Ecosystems And Material Science

Question 1

Describe the mutualistic relationship between an oxpecker and a herbivore?

Answer 1

• Oxpecker bird benefits by getting food
• Herbivore benefits from the loss of skin parasites

Question 2

Describe the mutualistic relationship between nitrogen fixing bacteria and legumes?

Answer 2

• Nitrogen fixing bacteria in root nodules are protected from environment and get food from plant
• Legume plant gets nitrogen compounds for healthy growth from the bacteria

Question 3

How do you work out the number of organisms in the whole area using quadrats?

Answer 3

Mean number of organism in one quadrat
x
Total area / Area of one quadrat

Question 4

What are the positive and negative effects of fish farming on ecosystems?

Answer 4

Positives:
- Farming reduces fishing of wild fish
Negatives:
- Waste can pollute local area which will change the conditions so local species may die out
- Diseases from farmed fish can spread to wild fish and kill them
- If farmed fish escape they may compete with wild fish for recourses
- Predators of the fish may get trapped in the nets and die

Question 5

What are the positive and negative effects of introducing non-indigenous species to an area?

Answer 5

Positives:
- May provide food for native species
Negatives:
- May reproduce rapidly if they have no predators
- May outcompete native species for resources

Question 6

How does eutrophication affect aquatic environments? (All steps)

Answer 6

• Fertilisers added to fields may leak into rivers, this adds phosphates and nitrates to the water
• This fertiliser causes water plants/algae to grow quickly
• Plants/algae cover the surface of the water and block light to deeper water
• Deeper plants can’t get sunlight so can’t photosynthesise and die
• Bacteria decompose dying plants so they respire, using oxygen from water
• As the water in now anoxic fish die due to lack of oxygen

Question 7

What are four reasons for maintaining biodiversity?

Answer 7

• Moral reasons, humans should respect other living organisms
• Aesthetic reasons, humans enjoy seeing the variety of living organisms
• Ecosystem structure, organisms have important roles such as decaying processes, food chains may be unstable
• Usefulness, some species are particularly useful such as medical drugs or plants grown for crops

Question 8

What are the advantages of reforestation?

Answer 8

• Restores habitat for endangered species
• Reduces concentration of carbon dioxide in the air, photosynthesis
• Tree root bound soil together which reduces the effects of soil erosion
• Affects local climate such as reducing the range of temperature variation

Question 9

What are the different steps in the nitrogen cycle?

Answer 9

• Nitrogen gas in air is converted to nitrate compounds by nitrogen fixing bacteria in root nodules
• Or Nitrogen gas can be ‘fixed’ by lighting then dissolve in rainwater and leach into soil
• Nitrates in the soil are then absorbed by plants and used to make proteins
• Animals eat the plants and consume the nitrates
• Animal death and waste (proteins, urea in urine) put nitrogen back into soil as ammonium compounds (NH)
• Nitrifying bacteria in the soil oxidises the ammonium compounds, turning them into nitrates
• These can then be absorbed by plants and continue the cycle
• In some conditions, denitrifying bacteria is found in soil and this breaks down nitrates and converts it back into nitrogen gas

Question 10

Which species are used to indicate air pollution?

Answer 10

• Lichen, some species can only grow when there’s no pollution, other grow when there is, so the type of lichen on trees is used as an indicator
• Blackspot, a fungus that infects roses, damaged by sulfur dioxide in air so when there is pollution rises are clear of this fungus

Question 11

What are the species used to indicate water pollution?

Answer 11

• Bloodworms and sludgeworms, can live in water containing little oxygen so are found in polluted water
• Stonefly larvae, some mayflies, freshwater shrimps and caddisflies, only live in highly oxygenated water so are indicators of unpolluted water

Question 12

What factors affect the rate of decomposition?

Answer 12

• Warm temperatures as that increases enzyme activity in microorganisms
• Water content as microorganisms need water for many cell processes
• Oxygen availability as microorganisms need oxygen for respiration

Question 13

How do you prevent decay in food?

Answer 13

• Refrigerating as the temperature is too cold for most microorganisms to grow quickly
• Salting as it causes water to move out of bacterial cells by osmosis so there isn’t enough water in the microorganism cells for them to grow
• Packing food in nitrogen as there is no oxygen for microorganisms to respire

Question 14

What is a population?

