Energy and Ecosystems Flashcards
Define Population
all the organisms of one species in a habitat
Define community
all the different organisms of all species living in a habitat at a particular time
Define habitat
the place where an organism lives
Define niche
the role of a species in an ecosystem
Define trophic level
a stage of the food chain
What is productivity
the amount of energy transferred between trophic levels
What is gross primary production
The total amount of energy made by a producer KJm-2yr-2
What is respiratory loss
energy used in respiration
What is nett primary production
The amount of chemical energy the producer stores as biomass
How do we calculate net production?
N = I (R+F) where I is total energy ingested
R is respiratory loss, and F is energy lost via faeces/urine
Why is the efficiency of energy transfer between the sun and a plant very low? (approx. 2%)
- wrong WL of light
- light hits non photosynthetic region eg) bark
- light reflected
- lost as heat
Why is the efficiency of energy transfer between the plant and a consumer low? (approx. 10%)
- respiratory loss
- lost as heat
- not all plant is eaten
- some not digested
Why is the efficiency of energy transfer between the consumer and a secondary consumer low? (approx. 10 -15%)
- respiratory loss
- primary consumer uses energy for metabolism
- not all is eaten
- faeces
- lost as heat
Why might energy transfer be low?
- old animal - less energy into biomass
- herbivores - more faeces
- homiotherms/ endotherms (warm blooded)
How can farmers increase energy transfer efficiency within plant crops?
- reduce competition (herbicide/ insecticide)
- fertilisers - eg) nitrates
How can a farmer increase yield with animals?
- restrict movement - reduce respiratory loss
- keep warm
- slaughter the animal whilst it is still young
- control diet so a higher % of food is digested
what technique to increase yield can be applied to both animals and plants?
selective breeding
How can we measure an organisms dry biomass?
warm sample on a scale until mass remains constant (water has been removed)
when measuring biomass why is the temperature kept below 80 degrees Celsius?
to avoid combustion CO2 = biomass
Why do we use dry biomass to compare samples?
amount of water varies eg) cucumber and potato
dry biomass is more representative
What are the units for biomass?
Kgm-2
How else can we compare organisms?
mass of carbon
What are the units for mass of carbon?
kgm-2yr-1
Why don’t we use mass of carbon as much as dry biomass?
hard to measure
How can we use calorimetry to estimate the energy stored in dried biomass?
burn substance completely
to heat a known volume of water
measure the temperature change and calculate the energy released
describe the 6 stages of the nitrogen cycle
1) Ammonium ions —> nitr1tes by nitrification
2) nitrites —–> nitrate (late) by nitrification
3) denitrification in anaerobic conditions to nitrogen gas in atmosphere (unreactive)
4) nitrates to plants or nitrogen fixation of nitrogen in the atmosphere by leguminous plants
5) saprobiotic nutrition of animals and plants by decomposers
6) Ammonification of decomposer = back at 1
what are the 2 ways phosphate ions are returned to the soil in the phosphorous cycle?
weathering and erosion of rocks
saprobiotic nutrition
What is the role of microorganisms in the recycling of nutrients?
break down large organic compounds into small inorganic compounds (often soluble so they can be absorbed by plants)
What is a saprobiont?
digests food using extracellular enzymes by saprobiotic nutrition
Define Saprobiotic nutrition
digestion of organic matter by extracellular enzymes
What are Mycorrizhae?
fungi that grow in a mutualistic relationship with plant roots
how do plants benefit from the mycorrhizae?
increased SA of roots increases absorbtion of water and minerals
how do mycorrhizae benefit from the relationship with plants?
exchange of organic substances eg) sucrose
What is a natural fertiliser?
contain nitrogen and phosphorous in organic compounds eg)compost
What are the disadvantages of natural fertilisers?
still need to be broken down by saprobionts so slower release of phosphate ions and nitrates
what are the advantages of natural fertilisers?
aerates soil - decreases anaerobic denitrification
wider range of elements
less leaching
uses less energy
what is the impact of farming/use of fertiliser?
removes N and P from cycle so soil becomes depleted
fertiliser is added
too much fertiliser can alter the water potential (more negative) making it harder for the plants to absorb water by osmosis
what is artificial fertiliser?
inorganic chemical compounds that contain nitrogen and phosphorous
what is leaching?
when soluble compounds are washed off the land by rain - more common in artificial fertilisers as they are soluble
Describe the 7 steps of eutrophication
1) nitrates/ phosphate ions are leached into fresh water
2) Algal bloom
3) blocks out light
4) plants below surface cannot photosynthesise so die
5) saprobionts break down dead plants
6) saprobionts respire anaerobically and use up O2
7) fish and other organisms die
