Energy and ecosystems

Question 1

In any ecosystem plants synthesis organic molecules from…

Answer 1

atmospheric or aquatic carbon dioxide

Question 2

Name two things sugars produced by the plant is used for

Answer 2

• Used as respiratory substrate

- Used to make other biological molecules

Question 3

Define biomass

Answer 3

Total mass of living material. Biomass can be measured in terms of mass of carbon or dry mass of tissue per given area.

Question 4

What is GPP

Answer 4

Gross primary production (GPP) is the chemical energy store in plant biomass, in a given area or volume.

Question 5

What NPP

Answer 5

Net primary production (NPP) is the chemical energy store in plant biomass after respiratory losses to the environment have been taken into account

Question 6

Equation for NPP

Answer 6

NPP= GPP-R

Question 7

What can NPP energy be used for

Answer 7

Plant growth and reproduction

Question 8

What do N, I, R and F stand for

Answer 8

N- net production of consumers
I- chemical energy store in ingested food
F- chemical energy lost to the environment in faeces and urine
R-represents the respiratory losses to the environment in faeces

Question 9

Name the stages of the nitrogen cycle

Answer 9

Ammonification
Nitrification
Nitrogen fixing
Denitrification

Question 10

What is ammonification

Answer 10

The production if ammonia from organic nitrogen containing compounds. This is done by saphobiont organisms feeding on dead organisms,

Question 11

What is nitrification

Answer 11

The production of nitrogen containing compounds. This is done by nitrogen fixation and is carried out by free living soil microorgamisms They convert ammonium ions into NO2- and NO3-

Question 12

What is nitrogen fixation

Answer 12

The process of turning nitrogen gas into nitrogen containing compounds. It is done by two types of bacteria: free living nitrogen fixing bacteria and mutualistic

Question 13

Describe what free living nitrogen fixing bacteria do

Answer 13

Reduce gaseous nitrogen to ammonia which they use to produce amino acids. When they die nitrogen rich compounds are released

Question 14

Describe what mutualistic nitrogen fixing bacteria do

Answer 14

They live on the roots of some plants. They obtain carbohydrates from the plant and the plant acquires amino acids from the bacteria

Question 15

What is denitrification

Answer 15

When soils become waterlogged they have low oxygen concentration. This causes an increase in anaerobic denitrification bacteria who convert soil nitrates into gaseous nitrogen.

Question 16

Name a source of phosphate ions

Answer 16

In sedimentary rocks. Due to weathering these ions can dissolve into the soil where they can enter the living part of the P cycle.

Question 17

Name three problems that can arise from using fertilisers

Answer 17

• reduced species diversity (favours certain types of plants)
• leeching (rainwater can causes nitrate ions to enter drinking water sources such as freshwater lakes which can have harmful affects on humans
• eutrophication (run off into lakes causes algae bloom which kills underwater plants as no light, dead plant matter fed on by saprobiontic organisms = more. They use oxygen in respiration + less O2 in water killing any aerobic organisms).