Answer 14

All the organisms of the same species in an area

Question 15

What is a community?

Answer 15

All the populations in an area

Question 16

What is an ecosystem?

Answer 16

The interaction between a community of living organisms and their environment

Question 17

What are some examples of abiotic factors?

Answer 17

• Light intensity
• Temperature
• Moisture levels of soil (rainfall)
• Soil pH level
• Soil mineral content
• Wind intensity
• Oxygen levels in water
• Carbon dioxide levels for plants
• Levels of pollutants

Question 18

Why do high moisture levels in soil damage some plants?

Answer 18

Their roots are unable to respire, they rot and the plant dies

Question 19

What are some examples of biotic factors?

Answer 19

- Availability of food

• New predators
• New pathogens
• Competition

Question 20

What do plants compete for?

Answer 20

• Light
• Space
• Water and nutrients

Question 21

What do animals compete for?

Answer 21

• Food
• Mates for reproduction
• Territory

Question 22

How do you investigate the relationship between light intensity and organisms?

Answer 22

• Place a tape measure on the ground, from an area of low shade to high shade (transect)
• Place the top left-hand corner of a quadrat at a point on the transect line
• Measure of the light intensity at that point and record
• Record the abundance of the selected plants in the quadrat
• Repeat this at regular intervals along the line

Question 23

What factors affect levels of food security?

Answer 23

• Increase in human population
• Increase in animal farming and the increased meat and fish consumption
• The impact of new pests and pathogens
• Environmental change caused by human activity
• Sustainability issues

Question 24

What are the disadvantages of intensive farming practices?

Answer 24

• Reduction in biodiversity
• Creates pollution
• Risk of antibiotic resistance
• Considered unethical by some people

Question 25

What is an advantage and disadvantage of using biofuels for farming machines?

Answer 25

Advantage:
- Renewable
- Do not contribute as much to global warming

Disadvantage:
- They are grown on land which could be used for growing crops

Question 26

What are the stages of the carbon cycle?

Answer 26

• Carbon enters the atmosphere as CO2 from respiration and combustion
• CO2 is absorbed by produces to make carbohydrates in photosynthesis
• Animals feed on plants, passing the carbon compounds along the food chain
• Most carbon they consume is exhaled as CO2 during respiration
• The animals and plants die
• Dead organisms are eaten by decomposes and carbon in their bodies is returned to the atmosphere of CO2
• When decomposition isn’t possible, they may eventually form fossil fuels

Question 27

What are the stages of the water cycle?

Answer 27

• Evaporation: energy from sun evaporates water
• Condensation: often forming clouds
• Transport: water in clouds transported elsewhere by strong winds
• Precipitation: rain or snow
• Surface runoff: if large volumes of water fall it can run along the surface of the ground into rivers or sea
• Infiltration: precipitation is absorbed into the ground, can be stored in underground rocks
• Transpiration: water evaporates from plants after transpiration

Question 28

What are the disadvantages of distillation?

Answer 28

• Expensive because large amounts of energy are needed to heat the water
• Increases fossil fuels, a nonrenewable resource that contributes to global warming

Question 29

How is water distilled?

Answer 29

• Sea water is boiled
• The water vapour is cooled and condensed to form pure water
• The salt and other impurities are left behind

Question 30

How is water desalinised by osmosis?

Answer 30

Reverse osmosis:
- Salt water is forced at high pressure into a vessel with a partially permeable membrane

• The pressure causes water molecules to move in the opposite direction to osmosis (from concentrated salt solution to a liver salt concentration)
• Water molecules pass across the membrane leaving the salt behind

Question 31

What are the advantages of crop rotation?

Answer 31

• Different crops remove different nutrients from the soil
• Some plants have nitrogen fixing bacteria in their roots so add nitrates back into the soil

Question 32

How do you calculate the rate of decay?

Answer 32

Loss of mass (grams) / Time (days)

Question 33

What conditions should be used to make compost?

Answer 33

• High moisture levels
• Warm
• Aerobic (oxygen present)