21/07/2011 16:21← IGCSE Biology←

← Section 4: Ecology and the environment← a. Organisms in the environment←

← 4.1 understand the terms population, community, habitat and ecosystem←

← 4.2 explain how quadrats can be used to estimate the population size of an organism in two different areas←

← 4.3 explain how quadrats can be used to sample the distribution of organisms in their habitats.←

← Green book reference: p152-154←←

Definitions 21/07/2011 16:21← IGCSE Biology←

← Section 4: Ecology and the environment← a. Organisms in the environment←

← 1. Definitions← 4.1 understand the terms population, community, habitat and ecosystem←

← Ref:← Pg. 159 15.1 Organisms interact with their environment← Ecology uses special terms←

← Read the relevant sections in your book.

← Write out a definition and give an example for each word in the objective.←

← Population ← Total number of organisms of same species, in same area at same time←

← Community ← All the different populations in a given area interacting together←

← Habitat ← Place where an organism lives←

← Ecosystem ← All the biotic (living) and abiotic (non-living) interactions in an area.← It consists of the community in its environment.←

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21/07/2011 16:21←

← IGCSE Biology←

← Section 4: Ecology and the environment← a. Organisms in the environment←

← 2. Quadrats← 4.2 explain how quadrats can be used to estimate the population size of an organism in two different areas←

← 4.3 explain how quadrats can be used to sample the distribution of organisms in their habitats.←← Introduction ← A quadrat is a square frame used for sampling an area.

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← Quadrats can be used to sample an area either systematically or randomly. ←

← Random sampling is particularly useful if two habitats are being compared. For random sampling, every point in the sample area has an equal chance of being sampled. If enough samples are taken, the results should be representative of the whole sample area.←

← Systematic sampling is used to investigate changes in a habitat caused by one environmental factor. The best way to measure these types of changes is to use a transect. ←

← Sampling within a quadrat ←

← The simplest way to process the results of quadrat surveys is to count the number of plants found in each quadrat. Where each plant is a discrete individual, such as dandelions and daisies, this is acceptable. When all the results have been collected, calculate the mean number of plants per quadrat for each of the sample areas. ←

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21/07/2011 16:21←← IGCSE Biology←← Section 4: Ecology and the environment← a. Organisms in the environment←← 3. Quadrat Sampling←← 4.2 explain how quadrats can be used to estimate the population size of an organism in two different areas←← 4.3 explain how quadrats can be used to sample the distribution of organisms in their habitats.

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← Example←← Imagine there are 8 plants in the quadrat←← This quadrat is 0.5m2 ← The lawn is 2.5m x 3.5m = 8.75m2

←← Image you did this 4 more times in order to get 5 results and the results were:

←Quadrat Number of

plants1 102 73 94 75 11

←←← Considering your results← Estimate the total number of each plant in the lawn by doing this calculation:←← total number of plants counted ← total area sampled (in m2) = number of plants per m2

←← number of plants per m2 x total area of lawn (in m2) = total number of plants on lawn←← (10+7+9+7+11) = 44 plants = 44/2.5 = 17.6 plants per m2

← (0.5 x 5) = 2.5m2

←← 17.6 plants per m2 x 8.75m2 = approximately 154 plants on the wasteland←← Grass Biomass of the school field ←← Method ← 1) Count the number of grass blades in a 10x10cm quadrat← 2) collate the class results using excel to establish an average← 3) Go to the website to estimate the size of the field← 4) Estimate the number of blades of grass on the whole field← 5) Weigh a blade of grass using the balance← 6) Use this to estimate the biomass of grass on the field. ←←

21/07/2011 16:21← IGCSE Biology

←← Section 4: Ecology and the environment← a. Organisms in the environment←← 3. Quadrat Sampling← Recall the use of quadrats to estimate the population size of an organism in two different areas.←← Estimate the total number of each plant in the lawn by doing this calculation:←← total number of plants counted ← / total area sampled (in m2) = number of plants per m2

←← number of plants per m2 x total area of lawn (in m2) = total number of plants on lawn←← The Wasteland ←

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