5.4 Nutrient Cycles

Question 1

What is extracellular digestion?

Answer 1

Secretion of enzymes outside of an organism and external digestion and only necessary nutrients absorbed

Question 2

What is sabrobiotic nutrition

Answer 2

Obtaining nutrients from dead organic matter using extracellular digestion

Question 3

What are mycorrhizae?

Answer 3

Fungi with symbiotic relationships with roots of plants

Question 4

Why are mycorrhizae so efficient?

Answer 4

• Act like extensions of root system
• Increase S.A for water and ion absorption
• Sponge (store water and soluble minerals and ions)

Question 5

What is nitrogen fixation?

Answer 5

Atmospheric nitrogen is converted into nitrogen containing compounds

Question 6

What carries out nitrogen fixation?

Answer 6

• Free floating nitrogen fixing bacteria

- Mutualistic nitrogen fixing bacteria (root nodules of legumes)

Question 7

What is ammonification?

Answer 7

Production of ammonia from nitrogen containing organic compounds
- Ammonium ions in soil
Usually by saprobionts

Question 8

What carries out ammonification?

Answer 8

Saprobionts

Question 9

What is nitrification?

Answer 9

Ammonium ions are oxidised into other nitrogen compounds that a plant can use

Question 10

What are the intermediates in nitrification?

Answer 10

Ammonium - Nitrite - Nitrate

Question 11

What carries out nitrification?

Answer 11

Nitrifying bacteria which require aerobic conditions

Question 12

What is denitrification?

Answer 12

Nitrates in soil converted to atmospheric nitrogen

Question 13

What carries out denitrification?

Answer 13

Denitrifying bacteria which require anerobic conditions

Question 14

How can atmospheric nitrogen be introduced into an ecosystem?

Answer 14

Lightning, artificial fertilisers (Haber process), nitrogen fixation

Question 15

What is the main phosphorous store?

Answer 15

Sedimentary rock

Question 16

How is phosphorous introduced into an ecosystem?

Answer 16

Weathering of rocks into soil or water bodies

Question 17

Why are nutrients lost when crops are harvested?

Answer 17

• Removed from ecosystem instead of left to die and decompose
• No return of ions by saprobionts to the soil
• No replace from remains or waste products

Question 18

What are the types of fertilisers?

Answer 18

Artificial - Inorganic and contain pure chemicals

Natural - Organic matter such as manure, compost, sewage sludge, guano

Question 19

What are some environmental issues related to fertiliser usage?

Answer 19

• Excess used = leaching and eutrophication

- Changes balance of nutrients

Question 20

Why are natural fertilisers less likely to leech?

Answer 20

N and P contained in organic molecules that need to be decomposed by microorganisms before plant uptake
- Release into soil more controlled