ecosystems

Question 1

what is an individual organism

Answer 1

a single organism

Question 2

what is a population

Answer 2

all the organisms of one species in a habitat

Question 3

what is a community

Answer 3

all the organisms of different species living in a habitat

Question 4

what is an ecosystem

Answer 4

a community of organisms along with all the non-living conditions

Question 5

explain how communities can be affected by abiotic factors: temperature, light, water, pollutants

Answer 5

temperature = ex distribution of birds is changing because of rise in average temperature = travel to different countries
light = some species can only cope with certain light intensities
water = ex daisies grow best in slightly damp soil, if too waterlogged population of daisies decreases
pollutants = ex too high concentrations of sulfur dioxide

Question 6

explain how communities can be affected by biotic factors - competition

Answer 6

• organisms compete with other species and members of their own species for the same resources

Question 7

explain how communities can be affected by biotic factors - predation

Answer 7

• as number of predators decrease number of prey might increase because less are being hunted by predators

Question 8

Describe the importance of interdependence in a community

Answer 8

• organisms depend on each other for things like food and shelter in order to survive and reproduce = interdependence
• a change in the population of one species has knock on effects for other species in the same community

Question 9

Describe how the survival of some organisms is dependent on
other species, including parasitism

Answer 9

parasites live closely with host species and take what it needs to survive without the host benefitting

Question 10

Describe how the survival of some organisms is dependent on
other species, including mutualism

Answer 10

relationship between two organisms where both benefit

Question 11

Core Practical: Investigate the relationship between organisms
and their environment using field-work techniques - belt transects

Answer 11

belt transects study the distribution along a gradient
1. mark a line in area of study
2. collect data using quadrats placed next to each other
a) if quadrat id long place at regular intervals
b) collect data by counting organisms of the species or by estimating percentage cover (estimating percentage area of quadrat covered by a particular type of organism)
3. record data such as mean height or abiotic factors in each quadrat ex using light meter to measure light intensity
4. repeat steps 1 and 2 and find mean number of organisms or mean percentage cover for each quadrat
5. plot graphs to see if the changing abiotic factor is correlated with a change in the distribution of the species your studying

Question 12

Core Practical: Investigate the relationship between organisms
and their environment using field-work techniques, including
quadrats

Answer 12

a quadrat is a frame enclosing a known area to compare how common an organism is in two sample areas
1. place a 1msquared quadrat at a random point within the first sample area
a) you could divide sample area into a grid using a random number generator to pick coordinated to place your quadrat sat to make sure your results are representative of the whole quadrat area
2. count all the organisms you’re interested in within the quadrat
3. repeat steps 1 and 2 lots
4. work out mean number of organisms per quadrat within the first sample area
a) mean = total number of organisms / number of quadrats
5. repeat steps 1 - 4 in the second sample area
6. compare the two means

Question 13

estimate population sizes

Answer 13

• in one sample are work out the mean number of organisms per m squared
• then multiply mean by the total area of the habitat

Question 14

Explain the positive and negative human interactions within
ecosystems and their impacts on biodiversity
a) fish farming

Answer 14

• reduce biodiversity
  1. food is added to nets to feed fish which produces lots of waste and both the food and waste leaks into the open water causing eutrophication
  2. fish farms in open water act a breeding ground for large numbers of parasites which get out of the farm and infect wild animals
  3. predators are attracted to nets and become trapped in them
  4. farmed fish can escape into the wild which can cause problems for wild populations of indigenous species

Question 15

Explain the positive and negative human interactions within
ecosystems and their impacts on biodiversity
b) introduction of non-indigenous species

Answer 15

• non indigenous species = one that doesn’t naturally occur in an area
  1. non indigenous species compete with indigenous species for resources like food and shelter and they could out compete the indigenous species which decrease the number and reduces biodiversity
  2. could also bring new diseases to a habitat which can infect and kill lots of indigenous species and reduce the habitat’s biodiversity

Question 16

Explain the positive and negative human interactions within
ecosystems and their impacts on biodiversity
c) eutrophication

Answer 16

• nitrates are put onto fields as fertilisers if too much fertiliser is applies and it rains afterwards nitrates go into rivers and lakes
• resulting in eutrophication = an excess of nutrients in water leading to deaths of species and reducing biodiversity
  1. fertilisers adding excess nitrate
  2. causes algae to grow fast and block out light
  3. plants can’t photosynthesise and die
  4. more food is now available and microorganisms that feed on decomposing plants increase and use up oxygen in the water
  5. organisms that need oxygen for aerobic respiration die

Question 17

what is biodiversity

Answer 17

variety of living organisms in an ecosystem

Question 18

Explain the benefits of maintaining local and global biodiversity
a) conservation of animal species

