Harnessing biology

Question 1

Advantages of organic fertilisers

Answer 1

Improves soil structure
Greater range of minerals
Releases minerals over a longer period of time.
Less costly for farmer (already available on farm)

Question 2

Disadvantages of organic fertilisers

Answer 2

Slow acting - has to decompose first
Bulkier, harder to apply to soil than inorganic
May contain pests

Question 3

Advantages of inorganic fertilisers

Answer 3

Fast acting - mineral ions release immediately
Contents known
Easy to apply

Question 4

Disadvantages of inorganic fertilisers

Answer 4

Can lead to eurtophication as fertiliser is soluble
Requires regular reapplication

Question 5

Advantages of pesticides

Answer 5

Easily accessible and relatively cheap
Have an immediate effect
Kills the entire population of pests

Question 6

Disadvantages of pesticides

Answer 6

Pests can develop resistance to them.
Non specific chemicals so can often kill other beneficial organisms (pollinating insects)
Chemicals can concentrate and accumulate at the top of the food chain, harming top predators.
Need for regular application so costly.

Question 7

What pesticide kills insect pests?

Answer 7

Insecticides

Question 8

What pesticide kills plant pests?

Answer 8

Herbicides

Question 9

What pesticide kills fungal pests?

Answer 9

Fungicides

Question 10

Give a brief description of how biological control happens

Answer 10

A species is introduced specifically to prey on the pest species. They never completely remove a pest, but keep it at lower levels. This can happen naturally.

Question 11

Advantages of biological control

Answer 11

Pest will not become resistant.
Can target specific species, will only kill the pest.
Does not need to be repeatedly applied as organism will reproduce.
Long lasting.
Natural method - no pollution.

Question 12

Disadvantages of biological control

Answer 12

Takes a long time to reduce pest population.
Cannot kill an entire population, some pests will always be present.
May not adapt to new environment.

Question 13

Benefits of fish farming

Answer 13

Ability to selectively breed fish to ensure high-quality, fast-growing fish.
Can protect against predators.
Ability to control water quality.
Ability to control feeding to ensure rapid growth.

Question 14

Explain how water quality is managed in fish farming

Answer 14

Water is filtered to remove waste and harmful bacteria to prevent diseases. Water is also cleaned to maintain high levels of oxygen for aerobic respiration.

Question 15

Explain how diseases are controlled during fish farming

Answer 15

Antibiotics are given to fish to prevent spread of diseases which could otherwise spread quickly due to their close confinement. Kept in small numbers to minimise spread of disease. Higher chances of survival.

Question 16

Explain how removal of waste products is used in fish farming

Answer 16

Water can be filtered to remove waste products such as faeces and sewage. Fences, nets, tanks are cleaned or location of fish is changed to ensure clean water.

Question 17

Explain how quality and frequency of feeding is used in fish farming

Answer 17

Food is high in nutrients to ensure fast growth.
Fed frequently but in small amounts so they don’t overeat or start eating each other.

Question 18

Explain how selective breeding is used in fish farming

Answer 18

Fish are separated by gender so farmers can choose to only allow fish with desired characteristic to reproduce (selective breeding). Ensures that the stock of fish is fast growing as these genes get passed on more frequently.

Question 19

Define interspecific predation

Answer 19

Predation between different species.

Question 20

Explain how interspecific predation is controlled in fish farming

Answer 20

Different species of fish are separated by fences, nets and tanks to prevent fighting.

Question 21

Define intraspecific predation

Answer 21

Predation within the same species

Question 22

Explain how intraspecific predation is controlled in fish farming

Answer 22

Fish are separated by size and age so they don’t eat each other or fight.

Question 23

Explain how deforestation leads to leaching

Answer 23

Water is no longer taken up by plants and so begins to ‘run off’ from the soil into rivers and lakes. This water contains dissolved mineral ions (otherwise absorbed by the plant). Mineral ions are removed from the soil (loss of nutrients) and some cause eutrophication

Question 24

Explain how deforestation leads to soil erosion

Answer 24

Water running off deforested areas may carry away topsoil leading to erosion. Due to deforestation, less roots in soil so topsoil is not held in place. Topsoil is most fertile, mineral ion rich so when it is lost, land is difficult to use for crop growth and reduces chances of plants re-growing.

Question 25

Explain how deforestation can lead to droughts

Answer 25

Plants carry out transpiration. The evaporated water from transpiration moves into atmosphere and eventually makes rain. Deforestation breaks this cycle so water doesn’t end up in the atmosphere so rain doesn’t occur. Leads to droughts.

Question 26

Explain eutrophication

Answer 26

Nitrates are absorbed by the green algae in the water.
They multiply rapidly and may cover surface of water. This is called algal bloom.
This blocks out the sunlight for other plants in the lake/river.
The plants can’t photosynthesise so they die.
The algae on top eventually die.
The dead remains provide food for bacteria. The bacteria multiply rapidly.
Large population of bacteria respire increasing biological oxygen demand (B.O.M), using up oxygen in the water.
Decreases level of oxygen in the water and results in the death of other organisms in the water as they cannot respire aerobically.

Question 27

Explain how sewage pollutes water

Answer 27

Sewage provides a good source of food for the bacteria. The bacteria multiply rapidly. Large population of sewage respire increasing B.O.D, using up oxygen in the water. This decreases the level of oxygen and results in the death of other organisms in the water, as they cannot respire aerobically.

Question 28

Explain how greenhouses and polythene tunnels provide enhanced conditions for plants to grow

Answer 28

Transparent material allows natural light in for sufficient photosynthesis.
Greenhouse effect raises temperature.
Burning fossil fuels or wood increases temperature when external temperature is too low, also provides carbon dioxide and water vapour.
Water vapour maintains a moist atmosphere so reduces water loss by transpiration.
This increases rate of photosynthesis so increases the yield.

Question 29

Benefits of selective breeding

Answer 29

Desirable characteristics emerge faster.
Humans can choose desirable characteristics.

Question 30

Problems with selective breeding

Answer 30

Population is more susceptible to disease.
Reduces variation.