Revision:Investigating an Ecosystem

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Investigating an Ecosystem is one of three sections in The Biosphere unit in Standard Grade Biology.

An ecosystem is a biological unit made up of living and non-living parts. It is the relationship between the members of a community and their habitat. Examples of ecosystems are woodland, pond and loch. There are a few key definitions that you must memorise:

• Habitat- Where an organism lives (eg. a burrow in the soil)
• Community- All the plants and animals that live in a particular area
• Population- All the organisms of one particular species

To study an ecosystem, it is necessary to find out what kind of organisms live there and how abundant (rare or common) these organisms are. It would take too long so biologists take samples. A quadrat is one piece of equipment that is used. It is a rectangular frame used to sample plants. The quadrat must be placed randomly so the results are representative of the area as a whole. Several samples (at least 10) must be taken and an average abundance calculated. This makes the results more reliable. A pitfall trap is another piece of equipment biologists use to sample insects moving across the surface of the ground. It is important that the trap is flush with the ground (so insects can't avoid it), is camouflaged (so predators don't eat the insects) and is checked regularly (prevents insects eating each other).

There are many different factors which can affect the number of organisms in an ecosystem. Factors related to living things are biotic factors and factors relating to non-living things are abiotic factors. Examples of biotic factors include: food, predators and disease. Examples of abiotic factors include: light intensity, soil moisture, temperature and wind speed. Some abiotic factors are easily measured. A light meter can be used to measure the light intensity of a certain area. It is important for the sensors on the meter to be aimed at the brightest light source (usually the sun) and to make sure the user is not casting a shadow over the sensors. Soil moisture can be measured using a moisture meter. It is important to clean the probe after each use to prevent any contamination from previous tests affecting the results. Abiotic factors affect the distribution of organisms. Less plants are to be found in a forest compared to an open field as the trees block out the sunlight and there is not enough light for the smaller plants to use during photosysnthesis.