HL 1 Biology

5.1b Energy in Ecosystems

<<Energy Flow in Food Chains>>

  • initial source of energy for most communities: light captured by plants through photosynthesis
  • light converted to chemical energy in plants
  • some used in cellular respiration, released as waste heat to the environment
  • Energy stored in plant tissue passed on to next trophic level by primary consumers




A simple food web (p. 181)

1)  Both are top predators and occupy more than one trophic level. Both can also be predator/prey of the other. Yet the Belastoma has higher productivity.

2) The two Ranatra and Belostoma can both be considered as secondary, tertiary and quartenary consumers.

3)  (a) Metaphyton, Hyalella, Telebasis, Belostoma ( b) Telebasis

4) First rung is sum of metaphyton and epiphyton energy values and also, the first rung is labelled as producers or with species name. The Second rung is labelled primary consumers; second rung shown 5% as wide as first rung.

5) (Final-Initial)/Initial x 100% = – 95.3%

6)   Some organisms can occupy more than one trophic level at the same time, it can occupy different trophic levels at different points in their life cycle. Also, it is easier to define trophic level in a food chain rather than a food web.

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