Topic 9 - Ecosystems and Material Cycles

Question 1

Define a species

Answer 1

A group of similar organisms that can reproduce with one another to make fertile offspring

Question 2

Define a population

Answer 2

All the members of the same species within the same habitat

Question 3

Define a niche

Answer 3

An organism’s role

Question 4

Define an ecosystem

Answer 4

The interaction of abiotic and biotic factors

Question 5

Define a community

Answer 5

All the different populations within a habitat

Question 6

Define a habitat

Answer 6

A place where an organism lives

Question 7

Define an organism

Answer 7

An individual living thing

Question 8

Explain how communities can be affected by the abiotic factor of temperature

Answer 8

Temperature affects the rate of photosynthesis.
Living things have evolved to grow healthily at their optimum temperature and could not survive in different conditions.

Question 9

Explain how communities can be affected by the abiotic factor of water

Answer 9

Living things require water to survive. If plant roots are waterlogged they are unable to respire, they rot and the plant dies. Plants vary in the mositure levels that they require.

Question 10

Explain how communities can be affected by the abiotic factor of light

Answer 10

Light is required for photosynthesis. The rate of photosynthesis affects the rate at which the plant grows. Plants can be food sources or shelter for many organisms.
Some plants have evolved for optimum growth in certain light intensity.

Question 11

Explain how communities can be affected by the abiotic factor of pollutants

Answer 11

Air pollutants such as sulfur dioxide are released from the burning of fossil fuels. Lichens cannot survive if the concentration of sulfur dioxide is too high.

Question 12

Explain how communities can be affected by the biotic factor of competition

Answer 12

If one species is better adapted to the environment than another, then it will outcompete it until the numbers of the lesser adapted species are insufficient to breed.

Question 13

Explain how communities can be affected by the biotic factor of predation

Answer 13

New predators can upset the balance of the habitat of a balanced ecosystem where predator and prey have evolved together.

Question 14

Describe interdependence in a community

Answer 14

Interdependence describes how organisms in a community depend on other organisms for vital services.
This could include food, shelter or reproduction.

Question 15

Describe parasitism

Answer 15

A parasite is an organism that lives and feeds on another organism, called its host. The host is harmed in the relationship while the parasite benefits.

Question 16

Describe mutualism

Answer 16

Both species in a relationship benefit

Question 17

Describe the core practical to investigate the relationship between organisms and their environment using field-work techniques, including quadrats and belt transects

Answer 17

-Divide a field into a numbered grid with equally sized squares.
-Place a quadrat in a random square
-Count the number of the object/plants there are within the quadrat
-Repeat this with other random squares (5-15)
-Compare results by calculating a mean.
-Multiply the mean by how many squares there are to discover how many of the object/plants there are in the whole grid

Question 18

What is the calculation for population size based on quadrats?

Answer 18

Population size = mean number of organisms in quadrant x total size of area where organism lives/total area of quadrats

Question 19

Define a producer

Answer 19

An organism that makes its own food

Question 20

Define a primary consumer

Answer 20

A herbivorous organism that eats plants for energy

Question 21

Define a secondary consumer

Answer 21

A carnivorous or omnivorous organism that eats primary consumers for energy

Question 22

Define a decomposer

Answer 22

An organism that breaks down or eats decaying material as its energy source

Question 23

Explain energy transfers between trophic levels

Answer 23

The stages in a food chain or web are called trophic levels.
Energy/biomass is transferred between each trophic level. It transfers into less useful forms at each trophic level, which affects the number of organisms at each level and limits the length of the food chain.

Question 24

What are the reasons for energy loss between trophic levels?

Answer 24

-Energy lost as heat to the environment
-Energy used as metabolism
-Energy lost in faeces/urine

Question 25

What is the calculation for efficiency of biomass transfers?

Answer 25

Energy transferred to biomass/total energy supplied to organism

Question 26

Evaluate fish farming

Answer 26

Pros: -Fish farms are ways of raising large numbers of fish in a small space to provide food for humans Cons: -Overfishing reduces biodiversity and can lead to the endangerment of some species

Question 27

Evaluate the introduction of non-indigenous species

Answer 27

Pros: -Can be used to remove pests or for hunting Cons: -The new species may out-compete or kill indigenous or naturally occurring species. These may be reduced in number, resulting in reduced biodiversity or maybe extinction

Question 28

Explain eutrophication

Answer 28

Chemicals used in farming leak into the environment, if they leak into a lake this can cause eutrophication - excessive growth of plant life. This can deplete the body of water of oxygen, making it less able to sustain other species - such as fish.

Question 29

Explain the benefits of maintaining local and global biodiversity through conservation of animal species and the methods

Answer 29

-Breeding programs to help preserve endangered species, like the panda and stop them becoming extinct -Protection and development of new endangered habitats, often by making National Parks, to stop the species there becoming extinct or regenerate a species to encourage populations to live here -Replanting hedgerows because there is higher biodiversity in them than in the fields they surround and they provide areas where wild flowers and grasses can grow

Question 30

Explain the methods for maintaining local and global biodiversity through reforestation to combat environmental issues

Answer 30

-Reducing deforestation and the release of greenhouse gases, reduces the rate of global warming and slows down the rate that habitats are destroyed -Reforestation, planting trees to replace those cut down -Recycling rather than dumping waste in landfill sites, reduces the amount of land taken up for landfills, and slows the rate we are using up natural resources

Question 31

Describe the biological factors affecting levels of food security

Answer 31

-Increasing human population and birth rate, more food is required -Increasing animal farming and the increased meat and fish consumption, already low food resources are even more scarce as demand increases -The impact of new pests and pathogens, can destroy crops -Environmental change caused by human activity, causes climate change which can affect food production e.g. drought -Sustainability issues, e.g. use of land for biofuel production and the increased cost of agricultural inputs (farming costs)

