Energy and ecosystems Flashcards
Define trophic level
The position an organism occurs within an energy transfer/ feeding relationship
What are producers called and what does it mean?
Produces are autotrophic.
“Self-nourishing” - They build up complex organic compounds from simple inorganic molecules.
What are consumers called and what does it mean?
Consumers are heterotrophic
They rely on an external source of complex organic compounds (take in)
What do the arrows in a food chain represent?
The direction of transfer of energy from one trophic level to the next trophic level in the food chain
What is an organism that depends on other organisms for energy / complex organic compounds?
Heterotrophic
An organism that eats only producers is called?
Primary consumer (heterotroph)
What are saprobionts?
Secrete extra-cellular enzymes which hydrolyse organic material outside the organism = these micro-organisms then absorb the hydrolysed (smaller & soluble) monomer molecules across their cell membranes.
They break down complex organic compounds (DNA, polypeptides) in dead organisms.
Bacteria and fungi are Saprobionts / decomposers
Define Biomass
- Mass of carbon (organic compounds)
- Dry mass of tissue per given area
Suggest what you should do to ensure all water is removed from a tissue / sample.
- Regularly weigh and Heat (less than 100 °C)
- Until mass is constant
What is Gross Primary Productivity
Rate of conversion of light energy into chemical energy (by producers)
What is Net Primary Production
- Chemical energy store in plant biomass after respiratory losses to the environment have been taken into account. NPP= GPP -R
- NPP is available for new plant growth and reproduction OR available for other trophic levels in the ecosystem, such as herbivores and saprobionts.
- kJ ha–1 year–1 OR kJ km–2 year–1 OR kJ km–3 year–1
The percentage of the light energy trapped by the producers is very low. Give two reasons why.
- Reflected / absorbed by water vapour;
- Reflected from producers / wrong wavelength;
- Transmitted / passes between chloroplasts/ between plants / too few chloroplasts;
The biomass of primary consumers is less than the biomass of producers. Explain why.
- Loss of energy/heat / use of energy / less energy to be passed on;
- In respiration;
- In excreta / excretion / urine / carbon dioxide;
- Inedible parts / indigestible parts / egesta / egestion / to decomposers;
An ecosystem rarely supports more than 5 trophic levels. Why?
Some energy is released at each trophic level
Because energy is lost between each trophic level, very little energy remains at level 5
What is Photosynthetic efficiency
Its a measure of the ability of a plant to absorb light energy and convert this light energy into chemical energy. It depends on external factors such as light intensity and temperature.
