B9 | ecosystems & material cycles

Question 1

what is food security?

Answer 1

having access to enough food that is safe to eat and has the right balance of nutrition

Question 2

role of photosynthesis in the carbon cycle

Answer 2

• plants take in carbon dioxide by photosynthesis

- plants make carbon compounds (glucose) from carbon dioxide

Question 3

role of respiration in the carbon cycle

Answer 3

• plants release carbon dioxide during respiration
• plants are eaten by animals
• carbon from plants is passed to animals
• animals release carbon dioxide during respiration

Question 4

role of decomposition in the carbon cycle

Answer 4

• microorganisms feed on dead plants and animals

- microorganisms release carbon dioxide during respiration and decomposition

Question 5

role of combustion in the carbon cycle

Answer 5

• fossil fuels are formed from dead plants and animals
• fossil fuels contain stored carbon
• carbon dioxide is released into the atmosphere during combustion

Question 6

what effect does burning fossil fuels have on the environment?

Answer 6

• causes an increase in carbon dioxide and other greenhouse gases
• heat is blocked from radiating back into space causing global temperature to increase (global warming)
• loss of biodiversity e.g. glaciers melting, loss of habitats

Question 7

what is desalination?

Answer 7

the process of removing mineral ions (like sodium) from salt water to make it potable (drinkable)

Question 8

water cycle

Answer 8

1) precipitation: rain, hail, sleet and snow falls from clouds producing freshwater for organisms
2) condensation: water vapour cools and turns into clouds
3) transpiration: evaporation and diffusion of water from the leaves of trees/plants
4) groundwater flow: when water flows through the rocks and soil underground
5) surface run-off: when water runs off the surface of the ground
6) evaporation: when the sun heats up water from the oceans and it goes up into the atmosphere

Question 9

how does reverse osmosis work?

Answer 9

moves water into purification tanks under high pressure (water molecules move against concentration gradient)

water is forced through a partially permeable membrane leaving behind/removing salts from the water

Question 10

role of decomposers in the nitrogen cycle

Answer 10

• decomposers are bacteria which breaks down dead organic matter
• they convert proteins into urea and ammonia
• ammonia is released into soil
• this increases nitrogen in the soil

Question 11

role of nitrifying bacteria in the nitrogen cycle

Answer 11

• nitrifying bacteria converts ammonia into nitrites
• nitrites are then converted into nitrates
• which absorbed by plants to make proteins

Question 12

role of nitrogen-fixing bacteria in the nitrogen cycle

Answer 12

• nitrogen-fixing bacteria turn atmospheric nitrogen into ammonia and ammonium ions under aerobic conditions
• found in the soil and in the root nodules of leguminous plants
• mutualistic relationship: plants protect bacteria from predators and bacteria provide nitrites to make proteins
• roots absorb nitrites by active transport

Question 13

role of denitrifying bacteria in the nitrogen cycle

Answer 13

• converts nitrates back into nitrogen gas
• this happens when soil becomes waterlogged and occurs under anaerobic conditions
• increases the amount of nitrogen in the atmosphere

Question 14

what is decomposition?

Answer 14

natural process of the breakdown of dead plant and animal matter/waste into simpler molecules such as carbon dioxide, water and mineral ions (carried out by bacteria or fungi)

Question 15

how does temperature affect the rate of decomposition?

Answer 15

• high temperature = enzymes in microorganisms work faster/at optimum temperature & microorganisms reproduce faster
• temperature TOO high = denature of enzymes
• low temperature = enzymes don’t have enough energy to make reactions occur fast enough

Question 16

how does oxygen availability affect the rate of decomposition?

Answer 16

microorganisms need oxygen for cell respiration

Question 17

how does water availability affect the rate of decomposition?

Answer 17

decomposers need water to survive, reproduce and carry out biological processes

Question 18

what is compost?

Answer 18

decomposed organic matter that is used as a natural fertiliser for crops and gardens – it recycles nutrients back into the ecosystem – improving plant growth

Question 19

why do we freeze/refrigerate food?

Answer 19

decreases the temperature which prevents microorganisms from reproducing/stops enzymes from working (decreases rate of decomposition)

Question 20

why do we dehydrate food?

Answer 20

reduces water availability for microorganisms which prevents them from reproducing and surviving (decreases rate of decomposition)

Question 21

why do we store food in cans?

Answer 21

airtight cans prevents oxygen/new microorganisms from getting inside which prevents decomposition/reproduction (decreases rate of decomposition)

cans are also sterilised

Question 22

why do we store food in salt water?

Answer 22

microorganism loses water due to osmosis (water moves from area of high concentration [organism/food] to area of low concentration [salt water]) which decreases rate of decomposition

Question 23

why do we store food in oil?

Answer 23

prevents oxygen from getting to microorganisms which decreases rate of transpiration

Question 24

how do fish farms in open water reduce biodiversity?

Answer 24

• food is added to nets to feed the fish which produces large amounts of waste
• this food and waste can leak into the water causing eutrophication/death of wild species
• fish farms in open water acts as a breeding ground for parasites which can infect both the fish and animals outside the farm
• predators such as sea lions are attracted to the farms, they can get caught in the nets and die
• fish can escape and cause problems for indigenous species

Question 25

how does the introduction of non-indigenous species impact biodiversity?

Answer 25

- non-indigenous species compete with indigenous species for food and shelter - sometimes the non-indigenous species are better at getting these resources and out-compete the indigenous species - this causes a decrease in the indigenous species and eventually they die out - non-indigenous species can also bring new diseases to a habitat where the indigenous species cannot survive them

Question 26

how does eutrophic impact biodiversity?

Answer 26

- fertilisers containing nitrates are added to land and after it rains, they can run off into rivers and lakes - fertilisers add excess nitrates into the water which causes algal bloom which blocks sunlight - plants are unable to photosynthesise due to lack of sunlight and eventually they die and decompose - microorganisms which feed on dead plants now have more food, therefore they multiply faster and use up all the oxygen in the water - organisms that need oxygen for aerobic respiration die

Question 27

how does the increase in animal farming and consumption of meat/fish affect food security?

Answer 27

grazing animals are fed food such as corn and wheat which could instead be eaten by humans overfishing means there won’t be enough fish to catch in the future

Question 28

how do environmental changes caused by human activity affect food security?

Answer 28

burning fossil fuels releases lots of carbon dioxide which traps energy in the atmosphere leading to global warming global warming is a type of climate change which would then affect the growth of crops soil pollution also affects the growth of crops

Question 29

how does sustainability affect food security?

Answer 29

space which could be used to grow crops to eat is being used to grow crops for biofuel increase in farming costs makes it too expensive for farmers to continue farming in the future

Question 30

how do new pests and pathogens affect food security?

Answer 30

they can cause damage to crops and livestock

Question 31

what do bloodworms and sludgeworms indicate about water quality?

Answer 31

polluted water

Question 32

what do stoneflies and freshwater shrimps indicate about water quality?

Answer 32

clean water

Question 33

what do large amounts of bushy lichen and black spot fungus indicate about air quality?

Answer 33

clean air

Question 34

what do crusty lichen indicate about air quality?

Answer 34

polluted air