Ecosystems

Question 1

What is a habitat?

Answer 1

The place where an organism lives e.g. a rock shore or a field

Question 2

What is a population?

Answer 2

All the organisms of one species in a habitat

Question 3

What is a producer?

Answer 3

An organism that produces organic molecules using sunlight energy, e.g. plants

Question 4

What is a consumer?

Answer 4

An organism that eats other organisms, e.g. animals

Question 5

What is a decomposer?

Answer 5

An organism that breaks down dead or undigested organic material, e.g. bacteria and fungi

Question 6

What is a trophic level?

Answer 6

A stage in the food chain occupied by a particular group of organisms, e.g. producers are the first trophic level in a food chain.

Question 7

What is an ecosystem?

Answer 7

A complex dynamic, self perpetuating assemblage of organisms interacting in their biotic and abiotic enviornment.

Question 8

What are biotic factors?

Answer 8

The living features of an ecosystem e.g the presence of predators, disease, competition ect

Question 9

What are abiotic factors?

Answer 9

The non-living features of an ecosystem e.g. the temperature, rainfall, shape of land (topology) and soil nutrient availability

Question 10

What is net productivity?

Answer 10

The amount of energy available to the next trophic level

Question 11

What is biomass?

Answer 11

The mass of living material

Question 12

What happens to energy locked up in food webs and chains?

Answer 12

Gets locked up in things that can’t be eaten (e.g. bones and faeces), and is recycled back into the ecosystem by decomposers.

Question 13

Rock pools: What are the biotic factors?

Answer 13

Seaweed can be a food source for consumers such as limpets that graze on this producer. Intense competition for food (such as seaweed) can limit the number of organisms that are present in a small pool ecosystem .

Question 14

Rock pools: What are the abiotic factors?

Answer 14

Rock pools are heavily influenced by tides. At high tide they are completely submerged by the ocean so simialr abiotic factors (e.g. pH, salinity, temperature, ect.) to the ocean ecosystem. However, at low tide they experince more extreme abiotic conditions (e.g. higher salinity and temperatures)- only some organisms can tolerate these conditions.

Question 15

Playing field: What are the biotic factors?

Answer 15

Producers include grass and other plants such as daises, clover and dandelions. The large amount of these plants will attract a large number of organisms that use them for a food source (e.g. rabbits and caterpillars ect).

Question 16

Playing field: What are the abiotic factors?

Answer 16

Rainfall and sunlight affect the growth of the producers in the ecosystem. In a very wet year, the soil may become waterlogged, making it difficult for plants to grow. Poor plant growth may decrease the number of consumers the ecosystem is able to support.

Question 17

Large tree: What are the biotic factors?

Answer 17

Insects, such as caterpillars, can use the leaves of a tree as a source of food. However, if they consume all the leaves on a tree (defoliation) they can slow the growth of the tree and even lead to its death.

Question 18

Large tree: What are the abiotic factors?

Answer 18

Drought conditions (e.g. when there are prolonged periods of very low rainfall) can negatively impact the growth of a tree. In severe cases it can result in the whole tree dying.

Question 19

How much of the total energy is lost in various ways through a food chain?

Answer 19

90%

Question 20

How much of the available energy is never taken in by the organisms?

Answer 20

60%

Question 21

Reasons that not all the available energy is taken in by the organisms?

Answer 21

• Plants can’t use all the light energy that reaches their leaves e.g. some is the wrong wavelength, some is reflected, and some passes straight through the leaves.
• Some sunlight can’t be used because it hits part of the tree that doesn’t photosynthesise e.g. the bark of the tree.
• Some parts of food e.g. bone or roots, aren’t eaten by organisms so energy isn’t taken in- they pass to decomposers
• Some parts of food are indigestible so pass through organisms and come out as waste e.g. faeces - they pass to decomposers.

Question 22

What is gross productivity?

Answer 22

The rest of the energy that is available and taken in (40% of total available energy).

Question 23

How to calculate the net productivity?

Answer 23

Gross productivity (energy absorbed)- respiratory loss

Question 24

How is efficency of energy transfered measured between producers and primary consumers calculated?

