Ecosystems 3 Flashcards
What is biomass?
the mass of living material present in an organism
How is biomass transfer represented?
in food chains, food webs and pyramids of biomass
biomass at trophic level =
biomass in each organism x total no. organisms in trophic level
Why are producers not 100% efficient?
not all sunlight is converted into biomass
-some light energy is reflected or transmitted through the leaf so isn’t all used for photosynthesis
-other factors limit photosynthesis
Why isn’t all the biomass transferred between trophic levels?
- not all biomass is eaten (eg, bones, roots, etc)
- energy is lost to surroundings (as metabolic heat from movement and respiration)
- some parts of food eaten are indigestible so are egested as faeces
- some energy is lost as excretory materials (eg. urine)
ecological efficiency =
biomass transferred
_________________________ x 100
biomass before transfer (intake)
What is ecological efficiency?
Biomass transfer from one trophic level to the next
How do human activities manipulate the transfer of biomass through ecosystems?
agriculture (environment is manipulated to favour crops being grown and animals being reared)
-plants and animals are provided with abiotic conditions they need (eg. water, warmth)
- competition from other species is removed (eg. using pesticides, fences to prevent predators)
- agriculture shortens food chains (only 2/3 trophic levels) so less energy is lost
What is decomposition?
chemical process where a compound is broken down into smaller molecules so that they are more usable and can be returned to the environment
What is a detritivore?
an organism that speeds up decay by feeding on detritus (dead, decaying matter) which breaks it into smaller pieces
-digest internally
- increases SA for decomposers to work on
eg. woodlice, earthworms
What is the difference between decomposers and detritivores?
- decomposers digest the dead matter externally (using enzymes) and then absorb it but detritivores digest it internally
- decomposers are fungi and bacteria but detritivores are animals
-detritivores break down the organic material into smaller pieces of organic material (increasing SA for decomposers) whereas decomposers break the organic material into inorganic material.
What is nitrogen fixation?
process where atmospheric nitrogen gas is combined with hydrogen to produce ammonia
N2 + H2 → NH3
-nitrogenase enzyme involved
How is nitrogen fixed by living organisms?
- by nitrogen fixing bacteria in root nodules
eg. Rhizobium - by nitrogen fixing bacteria in soil
eg. Azotobacter
How is nitrogen fixed by non-living processes?
- by Haber process
- by lightning
Define Sustainable resource
A renewable resource which is being economically exploited in such a way that it will not diminish or run out
