Ecosystems and Material Cycles

Question 1

What is an abiotic factor?

Answer 1

An abiotic factor is a non-living factor.

Question 2

What are some abiotic factors that affect a community?

Answer 2

Abiotic factors that affect a community:
light intesnity
temperature
moisture levels
soil pH and mineral content
wind intensity and direction
carbon dioxide levels
oxygen levels

Question 3

What is a biotic factor?

Answer 3

A living factor

Question 4

What are some biotic factors that affect a community?

Answer 4

Biotic factors that affect a community:
food availability
new predators
new pathogens
competition

Question 5

What is interdependence?

Answer 5

Interdependence describes how organisms in a community depend on other organisms for vital service.
This could include: food, shelter and reproduction(pollination, seed dispersal).

For example: Birds take shelter in trees, flowers are pollinated with the help of bees.
The removal or addition of a species to a community can affect the population of others greatly, as it changes preys or predators.

Question 6

What is a stable community?

Answer 6

A stable community is one where all the biotic and abiotic factors are in balance. As a result, the population sizes remain roughly constant.

Question 7

What is parasitism?

Answer 7

Parasitism involves taking nutrients from another species, whilst negatively affecting the other. For example: In humans, the tapeworm is a parasite that lives inside the gut. It “steals” nutrients from the host and can lead to malnutrition.

Question 8

What is mutualism?

Answer 8

Mutualism is when there is no damage caused to either species, and there is often a mutual benefit. For example: algae and fungi live together to form lichens. Algae can photosynthesise to provide sugars for the fungi , whereas the fungi allows the algae to live in more extreme conditions than those under which it would normally thrive.

Question 8

CORE PRACTICAL - Fieldwork and Counting Organisms:

Answer 8

We can determine the number of organisms in a given area using fieldwork techniques, and tools such as quadrats and transects.
How to determine the biodiversity in an area:
-Measure/Count every single (wanted) plant in the field.
This would be time consuming and there would be a high likelihood of an error.

OR

-Take a sample of the (wanted) plant from a small area and use this to estimate the entire population of it.

This would significantly take less time and with less risk of error. To carry out this experiment you must:
1) Divide the field into 100 equal 1m x 1m squares.
2) Use a random generator to randomly select a single square.
3) Take a 1m x 1m quadrat and place it in the selected square.
4) Count the number of clovers in the square.
5) Repeat with a different square 4 more times and average the results.
6) Multiply the average by 100 to estimate the number of (wanted) plants in the field.

Question 9

What is the calculation efficiency of Energy Transfers:

Answer 9

(Biomass transferred to the next level/Biomass available) x 100

Question 10

What is positive human interactions with the ecosystems?

Answer 10

• Maintaining rainforests, ensuring habitats are not destroyed.
• Raising awareness among the public about how to protect ecosystems.
• Reducing water pollution and monitoring the changes over time.
• Replanting hedgerows and woodlands to provide habitats which were previously destroyed.

Question 11

What are some negative interactions with the ecosystems?

Answer 11

• Production of greenhouse gases leading to global warming.
• Introducing non-indigenous species into the environment, which prey on native species.
• Producing sulfur dioxide in factories which leads to acid rain- affects habitats.
• Clearing land in order to build on, reducing the number of habitats
• Chemicals used in farming leak into the environment- if they leak into a lake, this can cause eutrophication which can deplete the body of water (making it less able to sustain other species such as fish).
• Overfishing which reduces biodiversity and can lead to endangerment of some species.

Question 15

How to maintain biodiversity?

Answer 15

• Reduction of deforestation and carbon dioxide production: reduces the rate of global warming, slowing down the rate that habitats are destroyed.
• Recycling rather than dumping waste in landfills: reduce the amount of land being taken up by landfills, and slows the rate we are using up natural resources.
• Breeding programs: to stop endangered species from becoming extinct.
• Protection of rare habitats.
• Reintroduction of hedgerows and field margins: provides habitats for lots of organisms and provides areas where wild flowers and grasses can grow.

Question 16

What is food security?

Answer 16

Food security: having sufficient amount of food to feed a population.

Question 17

What are some factors affecting levels of Food Security?

Answer 17

Factors:
1) Increasing birth rate and human population, meaning more food is required.
2) Changing diets in developed countries means food resources which are already low in amount become even more scarce as the demand for them increases.
3) New pests and pathogens can destroy crops.
4) Climate change affects food production. Such as no rain resulting in crops failing.
5) Conflicts in some countries can affect the availability of water and Food.