Answer 18

• protects biodiversity by preventing species from dying out
• protecting a species’ natural habitat
• protecting species safe areas outside of their natural habitat and introducing captive breeding programmes to increase numbers
• use of seed banks to store and distribute seeds or rare and endangered plants

Question 19

Explain the benefits of maintaining local and global biodiversity,
b the impact of
reforestation

Answer 19

• forests have a high biodiversity as they contain a wide variety of trees and plants
• reforestation restores biodiversity from deforestation
• need to be carefully plans to maximise positive effects and minimise negative ones

Question 20

Describe how different materials cycle through the abiotic and
biotic components of an ecosystem

Answer 20

• living thing are made of elements they take from the environment
• which they turn into complex compounds that make up living organisms
• elements are passed along food chains when animals eat the plants and each other
• elements are recycled - waste products and dead organisms are broken down into decomposers and the elements in them are returned to the soil and air to be taken by new plants and put back into the food chain

Question 21

explain the process of the carbon cycle

Answer 21

• powered by photosynthesis, green plants use carbon from co2 to make carbohydrates, fats and proteins
• eating passes the carbon compounds in the plant along to animals in a food chain
• plant and animal respiration while the organisms are alive releases co2 back into the air
• plants and animals die and decompose or are turned into useful products or kills
• when they decompose they’re broken down by microorganisms such as bacteria and fungi which release co2 back into the air by respiration as they break down the material
• some useful plant and animal products are burned which releases co2 back into the air
• decomposition of material means that habitats can be maintained for the organisms that live there

Question 22

what is the role or microorganism in the carbon cycle as decomposers

Answer 22

• release co2 back into the air by respiration as they break down the material
• decomposition of material means that habitats can be maintained for the organisms that live there

Question 23

Explain the process of the water cycle

Answer 23

• energy from the sun makes water evaporate to water vapour
• water also evaporates from plants in transpiration
• warm water vapour is carried upwards as warm air rises and when it gets higher up it cool and condenses to form clouds
• water falls from the clouds as precipitation onto land (where it provides fresh water)
• then drains into sea and repeats

Question 24

explain the production of potable water in areas of drought through desalination

Answer 24

• desalination removes salts (mineral ions) from salt water
• thermal desalination boils water in an enclosed vessel so that water evaporates and steam rises to the top of the vessel but the salt stays at the bottom, the steam travels down a pipe from the top of the vessel and condenses back into pure water

Question 25

when does a drought occur

Answer 25

not enough precipitation

Question 26

explain how reverse osmosis desalinates water

Answer 26

• salt water is treated to remove solids before being fed at a high pressure into a vessel with a partially permeable membrane
• the pressure causes the water molecules to move in the opposite direction to osmosis from a higher salt concentration to a lower salt concentration
• water is forced through membrane and the slats are left behind and removed

Question 27

what is the importance of the water, carbon and nitrogen cycle

Answer 27

how the fixed amount is recycled

Question 29

explain how fertilisers make nitrates available for plant uptake

Answer 29

• spread animal manure or compost on fields recycles the nutrients left in plant and animal waste and returns them to the soil through decomposition
• artificial fertilisers containing nitrates can be used

Question 30

explain how crop rotation uses nitrates made available for plant uptake

Answer 30

• different crops are grown each year in a cycle using nitrogen-fixing crops which helps put nitrates back into the soil for another crop to use the following year

Question 31

explain how the role of bacteria in the nitrogen cycle makes nitrates available for plant uptake

Answer 31

• decomposers break down proteins in rotting plants and animals and urea in animal waste
• this returns nitrogen into the soil so the nitrogen in these organisms is recycled

Question 32

what is nitrogen fixation and use of lightning

Answer 32

• turning nitrogen from the air into nitrogen-containing ions in the soil which plants can use
  a) lightning - so much energy in a bolt of lightning that is makes nitrogen react with oxygen in the air giving nitrates

Question 33

What are the different types of bacteria involved in the nitrogen cycle
a) decomposers

Answer 33

a) decomposers - decompose proteins and urea and turn them into ammonia
ammonia forms ammonium open in solution that plants can use

Question 34

What does nitrifying bacteria do in the nitrogen cycle

Answer 34

Turns ammonia in decaying matter into nitrites and then into nitrates

Question 35

What does nitrogen fixing bacteria do in the nitrogen cycle

Answer 35

Turns atmospheric nitrogen into ammonia which form ammonium ions

Question 36

What does denitrifying bacteria do in the nitrogen cycle

Answer 36

Turns nitrates back into nitrogen gas
To no benefit of living organisms
Denitrifying bacteria are often found in waterlogged soils