3.5.4 nutrient cycle

Question 1

what are saprobionts?

Answer 1

organisms that feed by extracellular secretion of digestive enzymes into external materials, hydrolysing bond forming monomers, which they can absorb.

Question 2

what do saprobionts do with excess monomers?

Answer 2

excess monomers are broken down releasing mineral ions.
amino acids > ammonia/ammonium + sugar

Question 3

nitrogen gas to ammonium/ammonia:

Answer 3

nitrogen fixation by nitrogen fixing bacteria.

Question 4

where can nitrogen fixing bacteria be found?

Answer 4

in the soil or in legumes (in their root nodules).

Question 5

ammonium/ammonia to nitrates:

Answer 5

nitrification by nitrifying bacteria.

Question 6

what are the two steps of nitrification?

Answer 6

nitrites to nitrates

Question 7

what conditions are needed for nitrification?

Answer 7

well aired soil with high oxygen concentrations.

Question 8

nitrates to nitrogen in atmosphere:

Answer 8

denitrification by denitrifying bacteria.

Question 9

what conditions are needed for denitrification?

Answer 9

water logged soil in low oxygen concentrations.

Question 10

nitrates/ammonium/ammonia to plants:

Answer 10

assimilation

Question 11

plants to animals:

Answer 11

feeding, digestion and absorption.

Question 12

animals/plants to ammonium/ammonia:

Answer 12

deamination by saprobionts.

Question 13

what type of relationship do roots of a plant and mycorrhizae have?

Answer 13

mutualistic relationship

Question 14

how do plant roots and mycorrhizae have a mutualistic relationship?

Answer 14

• mycorrhizae have long, thin filaments known as hyphae, which are connected to the plant roots.
• hyphae increase surface area of root systems of plant, increasing absorption of water and mineral ions.
• in return fungi receives carbon compounds such as carbohydrates from the plant.

Question 15

phosphate ions in oceans/soil to phosphate ions in plants:

Answer 15

absorption

Question 16

phosphate ions in plants to phosphate ions in animals:

Answer 16

feeding

Question 17

phosphate ions in animals to phosphate ions in oceans/soil:

Answer 17

excretion

Question 18

phosphate ions in animals to phosphate ions from waste and remains:

Answer 18

excretion and decomposition

Question 19

phosphate ions from waste and remains to phosphate ions in oceans/soils:

Answer 19

decomposition by saprobionts

Question 20

phosphate ions from waste and remains to phosphate in rocks:

Answer 20

deposition

Question 21

phosphate ions in rocks to phosphate ions in oceans/soil:

Answer 21

erosion and weathering

Question 22

phosphate ions in oceans/soils to phosphate ions in rocks:

Answer 22

sedimentation

Question 23

what is guano?

Answer 23

produced by birds in excretion, rich in phosphorus.

Question 24

why do farmers add mineral ions to soil?

Answer 24

• as crop harvests removes mineral ions, which results in a low concentration of minerals in the soil.
• minerals are needed in biosynthesis: amino acids and nucleic acids.

Question 25

what are artificial fertilisers?

Answer 25

consists of inorganic compounds such as ammonia nitrate.

Question 26

what are natural fertilisers?

Answer 26

consists of organic materials, such as manure, compost and sewage sludge.

Question 27

what are some of the benefits to artificial fertilisers?

Answer 27

- fertiliser is easy to store and clean to handle. - can be left for long periods (if lest in moisture proof conditions). - buy tailored fertilisers. - soluble and contains only mineral ions so fast acting.

Question 28

what are some of the benefits of natural fertilisers?

Answer 28

- have a longer lasting affected as saprobionts need to break down fertiliser into mineral ions. - cheap. - organic matter is good for soil structure and water holding capacity by binding the soil particles together. - acts a food resources for soil organisms. - recycles organic waste.

Question 29

what are some disadvantages of artificial fertilisers?

Answer 29

- expensive so farmers use sparingly, balancing increased yield benefit with cost of buying and applying fertiliser. - requires specialistic equipment for applying. - leaching.

Question 30

what are some disadvantages of natural fertilisers?

Answer 30

- difficult to match the nutrient needs of crops as nutrients depend on animal species and diet. - bulky and difficult to store. - heavy machinery needed to handle manure and difficult to apply evenly over a field. - may carry diseases.

Question 31

what knock on effect can fertilisers have on biodiversity?

Answer 31

1. fertilisers promote the growth of a certain species, which results in others being out competed for resources such as light etc. 2. fewer plant species. 3. less varied in food sources. 4. fewer niches. 5. fewer habitats. 6. fewer insect species. etc reduces species diversity and reduces BIODIVERSITY

Question 32

what is leaching?

Answer 32

when the soluble ions in fertilisers wash out of the soil when it rains, flowing into the ground water.

Question 33

what are the steps of eutrophication?

Answer 33

1. population sizes and growth rates are often limited due to a lack of nitrates and phosphate. 2. when fertiliser and ions are added it results in rapid population growths specifically in algae. 3. algae will cover the surface of the water. 4. algae will block sunlight from reaching aquatic plants below the surface of the water. 5. plants cannot photosynthesise so they die. 6. dead plant matter will increase the food supply for saprobionts such as aerobically respiring bacteria, which will have a rapid population growth. 7. decomposers will use up dissolved oxygen in the water, which will decrease oxygen concentrations. 8. creating anaerobic conditions, causing deaths in aerobically respiring animals/fish.