Topic 5B - Energy Transfer and Nutrient Cycles

Question 1

Importance of nutrient recycling

Answer 1

Finite resources, recycle to not deplete as plants etc need them for growth and function - this is why organisms decompose to not lock up nutrient

Question 2

3 nutrient cycles

Answer 2

nitrogen, carbon, phosphorus

Question 3

see samsung notes for carbon cycle

Answer 3

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Question 4

In a rainforest, explain how Co2 conc. changes over both the day and at different heights (use photosynth. and respiration).

5 marks

Answer 4

• increase CO2 at night, no photosynthesis & all respiration
• more CO2 released linked w/ resp. at night
• in light more uptake of CO2 and increased rate of photosynthesis compared to resp.
• ground level : less photosyn. and more microbes resp.

Question 5

exam Q booklet for carbon cycle

Answer 5

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Question 6

What term to use at a level instead of decomposers

Answer 6

Saprobiont (saprobiotic nutrition), decomposers as they respire -
use carbon compounds from decay in resp.

Question 7

3 things a saprobiont does.
- important extra note *

Answer 7

1. Feed /digest remains of dead, and waste material - breaks them down. Name specific compounds broken down, maybe where they maybe found :
   - carbs: breaks glycosodic bonds
   - proteins: into amino a., peptide band
   - lipid: glycerol & fatty acid, ester
2. Extracellular digestion, enzymes secreted and food digested externally and absorbed. Humans have internal environment for this.
3. Breaks down organic molecules into inorganic ions (no carbon in them)
   * Fungi like mycorrhizae do saprobiotic nutrition through decomposing and can make nitrates in decaying matter much more quickly available

Question 8

Some fungi,mycorrhizae, form a symbiotic (close association) relationship with plant roots.

What type of symbiotic relationship is it? What does each party do?

Answer 8

mutualistic - you can look the rest up.
My corrhizal fungi increase SA of roots using hyphae to ^ uptake of water & mineral ions.
Plant let fungi access phloem and get organic groups like sucrose (less reactive for plants than glucose) from photosynthesis and amino acids - allows resp. to release energy and fungi can grow

Question 9

what are the lang thin strands that mycorrhizae use to connect to roots called?

Answer 9

hyphae

Question 11

mycorrizhae

Answer 11

very common relationship between fungi and plant roots

Question 12

abiotic factors affecting survival of mycorrhizae

Answer 12

Moisture, temp, oxygen availability, photosynthesis levels of plant etc

Question 13

What human activity kills mycorrhizae?

Answer 13

Pollution, soil erosion, and land use (soil distribution) can kill them

Question 14

How does mycorrhizae benefit the community

Answer 14

Can make plant grow faster as they receive the nutrients first, and they can transfer organic compounds between plants, and can protect plant from pathogens

Question 15

How do plants absorb nitrogen?
Where is nitrogen used in plants and animals?

Answer 15

By actively transporting it through roots. It’s used in making DNA (nucleic acids), amino a., proteins like enzymes and antibodies, ATP

Question 16

Difference between nitrites and nitrates?

Answer 16

Nitrates are formed from nitrites when an oxygen molecule is added.

Question 17

Difference between ammonia and ammonium ions

Answer 17

Ammonia has one less hydrogen atom so isn’t charged (mentioned please frequently)

Question 18

Watch recap vids on nitrogen cycle

Answer 18

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Question 19

Nitrogen cycle on drawn notes

Answer 19

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Question 20

nitrogen fixation and microbe involved.

Answer 20

Aerobic resp.

Nitrogen - fixing bacteria living free in soil or root nodules (these have air pockets with nitrogen) of leguminous plants.
Nitrogen gas is (oxidised?) converted into ammonia, dissolving in water to make ammonium ions in the soil.

Question 21

Why would farmers use crop rotation with legumes?

Answer 21

Root nodules w/ nitrogen - fixing bac. fertilise soil w/ ammonium ions…. eventually into nitrates available for plant to absorb by active transport.
Soil in farming is usually infertile due to no crops dying, no decomposing - no nutrients recycled

Question 22

Ammonification and microbes involved.

Answer 22

Aerobic resp.

Dead biomass and waste / urine allow for the proteins / DNA (nitrogen compounds) in them to be released when decomposed by saprobionts.
Ammonium ions formed.

Question 23

What can farmers add to soil to replace crops that cannot be
left to decompose?

Answer 23

Fertiliser, natural - manure/ urine, or artificial

Question 24

Nitrification and microbe involved.

Answer 24

Aerobic resp.

OXIDATION of ammonium ions into nitrites and also then nitrates by nitrifying bacteria.
- farmers want to ensure maximum oxygen in soil for this (see farming techinques)

Question 25

Which bacteria in the nitrogen cycle aerobically respire and which do anaerobically?

Answer 25

Denitrifying bac, anaerobically. All other bac aerobic resp.

Question 26

Denitrification and microbe involved

Answer 26

Only anaerobic resp process! Denitrifying bacteria thrive in low oxygen soil levels and convert nitrates in the soil back into nitrogen gas. - farmers don't want nutrients being converted back into the atmosphere, so they will have methods to ensure aerated soil as much as possible to increase growth.

