nutrient cycles

Question 1

what type of microorganisms play a vital role in nutrient cycles

Answer 1

saprobionts

(fungi and bacteria)

Question 2

what 2 things do saprobionts feed on

Answer 2

remains of dead plants and animals

animal waste (faeces and urine)

Question 3

define extracellular digestion

Answer 3

bacteria secrete enzymes that hydrolyse large organic molecules into smaller inorganic molecules

ANY BACTERIA OR FUNGI THAT CARRY OUT EXTRACELLULAR DIGESTION ON REMAINS OF ANIMALS ARE SAPRIOBIONTS AS THEY ARE CARRYING OUT SAPROBIONT NUTRITION

Question 4

describe the role of saprobionts in the nitrogen cycle

Answer 4

• use enzymes to digest proteins/DNA/RNA/urea
• to produce ammonia

Question 5

what are mycorrhizae

Answer 5

fungi that increase the surface area of a plants roots

Question 6

why is the relationship between a plant and mycorrhizae symbiotic

Answer 6

both species depend on each other

Question 7

what is the benefits of a symbiotic relationship for the plant

Answer 7

hyphae
- increased surface area of roots
- leads to increased absorption of ions (e.g: phosphorus)
- increased absorption of H2O

Question 8

what is the benefits of a symbiotic relationship for the fungi

Answer 8

• get organic compounds from plant e.g: glucose

Question 9

describe the stages to the nitrogen cycle

Answer 9

• nitrogen fixing bacteria in legume root nodules carry out nitrogen fixation which means they covert atmospheric nitrogen into ammonia
  which then dissolves in water in soil to produce ammonium ions
• saprobionts carry out ammonification so hydrolyse nitrogen compounds (RNA/DNA/proteins) in dead plants /animals or waste to produce ammonia which dissolves in water to produce ammonium
• Nitrifying bacteria carry out nitrification so convert ammonium ions to nitrites and then nitrates which can then be absorbed by the plant and used to make a/a, DNA etc…
• denitrifying bacteria then carry out denitrification in water logged soil so convert nitrates back to N2

Question 10

what conditions are needed for denitrification

Answer 10

anaerobic

• water logged soil
• very compact soil

Question 11

why can the relationship between the bacteria and the plant in nitrogen fixation be described as mutalistic

Answer 11

bacteria: produces nitrogen containing compounds

plant: provides CHO (e.g: glucose) to bacteria

Question 12

give the biological importance of phosphorus

Answer 12

found in some biological molecules (phospholipids, nucleic acids, ATP)

Question 13

explain the phosphorus cycle

Answer 13

• fertilisers increase phosphate ions in lakes, oceans, soil
• phosphate ions are converted to phosphorus in rocks by sedimentation
• phosphorus in rocks is released by weathering to produce phosphate ions
• phosphate ions in dead plants and organisms are decomposed by saprobionts to phosphate ions in soil
• deposition and sedimentation convert phosphorous in dead organisms to phosphorus in rocks
• phosphate ions in soil and water are absorbed causing phosphate ions to be in plants and algae
• feeding digestion assimilation coverts phosphate ions in plants and algae to phosphate ions in consumers
• excretion and egestion and decomposition by saprobionts convert phosphate ions in consumers into phosphate ions in oceans, soils, lakes

Question 14

Summarise the common features of all nutrient cycles

Answer 14

”- Nutrient taken up by producers as simple inorganic molecules
- Producer incorporates nutrient into complex organic molecules
- Nutrient passed on to consumers when producer is eaten
- Nutrient passed along food chain to other consumers
- When organisms die the complex molecules are broken down by saprobiontic microorganisms (decomposers) and nutrient is released in it’s original simple form to be recycled”

Question 15

Explain the roles of saprobiontic organisms in nutrient recycling

Answer 15

Saprobiontic organisms (decomposers) break down complex molecules in consumers and producers when they die and release the nutrient in its original simple to be taken up by producers