Nutrient Cycles

Question 1

What roles do saprobiants have in decomposition?

Answer 1

They release enzymes into their environment which digest dead organic matter, faces and urine extracellularly. Some of those nutrients are absorbed back into the organism and the rest is left in the environment for the uptake by plants.

Question 2

What do organisms need nitrogen for?

Answer 2

They need it to make DNA, RNA, proteins and ATP.

Question 3

Describe the nitrogen cycle.

Answer 3

1. Nitrogen Fixation= Nitrogen-fixing bacteria convert Nitrogen gas in the air into ammonia. The ammonia becomes ammonium ions in the soil.
2. Ammonification Saprobiants release enzymes that decompose nitrogen-containing compounds in dead or waste material and release ammonia. The ammonia becomes ammonium ions in the soil.
3. Nitrification Nitrifying bacteria convert ammonium ions in the soil into nitrite ions and then nitrate ions. The plants then can take up the nitrate ions through their roots.
4. Dentrification= Denitrifying bacteria convert nitrate ions back into nitrogen gas.

Question 4

What is the role of the mycorrhizae in the uptake of water and ions by the roots?

Answer 4

They contain long filaments called hyphae that attach to the roots of plants. They increase the surface area of plants for the uptake of water via osmosis and inorganic ions. In return, they gain important biological molecules like glucose.

Question 5

What do organisms need phosphate for?

Answer 5

They need it to make DNA, RNA and ATP.

Question 6

Describe the phosphate nutrient cycle.

Answer 6

1. Phosphate ions are released into the ocean from the weathering and erosion of rocks.
2. Alage in the ocean takes in dissolved phosphate ions to make ATP, DNA or RNA.
3. Birds eat the algae and release guano back onto the land.
4. Saprobiants release enzymes into the soil that digest phosphate-containing compounds in dead or waste material and release the phosphate back into the soil.
5. Phosphate is taken up by the roots of the plants with the help of the mycorrhizae.

Question 7

What are fertilisers used for and why?

Answer 7

The removal of crops from the land removes nutrients from the soil and fertilisers are used to replace them.

Question 8

What are natural fertilisers?

Answer 8

They contain organic compounds from things like manure or composted vegetable waste.

Question 9

What are artificial fertilisers?

Answer 9

They contain inorganic chemicals.

Question 10

How does the leaching of mineral ions from fertilisers into the water cause eutrophication?

Answer 10

1. The leaching of mineral ions into water bodies causes an algae bloom.
2. The plants underneath the algae bloom do not receive any light, so they can’t photosynthesise. These plants die.
3. The bacteria have more food meaning they grow more quickly.
4. The bacteria take in more and more oxygen for aerobic respiration.
5. This means aquatic animals have less oxygen for aerobic respiration and die.