Question 32

Describe how carbon dioxide is removed from the atmosphere in the carbon cycle

Answer 32

-Carbon dioxide is removed from the air through photosynthesis in plants and algae. The carbon becomes part of proteins, fats and carbohydrates

Question 33

Describe how carbon dioxide is returned to the atmosphere in the carbon cycle

Answer 33

-Organisms eat a plant and the carbon becomes part of fats, carbohydrates and proteins in the animal -Organisms respire, releasing carbon dioxide into the atmosphere -Decomposers feed on dead organisms and waste materials from animals, consuming the carbon -Organisms are fossilised and eventually become fossil fuels. Carbon dioxide is released by the combustion of fossil fuels

Question 34

Describe the water cycle

Answer 34

-The sun's energy causes water to evaporate from bodies of water, forming water vapour -Water vapour is also formed from transpiration in plants -Water vapour rises and condenses to form clouds -Water is returned to the land by precipitation, which runs into lakes to provide for plants and animals, this then runs into seas and the cycle begins again (surface runoff), infiltration may also occur

Question 35

What is the order of the water cycle?

Answer 35

ECTPIST Evaporation, Condensation, Transport, Precipitation, Infiltration, Surface runoff, Transpiration

Question 36

Define infiltration as part of the water cycle

Answer 36

Water that has fallen as precipitation is absorbed into the ground. This can be stored within underground rocks called aquifers

Question 37

Describe desalination

Answer 37

In desalination, salt and other minerals/impurities from seawater is removed to make it drinkable.

Question 38

Why must water be filtered?

Answer 38

-To remove objects

Question 39

Why must water be treated with chemicals?

Answer 39

To destroy pathogens and to make it taste better

Question 40

Describe distillation of water

Answer 40

Evaporate the water , then condense the water vapour to form pure water

Question 41

Describe reverse osmosis of water

Answer 41

Salt water is forced at high pressure into a vessel with a partial permeable membrane. The pressure causes water molecules to move in the opposite direction of osmosis, from a concentrated salt solution to a lower sat concentration (higher water concentration). Water molecules pass across the membrane, leaving the salt behind, so that pure water is available for drinking

Question 42

Describe the nitrogen cycle

Answer 42

-Decomposers break down waste matter into ammonia through decomposition/ammonification -Nitrifying bacteria convert ammonia into nitrites and then nitrates through nitrification -Nitrogen-fixing bacteria convert nitrogen gas in the air into nitrates through nitrogen fixation -Denitrifying bacteria convert nitrates into nitrogen gas through denitrification

Question 43

How can nitrate concentration of soil be increased to make nitrates available for plant uptake through crop rotation?

Answer 43

Crops such as peas, beans or clover can form nitrate, as they have nitrogen-fixing bacteria in their roots. This will increase the nitrate content and fertility of the soil. Crops will take in the nitrate and use it to make proteins for growth. One year the farmer will grow crops that can form nitrate, and the next year plant another crop in the nitrate rich soil.

Question 44

How can nitrate concentration of soil be increased to make nitrates available for plant uptake through the use of fertilisers?

Answer 44

Natural fertilisers such as manure or compost or artificial fertilisers such as ammonium nitrate provide a source of nitrate to increase crop yield, as the nitrate is used to make proteins for growth.

Question 45

Evaluate the use of indicator species as evidence to assess the level of pollution in polluted water

Answer 45

Polluted water is identified by the presence of bloodworms or sludge worms. Sludgeworms show high pollution and blood worms show moderate pollution.

Question 46

Evaluate the use of indicator species as evidence to assess the level of pollution in clean water

Answer 46

Clean water is identified by the presence of freshwater shrimps or stonefly. Stonefly nymph show clean water and freshwater shrimps show some pollution.

Question 47

Evaluate the use of indicator species of lichen as evidence to assess the level of pollution in air quality

Answer 47

Clean air provides an ideal environment for a rich variety of lichens. Lichen is less likely to be found in areas where the air is heavily polluted with sulfur dioxide. Bushy lichens need clean air, leafy lichens can survive a small amount of air pollution, crusty lichens can survive in more polluted air.

Question 48

Evaluate the use of indicator species of a specific fungi as evidence to assess the level of pollution in air quality

Answer 48

Rose blackspot fungus is more likely to be found in less polluted areas, as sulfur dioxide protects plants from certain fungi.

Question 49

Explain the effects of temperature availability on the rate of decomposition in food preservation

Answer 49

At colder temperatures decomposing organisms will be less active, therefore the rate of decomposition remains low, increasing the temperature increases the rate of decay. At extremely high temperatures decomposers will be killed and decomposition will stop.

Question 50

Explain the effects of temperature availability on the rate of decomposition in composting

Answer 50

When decomposers break compost down, the compost heap becomes warmer due to the respiration of the bacteria and fungi generating heat.

Question 51

Explain the effects of water content availability on the rate of decomposition in food preservation and composting

Answer 51

With little or no water there is less decomposition because decomposers cannot survive. As the volume of available water increases, the rate of decomposition also increases. Many decomposers secrete enzymes onto decaying matter and then absorb any dissolved molecules. Without water these reactions cannot occur.

Question 52

Explain the effects of oxygen availability on the rate of decomposition in food preservation and composting

Answer 52

Most decomposers respire aerobically, therefore oxygen is required. This why we often seal food in bags or cling film. As the volume of available oxygen increases, the rate of decomposition also increases.

Question 53

What is the calculation for rate changes in the decay of biological material?

Answer 53

rate of decomposition = change in value(usually mass)/time taken