Question 27

Benefits of ploughing to farmers

Answer 27

Aerates soil: promotes aerobic bacteria (mention) and limits anaerobic denitrifying. You dig and mix up soil, may add organic matter

Question 28

Benefits of crop rotation (normal plants)

Answer 28

Helps increase microbial diversity In soil AND rotating every year or so plants that require different nutrients / bac so soil isn't stripped of specific ones.

Question 29

Benefits of crop rotation (legume)

Answer 29

Planting legumes for a period of time = nitrogen fixing bacteria in nodules increases the rate of nutrients replenishing, specifically ammonia > ammonium compounds/ ions.... then nitrites > nitrates, so soil isn't barren. - can mix them in with other crops so not all same nutrients / ions absorbed : allows soil ion concentrations to recover AND improve fertility.

Question 30

Benefits of fallow land to farmers

Answer 30

Where previous dead vegetation allowed to die & decompose (natural process of allowing any plants to grow and die). Restores nitrogen levels as saprobionts decompose them and carry out ammonification from DNA/ proteins in matter into ammonia and then ammonia compounds / ions. - allows different levels of ions to accumulate for next year's crops

Question 31

Benefits of draining water-logged fields to farmers

Answer 31

Ensures that water levels aren't limiting the oxygen levels in the soil, so increases O2... link to bacteria - keeps soil fertile (either due to point above, or nitrates not being dissolved and washed away) ! Ensures less denitrifying bacteria in soil (as waterlogged soil isn't aerated)... STATE what these bacteria do and how it means less nitrates for plant growth

Question 32

assimilated

Answer 32

taken in (by plants)

Question 33

Uncultivated land

Answer 33

Likely to have legumes growing, so high rate of nitrogen fixation and fertile soil

Question 34

suggest how nitrogen cycle may have been altered by human activity

Answer 34

Fertilisers = more nitrates available to plants ( increased nitrate conc. overall)

Question 35

What is phosphorus used in animals and plants?

Answer 35

DNA, any nucleic acids, phospholipid bilayer, ATP

Question 36

main sources of phosphorus in the world?

Answer 36

Rocks and also in oceans when rocks dissolved / weathered

Question 37

in what form is phosphorus found?

Answer 37

organic phosphate in rocks and when dissolved in ocean, phosphate ions made

Question 38

How does phosphorus get into the food chain?

Answer 38

When phosphate ions dissolve in water, it's absorbed by soil and assimilated by plants

Question 39

Guano

Answer 39

The name for large amours of sea bird excrement, v. common coastal areas. It can be used as a natural fertiliser as it contains high conc. of phosphate ions to return the large amounts to the soil

Question 40

2 ways phosphate ions are returned from organisms to soil

Answer 40

Waste products and decomposition/ death - via ammonification, saprobionts by extracellular digestion, breakdown DNA / ATP, etc, in the waste

Question 41

2 types of saprobionts

Answer 41

Bacteria and fungi

Question 42

How saprobionts digest their food? And how does this benefit phosphorus cycle?

Answer 42

Extracellular digestion of dead biomass containing phosphorus, using digestive enzymes, in soil, and absorb it. They then release P ions into soil for plant assimilation

Question 43

Why fertilisers are used

Answer 43

To increase yield and make plants grow to max (add biomass), increase crop productivity - they need to add these as harvesting means little decomposition to return / recycling nutrients to soil

Question 44

3 chemicals of artificial fertilisers

Answer 44

NPK is common Nitrogen Potassium Phosphorus - at diff concentrations

Question 46

2 types of fertilisers used; how soluble is each and what form?

Answer 46

Organic fertilisers: animal excretion and urine or even food waste (as sludge, sewage, compost etc) > not as soluble Inorganic: NPK/ pure chemicals as pellets or powders > making them very soluble.

Question 47

What is the cause of eutrophication?

Answer 47

Leaching: Soluble compounds washed out of soil by the rain/irrigation systems (e.g. spraying water on plants) carrying nearby streams, ponds. The Leaching of extra fertilisers causes eutrophication via build up of nitrates and phosphates in areas of water

Question 48

How mineral ions are lost from crop field?

Answer 48

Idea of constant harvesting, no recycling via saprobionts etc

Question 49

Explain eutrophication

Answer 49

1. Leaching of excess ions, like... stimulates growth of uni cellular algae population in pond or river 2. Large amounts of algae block light from reaching plants below, some start to die 3. Death as can't photosynthesis enough 4. Saprobiont feed on dead plant matter, ^ numbers of bac respiring aerobically reduce oxygen concentration in water = ANOXIC water conditions 5. Fish and animals die as not enough dissolved oxygen to respire aerobically

Question 50

Factors caused by humans for eutrophication

Answer 50

Pollution (factories) , runoff from construction or street, discharge of untreated sewage

Question 51

Signs of eutrophication

Answer 51

Dead fish on water, algal boom

Question 52

Why eutrophication less likely in fast stream?

Answer 52

- algae move and don't block light, nutrients leached keep moving so can't accumulate to algal bloom, and oxygen being reintroduced more - fish can move to waters with higher oxygen

Question 53

Why should organic fertilisers be used now?

Answer 53

Less soluble than inorganic and so less likely to leach, also because of lower concentrations of each chemical. Phosphate and nitrates need to be released from decomposition by saprobionts first for plants to absorb

Question 54

Note

Answer 54

Phosphates are less soluble than nitrates