Flashcards in 4. Food Chains and Energy Pyramids Deck (13):
What does each species in a food chain feed on? Are there any exceptions?
- each species feeds on the previous one
- the exception is the producer, which makes its own food by photosynthesis
What is the trophic level of an organism?
its position in the food chain
Give some examples of trophic levels?
producer, primary consumer, tertiary consumer = different trophic levels
How many trophic levels does a food chain usually have?
- commonly: 3 or 4
- rarely: 5+
How can the limited length of food chains be explained?
by the theories of energy flow and energy loss:
- only a small proportion of biomass is passed from one trophic level to the next
- this proportion (expressed as %) is variable, but is unlikely to be more than 10%
- once the fourth/fifth trophic level is reached, too little energy remains to sustain another level
What do energy pyramids show?
how much energy flows through each trophic level in a community
- they clearly demonstrate the amount of energy dropped along food chains
How is energy shown in an energy pyramid?
amount of energy per square meter of area occupied by the community and per year (kJm^-2 year^-1)
What shape are energy pyramids? Are they always this shape? Why are they this shape?
- pyramid shaped
- because energy is lost at each trophic level, so less remains for the next level
Energy is lost at each successive stage of an energy pyramid. What is also lost? What does this mean?
- means that the energy content per gram of tissues of each successive tropic level is not lower
How is biomass lost?
- when carbon compounds are broken down by cell respiration and the carbon dioxide produced is excreted
- removal of waste products of metabolism such as urea
What type of graph is a pyramid of energy?
a bar chart with horizontal bars arrange symmetrically
How should you draw an pyramid of energy?
- bars drawn to scale and arrange symmetrically in horizontal position
- labels should indicate trophic level with producers at the base
- helpful to put energy values alongside each bar on pyramid