chapter 20

Question 1

Describe the methods of how humans have increased food production

Answer 1

1. Agriculture machinery ( replaces humans and improves efficiency due to the ability to farm much larger areas
2. Chemical fertilizer ( fertilisers increase the amount of nutrients in soil , improves yield )
3. Insecticide ( kills of unwanted insects and pest to improve quality and yield )
4. Herbicide ( reduce weeds from other plant species, reduce competition )
5. Selective breeding ( to produce high yield and quality )

Question 2

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

Answer 2

A:
easier to manage
more efficient
promote technological advances in agriculture
offers higher earnings

D:
reduces biodiversity
causes extinction of species
Disrupts food chain
Soil erosion and flooding
increase pest population
problems with insecticides and pesticides ( harmless insects killed , pollution , pests become resistant to them , reducing effectiveness )

Question 3

Describe the advantages and disadvantages of
intensive livestock production

Answer 3

A:
helps economy and agricultural industry
provides food security

D:
Reduction in biodiversity ( areas where large amounts of land are used to graze cattle only grass is grown so becomes monoculture )
Overgrazing lead to soil erosion
Production of large amounts of methane
Disease can spread
Waste from cattle can pollute waterways , eutrophication

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

1. clearing land for farming and housing ( cleared due to increase in human population and demand in food )
2. Extraction of natural resources ( mining of coal, logging for paper , wood )
3. Freshwater and marine pollution
   • oil spills and other waste pollute ocean and kills aquatic life
   • Eutrophication occurs in waterway caused by leaching of fertilizers
   • Reduces biodiversity

Question 6

Explain the undesirable effects of deforestation

Answer 6

1. Habitat destruction, Extinction and loss of biodiversity
2. Soil erosion
3. Flooding and landslide
4. Increase CO2 in atmosphere

Question 7

Describe reasons why forests are cut down

Answer 7

For building/land
for cattle farming, land needed for cattle to graze
Planting of monoculture
mining of coal
wood for paper , furniture

Question 8

Describe the effects of untreated sewage and excess fertiliser

Answer 8

Eutrophication

Question 9

Explain the process of eutrophication of water

Answer 9

1. Runoff of fertilisers from farmland enters the water
2. This causes increased growth of algae known as algae bloom
3. Algae blocks off sunlight causing waterplants and algae to die
4. Decomposing bacteria increases in number, increase respiration
5. Bacteria uses up dissolved oxygen
6. as a result, less oxygen in water, aquatic organism like fish are unable to survive and will die

Question 10

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

Answer 10

In aquatic :
- Animals eat plastic or become caught in it and choke to death
- As the plastic breaks down it releases toxins which affect marine organisms

On land :
- Plastic is buried in land fills and as it breaks down , toxins are released into soil
- visual pollution

Question 11

Describe the sources and effects of pollution of
the air by methane and carbon dioxide

Answer 11

Sources of methane : cattle farming, decomposition of organic matter
Sources of CO2 : produce during combustion of fossil fuels, burning of trees during deforestation

Effect : Both are a greenhouse gas which means contribute to global warming
Increase in greenhouse gases , increases:
1. greenhouse effect, causing Earth’s average temperature to rise

Question 12

Describe the consequences of global warming due to enhanced greenhouse effect

Answer 12

Ocean temperature increases causing:
1. melting of polar ice caps > rising of sea levels > flooding

increase temperature can causes extreme weather like :
super storms
drought
desertification
forest fires

Extreme weather leads to :
loss of habitat
decrease in biodiveristy
food chain disrupted, extinction of species
increase in migration of species resulting in spread of pests and disease

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

Answer 14

1. replanting / reforestation
2. education of the importance of forests
3. Rules , regulation, quotas
4. Fines for illegal deforestation
5. Protected areas like forest reserves or nature parks

Question 15

Explain how fish stocks can be conserved

Answer 15

1. Controlling number of fish caught each year ( quotas )
2. Controlling age and size of fish caught ( to ensure enough fish and of suitable age for breeding )
3. Controlling the time of year fish can be caught ( to prevent large scale decrease of stocks )
4. Captive breeding
5. Educate locals and fishermen ( on local and international laws, so they are aware of type of fish that are not produced sustainably )
6. Protected areas ( exclusive zones, nursery zones )
7. Laws and regulation ( prevent overfishing or illegal fishing )
8. Fish nets ( good size holes )

Question 16

Explain why organisms become endangered or extinct

Answer 16

• over-hunting
  climate change
  pollution
  loss of habitat
  introduction of non-native species that outcompete native species

Question 17

Describe how endangered species can be conserved

Answer 17

education programmes
captive breeding programmes
monitoring and legal protection of the species and their habitats
seed bank ( where endangered seeds are carefully stored so that plants may be grown in the future )

Question 18

Describe the reasons for conservation programmes

Answer 18

1. reducing extinction rates
2. keeping damage to food chains and web to a minimum
3. protecting of vulnerable ecosystems
4. protecting future food supply
5. maintaining the nutrient cycles and possible sources of future medical drugs and fuels

Question 19

Describe artificial insemination

Answer 19

1. sperm inserted into vagina and into the uterus using catheter when female is ovulating
2. females may be given hormones to super ovulate

Question 20

Describe in vitro fertlisation aka IVF

Answer 20

1. needle inserted into female’s ovaries and egg extracted
2. eggs kept in culture medium
3. male sperm is mixed with the egg so fertilisation can occur
4. Several zygotes form and develop into embryo
5. the embryos are placed in a culture for several days
6. the embryos are transferred into the mother

Question 21

Explain the risks to a species if its population size decreases

Answer 21

When population size decreases, species are at risk because there is less or no variation which reduces the rate of reproduction. This leads to lesser offsprings and eventually the entire species is extinct

Question 22

Describe the basic process of sewage treatment

Answer 22

1. Screening
   - large materials , removed and burned
2. Sedimentation
   - where solid materials settles at the bottom at sludge
   - liquid part called effluent on top
3. The sludge / organic waste
   - removing by pumping it into tanks where anaerobic bacteria decompose it
   - bacteria often produces methane which can be collected and used as a biofuel source for the plant
4. The effluent
   - treated with aerobic bacteria to remove any organic waste in it
   - b4 being treated with bacteria to kill the bacteria.