Answer 24

(Net productivity of primary consumers/ net productivity of producers) x100

Question 25

How is efficency of energy transfered measured between primary consumers and secondary consumers calculated?

Answer 25

(Net productivity of secondary consumer/ net productivity of primary consumer) X 100

Question 26

How to calculate the efficency of biomass transfer between trophic levels?

Answer 26

Efficency of transfer= (biomass transfered/ biomass intake) x100
Biomass transfered= biomass that has passed to the higher trophic level
Biomass intake= biomass of the lower level that has been consumed

Question 27

Livestock farmers can use these methods for primary consumers (grazers)?

Answer 27

• May be kept in warm indoor pens where their movement is restricted. Less energy is wasted keeping warm and moving around.
• May be given feed that’s higher in energy than their natural food. This increases the energy input, so more energy is available for growth

Question 28

Arable farmers can use these methods for producers?

Answer 28

• Herbicides kill weeds that compete with agricultural crops for energy. Reducing competition means crops recieve more energy, so they grow faster and become larger, increasing productivity.
• Fungicides kill fungal infections that damage agricultural crops. The crops use much more energy for growth and less for fighting infection, so they grow faster and become larger, increasing productivity.
• Fertilisers are chemicals that provide crops with minerals needed for growth e.g. nitrates. Crops use up minerals in the soil as they grow, so their growth is limited when they’re aren’t enough minerals. Adding fertiliser replaces the lost minerals, so more energy from the ecosystem can be used to grow, increasing the efficency of energy conversion.

Question 29

Nitrogen cycle: What is nitrogen fixation?

Answer 29

When nitrogen gas in the atmopshere is turned into ammonia by bacteria such as Rhizobium and Azotobacter. The ammonia can then be used by plants.

Question 30

Nitrogen cycle: Where is Rhizobium found?

Answer 30

Found inside the root nodules (growth on the roots) of leguminous plants (e.g. peas, beans and clover).
They form a symbiotic relationship with the plants- they provide the plant with amino acids and nitrates and the plant provides them carbohydrates.

Question 31

Nitrogen cycle: Where is Azotobacter found?

Answer 31

Found living in the soil

Question 32

Nitrogen cycle: What is ammonification?

Answer 32

When nitrogen compounds from dead organisms are turned into ammonia by decomposers, which goes on to form ammonium ions.
Animal waste (urine and faeces) also contain nitrogen compounds. These are also turned into ammonia by decomposers and go onto form ammonium ions.

Question 33

Nitrogen cycle: What is nitrification?

Answer 33

When ammonium ions in the soil are changed into nitrogen compounds that can be used by plants (nitrates).
- First nitrifying bacteria called Nitrosomonas change ammonium ions into nitrates.
- Then other nitrifying bacteria Nitrobacter change nitrites into nitrates.

Question 34

Nitrogen cycle: What is denitrification?

Answer 34

When nitrates in the soil are converted into nitrogen gas by denitrifying bacteria- they use nitrates in the soil to carry out respiration and produce nitrogen gas.
- This happens under anaerobic conditions (when there’s no oxygen), e.g. in waterlogged soils

Question 35

Nitrogen cycle: What other ways does nitrogen get into an ecosystem?

Answer 35

Lightning (which fixes atmospheric nitrogen) or by artifical fertilisers (they’re produced from atmospheric nitrogen on an industrial scale called the Haber process).

Question 36

What is primary succession?

Answer 36

This happens on land that has been newly formed or exposed, e.g. when a volcano has erupted to form new surface rock, or where sea level has dropped exposing a new area of land. There’s no soil or organic matter to start with e.g. just bare rock.

Question 37

What is secondary succession?

Answer 37

This happens on land that has been cleared of all plants, but where soil remains, e.g. after a forest fire or where a forest has been cut down by humans.

Question 38

What is succession?

Answer 38

This is the process by which an ecosystem chnages over time. The biotic conditions (e.g. plant and animal communites) chnage as the abiotic conditions change (e.g. water availability).