23.3 Recycling Within Ecosystems

Question 1

Decomposition

Answer 1

Chemical process where a compound is broken down into smaller molecules or its constituent elements

Question 2

Decomposer

Answer 2

Organism that feeds on and breaks down dead plant or animal matter

Question 3

What does a decomposer do?

Answer 3

Turn organic compounds into inorganic ones

Question 4

What kind of organisms are decomposers?

Answer 4

Saprotrophs - obtain energy from dead or waste organic material

Question 5

How do decomposers break down food?

Answer 5

Secrete enzymes onto dead organisms
Enzymes break down complex organic molecules into simpler soluble molecules
The decomposer absorbs these nutrients

Question 6

Detritivores

Answer 6

Speed up decay process by feeding on detritus - break it down into smaller pieces to increase SA

Question 7

Why is nitrogen important?

Answer 7

Making amino acids and proteins

Nucleic acids

Question 8

When can nitrogen be used by plants?

Answer 8

Needs to be combined with O2 and H2

Question 9

Examples of nitrogen fixing bacteria

Answer 9

Aztobacter and Rhizobium

Question 10

How do nitrogen fixing bacteria work?

Answer 10

Contains enzyme nitrogenase - combines N2 with H2 to form ammonia NH3

Question 11

Where are aztobacter found?

Answer 11

In the soil - it’s a free living soil bacterium

Question 12

Where are rhizobium found?

Answer 12

Inside root nodules of leguminous plants such as peas, beans and clover

Question 13

Symbiotic mutualistic relationship between rhizobium and the plant

Answer 13

Plant gains amino acids from rhizobium by fixing N2

Bacteria gains carbohydrates produced by the plant during photosynthesis (used as energy source)

Question 14

Nitrification

Answer 14

Process where ammonium compounds are converted into nitrogen containing molecules that can be used by plants
Free living bacteria in the soil called nitrifying bacteria are involved

Question 15

In what conditions does nitrification take place?

Answer 15

Oxidation reaction so occurs in well aerated soil

Question 16

Two steps of nitrification

Answer 16

Nitrifying bacteria such as nitrosomonas oxidise ammonium compounds into nitrites (NO2-)
Nitrobacter oxidise NO2- into NO3- (nitrates)

Question 17

Denitrification

Answer 17

In the absence of oxygen (waterlogged soils), denitrifying bacteria convert nitrates in the soil back to nitrogen gas
Occurs in anaerobic conditions
Bacteria use nitrates as a source of energy for respiration to produce N2

Question 18

Ammonification

Answer 18

Process by which decomposers convert nitrogen containing molecules in dead organisms, faeces and urine into ammonium compounds

Question 19

Why is carbon important?

Answer 19

Component of all major organic molecules such as fats, carbohydrates, and proteins

Question 20

How is CO2 returned to the atmosphere?

Answer 20

There us some dissolved in seas and oceans
Combustion
Respiration of plants and animals
Decomposition

Question 21

How are fossil fuels formed?

Answer 21

When living organisms die, carbon compounds are released through decomposition
If dead organic matter accumulates in areas without decomposers, carbon becomes trapped and eventually form fossil fuels

Question 22

Why do CO2 levels fluctuate?

Answer 22

Photosynthesis only takes place during the day, remove CO2
Respiration takes place day and night
CO2 levels are higher at night than during the day

More photosynthesis on a warmer day - less CO2 in atmosphere

Question 23

Why have atmospheric CO2 levels increased over the last 200 years?

Answer 23

Combustion of fossil fuels

Deforestation - less photosynthesis, burning of felled trees

Question 24

How does temperature affect CO2 dissolved in seas?

Answer 24

Higher temperatures - less CO2 dissolved

Reduce carbon bank in the oceans and more CO2 in the atmosphere