Ecology in the Local Environment Revision Pack (B4) An ecosystem is made up of all of the plants and animals that live there and their surroundings.

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1 Distribution of Organisms: An ecosystem is made up of all of the plants and animals that live there and their surroundings. A habitat is simply where an animal or plant lives. The community, just like in humans, is made up of all of the different plants and animals living in a habitat. The number of a particular plant or animal in that habitat is called its population. If London, local community is diverse, it means it houses a variety of different people from all walks of life. In natural ecosystems, like lakes or woodland, there is a variety of plants and animals living there this is known as biodiversity. Most artificial (unnatural or man-made) ecosystems have poor biodiversity as they house one or two types of plant or animal. In artificial ecosystems, like fish farms, humans protect ONLY one species and generally take any other organisms out of its habitat that could: - Complete with it - (and in doing so) Reduce the yield of that organism A transect line is used as to map the distribution of organisms in a specific habitat. STEP 1 a long piece of string is laid out across an area, like a sea shore (as seen to the left) STEP 2 At regular intervals along the line, quadrats (square frames) are placed on the string STEP 3 - The amount of animals can be counted that are present within the area, and the (average) percentage cover can be calculated for plants The information collected can be put in a kite diagram (right). This highlights the distribution of organisms. The larger the surface area of each kite, the more organisms there were in that area. Zonation in the habitat is shown in the diagram to the right. This zonation is not caused by anything biological but more abiotic (or physical) factors like availability of water, exposure and ph. For example, the mosses in the diagram to the right can survive in a variety of areas and can withstand dry and poor conditions. An organism like a fern lives away from the footpath and thrive in wetter and more protected areas away from the footpath.

2 Organisms in ecosystems are self-supporting and interdependent (dependent on each other for survival). In food chains, all animals depend on plants both directly and indirectly energy is transferred from one organism to the next. The gases in the air are balanced because of photosynthesis (which removes carbon dioxide and given off oxygen) and respiration (which removes oxygen and gives off carbon dioxide). The only thing that ecosystems need from outside is the sun as its energy source. Population Size: Population size can be estimated by obtaining data from a small sample and scaling up. For example, quadrats (see left) are often used to determine a larger value of organisms in a specific area by scaling up. E.g. Callum has a very large front garden. He wants to find out how many daffodils are in his garden. Firstly, he uses a suitable sample of quadrats (perhaps 10) and places these at random areas around his garden by throwing them with his eyes closed. Next he measures the amount of daffodils in each of these 1m 2 quadrats. There are 3, 6, 4, 2, 4, 5, 3, 4, 3 and 5 daffodils in each of these quadrats respectively. The mean is therefore 3.4 or 3 daffodils per 1m 2. His garden is 30m 2 so 3 x 30 = 90. This means there s approximately 90 daffodils in his garden. Capturing animals can be done in a number of ways. For example, the first picture above (from left to right) is called a pitfall trap this is where there s a small container buried in the ground collects small insects and animals, these are then counted and identified. The second is a pooter, whereby insects can be sucked up via a collecting tube into the chamber, counted and identified. The third is simply a net this is used to collect air-borne insects like butterflies and animals as well, like fish. The fourth is the capture-recapture method; in which you follow the following steps: STEP 1 You capture insects or animals using the most appropriate technique STEP 2 You then count how many there are and put a dot of paint on them (as seen in the image) STEP 3 You release them back into the habitat STEP 4 You let time pass, and capture insects and animals again STEP 5 You use the formula to work out the population of that specific animal or insect in the community: Population Size = Number in 1 st Sample x Number in 2 nd Sample Number in 2 nd Sample that had been previously marked

3 Additional NOTES: The bigger quadrats you use or the more samples you take make the estimations more accurate. The capture-recapture method estimate may be slightly unreliable because: - The method assumes that no new plants/animals have been born and that no plants/insects have died in that area in between the two samples - The markings may affect the survival of the insect when it is released, meaning it will NOT return Identical sampling methods MUST be used for both the original and second sample.

4 Past Papers: PPQ(1):

5 Continued on next page... Ecology in the Local Environment Revision Pack (B4)

6 PPQ(3):

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8 Mark Schemes: PPQ(1): PPQ(2):