Energy Flow
Biology: IB Diploma Higher Level, topic 8.2.2
Energy Flow
All energy in biological systems comes first from the Sun. The full route taken is described below:
Light energy from the Sun
Chemical energy in plants
Chemical energy in animals
Energy in decomposing matter
Food Chains
Food chains show the feeding relationships and transfers of energy within a community. Food webs show networks of interconnected food chains. Below are some important food chain definitions:
Trophic levels
- Each organism in a food chain occupies what is called a trophic level.
- Depending on their role as producers or consumers, species or groups of species can be assigned to various trophic levels.
Producer
- A primary producer is an organism that makes its own organic nutrients, usually using energy from sunlight.
- A decreased level of sunlight can impact the number of producers at the base of a food chain.
- This, in turn, can reduce the number of trophic levels and number of consumers at subsequent trophic levels.
Consumer
- A consumer is an organism that gets its energy by feeding on other organisms.
- Depending on the position of the consumer in the food chain, it may be classed as primary, secondary or tertiary.
- Higher-level consumers feed on the next lower tropic levels, and so on, up to the organisms at the top of the food chain: the apex consumers
Food chain
Energy loss
- One major factor that limits the length of food chains is energy.
- Energy is lost as heat between each trophic level due to the second law of thermodynamics.
- Thus, after a limited number of trophic energy transfers, the amount of energy remaining in the food chain may not be great enough to support viable populations at yet a higher trophic level.
Food webs
- There is a problem when using food chains to accurately describe most ecosystems.
- Even when all organisms are grouped into appropriate trophic levels, some of these organisms can feed on species from more than one trophic level.
- Likewise, some of these organisms can be eaten by species from multiple trophic levels.
- A holistic model which accounts for all the interactions between different species is a more accurate a model for ecosystems.
- To do this we can draw a food web.
Food webs
Test yourself on Energy Flow
Energy Flow in Biological Systems
Energy flow in biological systems
Name the first four components of a typical food chain
Producers make their own food using light energy from the sun. What is this process called?