Energy and ecosystems

Question 1

What is a producer?

Answer 1

Photosynthetic organisms that manufacture organic substances using light energy, water, carbon dioxide and mineral ions

Question 2

What is a consumer?

Answer 2

Organisms that obtain their energy by feeding on other organisms

Question 2

What are saprobionts?

Answer 2

Decomposers are a group of organisms that break down the complex materials in dead organisms into simple ones releasing minerals and elements (fungi and bacteria)

Question 3

What is a trophic level?

Answer 3

Each stage in a food chain

Question 4

What do the arrows on food chain diagrams show?

Answer 4

The direction of energy flow

Question 5

What is biomass?

Answer 5

Total mass of living material in a specific area at a given time

Question 6

How is chemical energy in dry mass estimated?

Answer 6

Calorimetry

Question 7

What is gross primary production (GPP)?

Answer 7

The total quantity of the chemical energy store in a plant in a given are/volume at a given time

Question 8

How much of their chemical energy to plants use in respiration?

Answer 8

20-50%

Question 9

What is net primary production?

Answer 9

GPP- respiration losses

Question 10

What is NPP used for?

Answer 10

Plant growth and reproduction

Question 11

How much energy do primary consumers use for growth from NPP of producers?

Answer 11

<10%

Question 12

Why is such a low percentage of energy transferred at each stage?

Answer 12

Some of the organism not consumed, some cannot be digested (faeces), some lost in excretory materials (urine) and some energy losses occur as heat from respiration and lost to the environment

Question 13

How is net production of consumers calculated?

Answer 13

N = I - (F+R)
net production = chemical energy stored - (respiration + faeces and urine loss)

Question 14

Why do most food chains have only 4 or 5 trophic levels?

Answer 14

The inefficiency of energy transfer between trophic levels

Question 15

What are the four main stages in the nitrogen cycle?

Answer 15

Ammonification, nitrogen fixation, nitrification and denitrification

Question 16

What is denitrification?

Answer 16

Nitrates within the soil are converted to gaseous nitrogen by anaerobic bacteria

Question 17

What is ammonification?

Answer 17

Release of ammonium ions from DOM

Question 18

What is nitrification?

Answer 18

Aerobic oxidation of ammonium ions to nitrite then nitrate ions by bacteria

Question 19

What is nitrogen fixation?

Answer 19

Converting nitrogen gas into compounds (by lightning, free-living bacteria or symbiotic bacteria)

Question 20

How does phosphate mostly exist?

Answer 20

Mostly as phosphate ions PO4 3-

Question 21

How does phosphate move through the cycle?

Answer 21

Geological uplifting bring it out of the sea and into land, then weathering and erosion makes them available for uptake or guano from seabirds

Question 22

What are mycorrhizae and what do they do?

Answer 22

Fungi networks between plant roots, help to resist drought and take up inorganic ions

Question 23

What does mycorrhizae receive from the plant?

Answer 23

Sugars and amino acids

Question 24

What are the environmental effects of nitrogen fertilisers?

Answer 24

Reduced species diversity, leaching and eutrophication

Question 25

How do nitrogen fertilisers reduce species diversity?

Answer 25

Nitrogen rich soils favour the growth of nettles, grasses and other rapidly-growing species which may out-compete other species

Question 26

Why is eutrophication bad?

Answer 26

Lead to algal blooms the stop light entering the water body, this means photosynthetic organisms under the water will die and decompose under anaerobic conditions, oxygen content of the water will drop and consumers with suffocate.

Question 27

What happens to phosphate ions not absorbed by the plants?

Answer 27

Washed away by rain and end up in lakes, rivers and seas