Topic 5B: Energy Transfer and Nutrient Cycles Flashcards
1
Q
What are biotic factors?
Give an example
A
- Living
e.g. predators, food availability, pathogens
2
Q
What are abiotic factors?
Give an example
A
- Non-living
e.g. temperature, light availability, water availability, pH, salinity
3
Q
Define ecosystem
A
- All organisms and the biotic & abiotic factors in an area
4
Q
Define population
A
- All organisms of one species in a habitat
5
Q
Define community
A
- All organisms of all species in a habitat
6
Q
Define habitat
A
- The place an organism lives
7
Q
Define niche
A
- The role of a species in an ecosystem
8
Q
Define trophic level
A
- Each stage of a food chain
9
Q
What productivity values do plants have?
A
- GPP -> total amount of energy made by a producer (units = given area per unit time - kJ/m^2/yr)
- NPP -> biomass accumulated
- R -> respiratory losses
10
Q
How is NPP calculated?
A
NPP = GPP - R
11
Q
What productivity values to animals have?
A
- I -> total energy ingested
- R -> respiratory losses
- F -> faeces and urine
- N -> net productivity
12
Q
How is net productivity (N) calculated?
A
N = I - (R + F)
13
Q
How do you calculate energy transfer efficiency?
A
- N/I x100
14
Q
How is energy lost from the sun to a producer?
A
- Light reflected
- Not all light shines on photosynthetic areas
15
Q
How is energy lost between producers and primary consumers?
A
- Respiration
- Heat
- Not all of the producer eaten - e.g. deep roots
- Some not digested - e.g. cellulose
16
Q
How is energy lost between consumers?
A
- Respiration, heat
- Not all eaten - e.g. bones
17
Q
How do you make dry biomass?
A
- Put in an oven on a low temperature - prevent combustion
- Regularly measure the mass
- When the mass remains constant - all the water has been removed - now dry
18
Q
What unit do you measure dry biomass in?
A
kg/m^2
19
Q
Describe calorimetry
A
- Estimates the amount of energy stored in dry biomass
- Burn a sample of dry biomass completely to heat a known volume of water
- Change in temperature is used to calculate the chemical energy of the dry biomass
20
Q
What is mass of carbon?
A
- Organisms are made of organic compounds that contain carbon
- Mass of carbon is a good biomass indicator
- Very difficult to measure
- Mass of carbon is around 50% of dry biomass
- Measured in kg/m^2/yr - accounts for seasonal changes
21
Q
What are the two types of decomposers?
A
- Saprobiotic microorganisms -> extracellular digestion - secrete enzymes to hydrolyse molecules - then absorb the smaller molecules produced (fungi, bacteria etc)
- Detritivores -> feed on dead / decaying matter, digest in the body (earthworms, maggots etc)
22
Q
In farming what are 2 methods of reducing lost energy?
A
- reducing energy lost to other organisms
- reducing energy lost through respiration
23
Q
What are ways of simplifying food webs?
A
Chemical pesticides
- Insecticides -> kill pests, less biomass lost, grow more, inc NPP
- Herbicides -> kill weeds, removes direct competition, removes pest food sources
Biological agents
- Parasites -> Kill insect / reduces its function, live or lay eggs on pest, viruses / bacteria - kill pests
24
Q
How are these methods of simplifying food webs best used?
A
- As integrated systems
- Use both chemical and biological
- Reduces pest numbers further than one method alone
- Even more inc in NPP
25
What are ways of reducing respiratory losses?
Controlling conditions
- Restrict movement -> Small pens, indoors, warm
- Less energy wasted on maintaining body temperature
- More biomass produced, inc NP and energy transfer efficiency
26
What are the benefits of reducing respiratory losses?
- More food produced in less time
- Lower cost
27
What are issues with methods of reducing respiratory losses?
- Ethics
- Pain, distress caused
- Restricts the natural behaviour of animals
28
Why are fertilisers needed?
- Crops take in minerals from soil as they grow
- When they are harvested these are taken with them
- They do not die and decompose there - nutrients not recycled back in by decomposers
- Nutrients also lost as animals eat plants and are then moved away
29
What do fertilisers do?
- Replace lost minerals and increase energy efficiency
30
What are artificial fertilisers?
- Inorganic
- Pure chemicals
- Powders / pellets
31
What are natural fertilisers?
- Organic matter
- Manure, composted vegetables, crop residue, sewage sludge
32
What are issues with fertilisers?
- Too much applied - overflow leaches into waterways
- Happens when fertiliser applied before heavy rainfall
- Change the nutrient balance of the soil - can cause crop death
33
How do natural fertilisers have less issues?
- Minerals are contained in organic molecules
- They need to be decomposed first
- Cause a more controlled release - less likely to leach away
34
What nutrients are less likely to leach?
- Phosphates
- Less soluble
35
What causes eutrophication?
- Excess nutrients
36
Describe the process of eutrophication
1. Mineral ions from fields cause rapid algal growth
2. Algae blocks sunlight from reaching plants below
3. Plants die as they cannot photosynthesise
4. Bacteria feed on dead plants - aerobically respire reducing O2 concentration
5. Fish & aquatic organisms die - not enough dissolved O2
37
How do fungi help plants?
- Form symbiotic relationships with plant roots - mycorrhizae
- Long, thin strands (hyphae) - inc SA to absorb ions and water
- Fungi gain compounds such as glucose from the plant
38
Describe the nitrogen cycle
nitrification nitrification denitrification
[Ammonium ions] ---->> [nitrites] ---->> nitrate ---->> N2 in air
^ feeding l absorption l
l (animals)<<----- (plants)<<----------
l death & excretion l l death nitrogen
--------------------------------(decomposers) fixation
ammonification
39
What things contain nitrogen compounds?
- Proteins
- DNA
40
What is nitrification?
- Ammonium ions to nitrogen compounds for plants - oxygen added
- Done by nitrifying bacteria
41
What is denitrification?
- Nitrates in the soil are converted to nitrogen gas
- Done by bacteria
- In anaerobic conditions only --> aerate soil, not waterlogged
42
What is nitrogen fixation?
- Nitrogen from the atmosphere turned to nitrogen containing compounds
- Done by bacteria in the root nodules of leguminous plants
- N2 -> ammonia -> ammonium ions
- Form a mutualistic relationship
43
What is ammonification?
- Saprobionts turn nitrogen compounds from dead organisms into ammonia
- Also done to animal waste
44
Describe the phosphorus cycle
(fish)---->>(birds) (plants)----------->>(animals)
l l / \ / \
(algae) [guano]---->>[soil]<<--(decomposers)<<--[urine&]
l ^ [faeces]
[seas&] l
[lakes] <<------------------- [rock]
45
What things contain phosphates?
- DNA
- ATP
- Phospholipids
46
How are phosphates released from rocks?
- Weathering releases phosphates from rock to soil and bodies of water
47
How do plants obtain phosphates?
- Absorb them through the roots from the soil
48
How do phosphates travel from the sea to the soil again?
- Phosphates taken in by aquatic producers
- Passed along the food chain to fish and then sea birds
- Waste from sea birds - guano - high proportion of phosphates which are returned to the soil
- Often used as a natural fertiliser
