Energy Transfer And Nutrient Cycles

Question 1

What is an ecosystem?

Answer 1

All the organisms living in a particular area and all the non-living conditions.

Question 2

What are producers?

Answer 2

Organisms that make their own food - e.g. plant and algae via photosynthesis

Question 3

What are the sugars produced during photosynthesis used for?

Answer 3

In respiration to release energy

To make other biological molecules

Question 4

What is Biomass?

Answer 4

The chemical energy stored in the plant / the mass of living material

Question 5

When is energy transferred through living organisms?

Answer 5

When organisms eat other organisms.

Question 6

Produces are eaten by…

Answer 6

Primary consumers who are then eaten by secondary consumers.

Question 7

How can biomass be measured?

Answer 7

Mass of carbon or the dry mass of its tissue per unit area

Question 8

What is dry mass?

Answer 8

The mass of the organism with the water removed.

Question 9

How can you measure dry mass?

Answer 9

A sample of the organism is dried in an oven at a low temp

Sample weighed at regular intervals, once it becomes constant, you know the water has been removed

Kg m-2

Question 10

What is 50% of dry mass?

Answer 10

The mass of carbon

Question 11

How can you estimate the amount of chemical energy in biomass?

Answer 11

Sample of dry biomass is burnt and the energy released is used to heat a known volume of water - change in temp measured.

Question 12

What is GPP?

Answer 12

The total amount of chemical energy converted from light energy by plants in a given area.

Question 13

What is respiratory loss and how much usually is it?

Answer 13

50% of the GPP is lost to the environment as heat when the plants respire.

Question 14

What is NPP?

Answer 14

The remaining chemical energy.

Question 15

NPP =

Answer 15

GPP - R

Question 16

What is the NPP?

Answer 16

The energy available for plant growth and reproduction.

Question 17

What are herbivores?

Answer 17

Animals that eat plants.

Question 18

What are decomposers?

Answer 18

Organisms which break down dead or indigestes material, allowing nutrients to be recycled.

Question 19

Each of the stages in a food chain is called…

Answer 19

A tropic level.

Question 20

What do the lines (going left to right) show on a food chain?

Answer 20

“Eaten by”

Question 21

What do farming practices aim to do?

Answer 21

Increase the amount of energy that is available for human consumption - increase the efficiency.

Question 22

How do farming practices increase the efficiency of energy transfer? (2)

Answer 22

• the energy lost to other organisms can be reduced e.g. to pests.
• the energy lost through respiration can be reduced.

Question 23

Simplifying the food web means…

Answer 23

Getting rid of pests.

Question 24

How can farmers reduce pests using chemical pesticides? (2)

Answer 24

• using pesticides that kill pests which eat and damage crops - less biomass lost - NPP greater.
• herbicides milk weed, less competition with the crop for energy from the sun.

Question 25

How can farmers use biological agents to reduce the number of pests? (2)

Answer 25

• parasites used to kill the insect or reduce its ability to function.
• pathogenic bacteria and virus are used to kill pests.

Question 26

How can farmers increase the NPP of their livestock?

Answer 26

By controlling the conditions they live in so more energy is used for growth and less is lost through respiration

E.g. restrictions their movements, keeping them inside = more food at a shorter space of time, lower cost. (More biomass produced and more chemical energy can be stored)

Question 27

Enhancing NPP production of animals raises…

Answer 27

Ethical concerns.

Question 28

How are nutrients lost when crops are harvested?

Answer 28

Crops take in minerals from the soil as they grow, they’re harvested and removed so the mineral ions are not returned to the soil by decomposers.

Question 29

When are phosphates and nitrates lost from the system?

Answer 29

When animals or animal products are removed from the land - animals eat grass, taking in nutrients then they are moved away and the nutrients aren’t replaced.

Question 30

What do Fertilisers do?

Answer 30

Replace the lost minerals, so more energy from the ecosystem can be used for growth - increasing efficiency.

Question 31

What are Artificial Fertilisers?

Answer 31

They are inorganic - contain pure chemicals as powders or pellets.

Question 32

What are Natural Fertilisers?

Answer 32

Organic matter including manure, composed vegetables, crop residues and sewage sludge.

Question 33

What is Leaching?

Answer 33

When water soluble compounds in the soil are washed away into nearby ponds and rivers - leads to Eutrophication.

Question 34

Why do Fertilisers raise environmental issues?

Answer 34

• changes the balance of nutrients in the soil.

- leaching is more likely to occur just before heavy rainfall

Question 35

Eutrophication:

Answer 35

• mineral ions leached from fertilised fields stimulate the rapid growth of algae in ponds and rivers.
• large amounts of algae block light from reaching plants below, plants die.
• bacteria feed on dead plant, increased bacteria reduce oxygen concentration in by water by carrying out aerobic respiration.
• not enough oxygen for fish and other aquatic organisms, die.