Food & Energy: Energy Transfer & Ecosystems

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All organisms need energy to survive, some get of these organisms get their energy from sun (like plants with photosynthesis) and others are able to get their energy from consuming other organisms. Organisms living in a particular area and any non-living conditions within the area are together treated as an ecosystem.

Food Chain

In all ecosystems you will find producers. These are organisms which are able to make their own food by photosynthesizing sun light (see more info on photosynthesis). You will also find consumers within an ecosystem and these are organisms which eat other organisms as a source of energy. This forms the beginning of the food chain.

Producer → Primary Consumer → Secondary Consumer → Tertiary consumer

Measuring Biomass & Chemical Energy

Biomass has traditionally been measured in terms of the dry mass of it’s tissue per unit area per unit time. This means you can you find the amount of biomass in some tissue by drying it (leaving it or placing it in an oven or heater until the tissues weight becomes constant).

This tissue sample can be tested for it’s level of chemical energy by burning it, the energy release can be measure in joules (J). It can also be measured by heating up water and the temperature measured, the greater the rise in temperature of the water the more chemical energy the biomass has.

GPP (Gross Primary Production) – total amount of chemical energy converted by producers within an ecosystem using light.

NPP (Net Primary Production) – given that ~50% of GPP is lost as heat (R) the NPP is the remaining chemical energy. This is the energy which will be stored for later use and is the energy which will also be passed up the food chain if not used first.