Question 18

Explain the carbon cycle? (3)

Answer 18

1) CO2 is removed from the air in photosynthesis by green plants and algae- they use the carbon to make carbohydrate, proteins and fats. They are eaten and the carbon moves up the food chain.
2) CO2 is returned to the air when plants, algae and animals respire. Decomposers(a group of organisms that break down dead organisms and waste) respire while they return mineral ions to the soil.
3) CO2 is returned to the air when wood and fossil fuels are burnt (combustion) as they contain carbon from photosynthesis.

Question 19

What happens with the decomposition of biological material producing compost?

Answer 19

When biological material decays it produces compost. It is used by gardeners and farmers as a natural fertiliser. To do this they have to provide optimum conditions for decay:
-If more oxygen is available they respire aerobically, producing heat.
-The increased temperature increases the rate of decay so the compost is made quicker.

Question 20

How to produce methane gas?

Answer 20

Microorganisms decompose waste anaerobically to produce methane gas. This can be burnt as a fuel. Biogas generators are used to produce methane:
This requires a constant temperature(3o degrees) so the microorganisms keep respiring. It cannot be stored as a liquid so needs to be used immediately.

Question 21

Describe the water cycle (6)

Answer 21

1) The suns energy causes water to evaporate from the sea and lakes forming water vapour.
2) Water Vapour is also formed as a result of transpiration in plants.
3) Water Vapour rises and then condenses to form clouds.
4) Water is returned to the land by precipitation(rain, snow) and this runs into lakes to provide water to plants and animals.
5) This then runs into seas and the cycle begins again.
6) In areas of drought, we can harness the water cycle to produce potable water.. For example, desalination is the process by which we remove salt and other minerals/impurities from sea/water to make it drinkable. It is performed by a process called reverse osmosis and generally occurs on a large scale.

Question 22

Describe the use of nitrates in plants

Answer 22

-Nitrogen gas in the atmosphere is too unreactive so cannot be used directly by plants.
-Nitrogen-fixing bacteria present in the root nodules of legume plants convert nitrogen gas into nitrates that can be used for growth
-Plants absorb nitrates through the roots by active transport.
-Lightning can convert nitrogen gas into nitrates.
-The Haber process converts the hydrogen gas into ammonia.
-Nitrogen is often included in fertilisers in the form of ammonium nitrate. This provides an artificial way to ensure plants that plants get nitrates required for growth, without relying on external processes such as nitrogen-fixing bacteria or lightning.

Question 23

Nitrogen is often included in fertilisers in the form of ammonium nitrate. This provides an artificial way to ensure plants that plants get nitrates required for growth, without relying on external processes such as nitrogen-fixing bacteria or lightning.

Answer 23

Sometimes it is too expensive to assess how polluted an area is in great great detail and so in these cases we can use an indicator species to assess population levels

Question 24

How is polluted water identified?

Answer 24

Polluted water is often identified by the presence of bloodworms or sludge worms.

Question 25

How is clear water identified?

Answer 25

Clean water often harbours freshwater shrimps and stonefly. The presence of these species is indicative of clean, unpolluted water.

Question 26

How is air quality identified?

Answer 26

Air quality can be indicated by a number of species of lichen. In areas where the air is heavily polluted with sulfur dioxide, lichen is less likely to be found. Clean air often provides an ideal environment for a variety of lichens. The rose blackspot fungus is more likely to be found in less polluted areas, as sulfur dioxide protects plants from certain fungi.

Question 27

What are some factors affecting rate of Decomposition of Food and Compost:

Answer 27

Temperature: Chemical reactions generally work faster in warmer conditions, but if is too hot the enzymes can denature and stop decomposition.

Water: Microorganisms grow faster in conditions with water as it is needed for respiration. Water also makes it easier to digest.

Availability of oxygen: Most decomposers respire aerobically.
Particularly in compost:
If more oxygen is available, they respire aerobically, producing heat. Increased temperature increases the rate of decay, so the compost is made quicker.

Question 28

CORE PRACTICAL - Investigate the effects of temperature on decay

Answer 28

You can investigate the effects of temperature on decay by measuring the pH change of fresh milk in the presence of enzyme lipase:
1) Make a solution of milk and phenolphthalein indicator.
2) Add sodium carbonate which will cause the solution to become alkaline and therefore pink.
3) Place the tube in a water bath at a specific temperature.
4) Add the lipase enzyme and begin stopwatch.
5) Time how long it takes for the pink colour to disappear( when the pH has decreased).
6) Repeat this at different temperatures to see which temperature the pink colour disappears the quickest , indicating the quickest decomposition.