Chapter 13 - Energy and Ecosystems Flashcards
What is the basis of all ecosystems and why
Plants or other photosynthetic organisms as they are the primary producers for the food chain
Why does biomass decrease from primary producers to primary consumer?
Becuase a lot the sugars produced from photosynthesis are used as respiratory substrates, with only a small amount becoming plant biomass
What is biomass and how can it be measured?
The biomass of an organism is the amount of material it contains dry, and can be measured as dry mass of tissue or dry mass of carbon per area. The energy store of the biomass can be determined through calorimetry.
What is Gross Primary Production?
GPP is the total amount of chemical energy stored in all of the plant biomass in a given area
What is Net Primary Production? Can you give its formula?
NPP is the chemical store of energy in a given area after respiratory losses have been considered (NPP = GPP - R (respiratory loss)
What is NPP used for in ecosystems?
NPP can be used for plant growth and reproduction, as well as being available to other trophic levels in the system, such as primary consumers and decomposers.
What is the net production of consumers?
It is N (net production) = I (ingested food) - (F (excretory losses) + R (respiratory losses)
How do farming practices increase the efficiency of energy transfer?
Reducing the amount of biomass lost to non-human food chains (insects for example)
Trying to reduce respiratory losses within human food chains
What are the 2 major type of nutrient cycles within natural ecosystems?
Phosphorous and nitrogen
Describe the involvement of bacteria in the nitrogen cycle:
Saprobionts in the soil break down proteins and amino acids from decaying organisms into ammonium in the soil, which can be nitrified by nitrifying bacteria (niter somonas and niter bacter) into nitrites and then nitrates, usable by plants.
Why are nutrients lost from systems and what can be done to replace them?
Ususally small amounts of nutrients are lost by runoff, or in anaerobic conditions denitrfying bacteria will turn nitrates into atmospheric nitrogen. Furthermore however, farming practices don’t let plants breakdown or be excreted back into the ecosystem causing a massive loss in biomass and nutrients, so fertilisers must be used.
Pros and cons of artificial vs natural fertilisers?
Natural fertilisers are good for the soil and contain differing levels of lots of nutrients and therefore help a wider variety of plant species, encouraging biodiversity, however this makes it bad for intense farming practices because it does not create the optimum conditions for the one grown crop.
Artificial fertilisers on the other hand are usually specific to each crop and therefore only encourage their growth, reducing biodiversity and they often use chemicals which is bad for the soil.
Give an example of a negative result of heavy fertiliser use
Nutrient runoff can cause nitrates to enter rivers and ponds leading to eutrophification. This is where the fertilisers allow algae to grow quickly on the surface, preventing light from reaching the bed, preventing photosynthesis resulting in the plants using up oxygen in the water and then dying. When they die saprobionts break them down in an aerobic process, further lowering oxygen in the pond until other aquatic organisms suffocate, at which point the saprobionts will break them down anaerobically, releasing hydrogen sulfide (rotten egg smell)
