endangered or extinct

Answer 29

-climate change
-human destruction
-hunting
-pollution
-introduced species

Question 30

How can endangered species be conserved

Answer 30

-monitoring and protecting species and habitats
-eduction
-seed banks
-captive breeding programmes

Question 31

how does captive breeding help conserving endangered species

Answer 31

keeping animals in captivity allow them to breed in order to to increase the numbers in the population

Question 32

how does seed banks help in conserving endangered species

Answer 32

facilities in which seeds of different plant species or crop varieties are stored for long period of time in order to conserve as many different species and varieties as possible

Question 33

reasons for conservation programmes

Answer 33

-Maintaining or increasing biodiversity
-reducing extinction
-protecting vulnerable ecosystem
-maintains g ecosystem functions

Question 34

Describe the use of artificial insemination in captive breeding

Answer 34

artificial insemination involves taking semen from the male and inserting it into the vagina of the female.some of the sperm in the semen will find their way to an egg and fertilise it.the zygote will then develop into an embryo and implant into the uterus in the normal way

Question 35

Describe the use of vitro fertilisation in captive breeding

Answer 35

-It involves Collecting eggs from the female,placing them in a sterile liquid in a sterile container and then adding seaman from the male.fertilisation happens in the dish and several zygotes formed.
-some of these then divide to form tiny embryos and are placed in the female uterus with the hope that it will implant in a normal way,grow into a fetes and eventually be born successfully

Question 36

Explain the risks to a species if it’s population size decreases reducing genetic variation

Answer 36

This makes a species much more likely to become extinct, especially if environmental condition changes.
When to individuals breed together the may each carry the same harmful recessive allele of a gene. Some of their offspring may therefore inherit this harmful allele from each parent, and consequently have a homozygous recessive genotype, which produces a phenotype, making them less likely to survive