Energy Transfer and Nutrient Cycles

Question 1

What is an ecosystem?

Answer 1

All the biotic and abiotic factors in a particular area.

Question 2

What is the glucose that isn’t used for respiration in plants used for?

Answer 2

To make up other biological molecules that make up its biomass.

Question 3

What is biomass?

Answer 3

The mass of living material or the chemical energy stored in the plant.

Question 4

How can biomass be measured?

Answer 4

By mass of carbon content or dry mass of its tissue per unit area per unit time. Carbon mass usually half of dry mass.
kg m^-2 yr^-1

Question 5

How would you measure chemical energy stored in biomass?

Answer 5

Burning biomass in calorimeter, the amount of heat given of J or kJ. Burning biomass used to heat water, the change in temperature indicative.

Question 6

What is GPP (gross primary production)?

Answer 6

Total amount of chemical energy in a plant converted from light energy in a given area at a given time.
Around 50% lost to environment as heat during respiration R (respiratory loss).

Question 7

What is NPP (net primary production)?

Answer 7

Remaining chemical energy after GPP - R. The energy available for growth and reproduction stored in biomass - available to organisms in next stage of food chain.

Question 8

What is the equation for net primary production?

Answer 8

NPP = GPP - R

Question 9

How is chemical energy lost by consumers?

Answer 9

Not all food eaten, some indigestible so comes out in faeces, lost to environment through respiration and urination.

Question 10

What is the consumers net production?

Answer 10

The energy that is left after all the loss - stored in consumers biomass.

Question 11

What is the calculation for the net production of consumers?

Answer 11

N = I - (F + R)

N - net production
I - chemical energy in ingested food
F - chemical energy lost in faeces and urine
R - chemical energy lost in respiration

Question 12

How to calculate efficiency of energy transfer.

Answer 12

Energy received / net production x 100

Question 13

How can you increase amount of energy available for consumption?

Answer 13

Reduce loss to other organisms and loss through respiration.

Question 14

To simplify a food web you need to get rid of pests, what is a pest?

Answer 14

Organisms that reduce he amount of energy available for crop growth and thus NPP - ultimately energy available to humans.

Question 15

Describe the two chemical pesticides.

Answer 15

Insecticides kill insects that eat and damage crops meaning less biomass is lost from crops letting them grow larger and increase NPP.
Herbicides kill unwanted plant species by removing direct competition for Suns energy allowing them to grow larger, more NPP - also removing habitat or food source for insect pests.

Question 16

Describe the biological agents.

Answer 16

Parasites live in or lay eggs on insects, killing them or reducing their function.
Pathogenic bacteria and viruses kill pests.
Natural predators in ecosystems.

Question 17

How can farmers reduce respiratory losses in their livestock?

Answer 17

Controlling conditions they live in so more energy used for growth, increasing NPP.
Pens with restricted movement, indoors with maintained temperature.

Question 18

What is the result of preventing respiratory losses?

Answer 18

More biomass, more chemical energy stored, increased NPP, efficient energy transfer to humans.

Question 19

What are the ethical issues of controlled livestock conditions?

Answer 19

Cause pain, distress, restricts natural behaviour.

Question 20

What is a saprobiont?

Answer 20

Decomposer, feed on dead plant and animal material by secreting enzymes to externally digest their food (extra cellular digestion) and absorb nutrients.
Organic molecules become inorganic ions - saprobiotic nutrition.

Question 21

Describe the symbiotic relationship between fungi and plant roots - mychorrhizae.

Answer 21

Fungi in longs thin str ages slows hyphae that connect to roots increasing surface area helping to increase ion and water absorption and fungi receive organic compounds in return.

Question 22

Why does rhe mirrored cycle occur?

Answer 22

Plants and animals can’t use gaseous nitrogen, needs to be converted by bacteria into nitrogen containing compounds.

Question 23

What are the four stages of the nitrogen cycle?

Answer 23

1. Nitrogen fixation
2. Ammonification
3. Nitrification
4. Denitrification

Question 24

What happens during nitrogen fixation?

Answer 24

Bacteria found in root nodules of legumes turn nitrogen into ammonia which then is turned into ammonium ions.
Mutualism if relationship where bacteria provide plant with nitrogen compounds and they receive carbohydrates.

Question 25

What happens during ammonification?

Answer 25

Nitrogen compounds from dead organisms and their urine and faeces turned into ammonia by saprobionts and then to ammonium ions.

Question 26

What happens during nitrification?

Answer 26

Ammonium ions in soil changed into nitrogen compounds, nitrates that can be used by plants. Nitrifying bacteria turn ammonium ions to nitrites then nitrifying bacteria change nitrites to nitrates.

Question 27

What happens during denitrification?

Answer 27

Nitrates in soil converted into nitrogen gas by denitrifying bacteria - nitrates in soil used to carry out respiration and produce nitrogen gas in anaerobic conditions (waterlogged soil).

Question 28

What other ways can nitrogen get into an ecosystem?

Answer 28

Lightning fixes atmospheric nitrogen.

Artificial fertilisers produced from atmospheric nitrogen.

Question 29

What is phosphorous needed for?

Answer 29

Biological molecules - phospholipids, DNA, ATP.

Question 30

How is phosphorous in rocks released?

Answer 30

Dissolves into ocean as rocks are eroded in form of phosphate ions - can be absorbed and used by plants and producers.

Question 31

Describe the phosphorous cycle.

Answer 31

Phosphate ions released from rocks into soil by weathering, taken into plants by roots with mychorrhizae increasing the rate is assimilation, transferred through food chain, lost in waste products, when they die saprobionts break down dead animals and their faeces and urine releasing phosphate ions into soils. Weathering of rocks releases ions into seas, lakes and rivers where it is taken up by aquatic producers.

Question 32

What is guano?

Answer 32

Sea bird waste product which contains high proportion of phosphate ions, adds phosphate back to soil and is often used as a natural fertiliser.

Question 33

What is the issue of harvesting crops?

Answer 33

Mineral ions taken by the plant are not returned through their decomposition - saprobionts.

Question 34

What is the issue of removing animals from land?

Answer 34

Nutrients taken from grass, moved or slaughtered elsewhere meaning the nutrient aren’t replaced through their remains or waste.

Question 35

What is the function of fertilisers?

Answer 35

Replace lost minerals so more energy from ecosystem can be used for growth increasing the efficiency of energy transfer.

Question 36

Artificial fertilisers.

Answer 36

Inorganic, contain pure chemicals.

Question 37

Natural fertilisers.

Answer 37

Organic, manure, composted vegetables, crop residue and sewage sludge.

Question 38

What is the issue of leaching?

Answer 38

If too much fertiliser applied it can leach into waterways causing euthrohoication, usually occurs following heavy rainfall. Inorganic ions soluble making them easily leach.

Question 39

Why are natural fertilisers better?

Answer 39

Nitrogen and phosphorus still in organic molecules that need to be released by decomposition so their release for uptake is more controlled and less likely to leach.

Question 40

Why is phosphate leaching less likely than nitrate leaching?

Answer 40

Phosphates are less soluble in water.

Question 41

What is another issue with fertilisers?

Answer 41

Change balance of nutrients in soil - potentially too much of one type which could cause plants and crops to die.

Question 42

Describe eutrophication.

Answer 42

Mineral ion leached from fertilised fields stimulate the rapid growth of algae in ponds and rivers which blocks light from reaching plants below eventually causing them to die as they cannot photosynthesise sufficiently. Bacteria feeds on the dead plant matter, increased bacteria reduce oxygen concentration due to aerobic respiration which causes fish and aquatic organisms to die as there isn’t enough dissolved oxygen.