4.5b Food Webs

Key points:
1. The food web allows people to provide a much better description of an ecosystem. The eco system is composed of organisms within a community interacting, and in this case that interaction is feeding.
2. The food web shows organisms feeding at different trophic levels
3. Feeding at different trophic levels has consequences, organisms can have multiple predators, or organisms feeding on multiple prey. This results in the linking of food chains.
4. In this case, the producer is grass. The primary consumers are rabbits, beetle, slugs, mice. The woodlice would also be considered a primary consumer. The secondary consumers would be the small bird, badger.
5. The grass is eating by the rabbit, the hawk eats the rabbit, making it a secondary consumer. However, if the hawk feeds on the small birds as well its acting in the tertiary consumer.
6. The slug is the prey to birds and hedgehogs.
7. The fox is feeding on mice, rabbits and shrews, making links in the food chains.

4.5a Food Chains

Key Points:
1. The food chain linked together the producer to the primary consumer, to the secondary consumer and possibly over to the teritiary consumer.
2. At the moment, there is only one organism per trophic level.
3. In a food chain, omnivores cannot be shown
4. Food chains show the flow of matter and the flow of energy.

4.4 Tropic levels

Key Points:
1. The word trophic means to feed. Names given to the different feeding levels.
2. The carrot plant is doing photosynthesis, the carrot fly is eating the carrot plant and it makes it a herbivore. Higher up in the chain would be the fly catcher, presumably some sort of bird, making it a carnivore. And finally, the animal that feeds upon the flycatcher would the the top food carnivore.
3. However there are other names, the carrot plant would be called the producer. Producers convert light energy into chemical energy. The carrotfly would be called the primary consumer. The primary consumer takes in the chemical energy of the plant and turns it into the chemical energy OF the fly. The flycatcher is the secondary. This is again changing the chemical energy. The next feeding level is called the teriary consumer. Taking in the molecules of the fly catcher, and the chemical energy is made into the tertiaries chemical energy instead.
4. When they die, there are a special type of organisms called decomposers which dispose of the body. There are two, fungi and bacteria.
5. They break them down into nitrates and phosphates.

4.3 Quadrates samples

Key points
1. The quadrating technique can be used to sample the population distribution of organisms within their habitats.
2. The quadrat sample must be random, so there is no bias
3. It also has to be representative, a large enough sample which is similar to the true population
4. A grid system works very similarly to the X Y coordinates on a graph, and the grids are supposed to be equal sizes.
5. A random number generator can be used to randomly choose a number on the x axis and on the y axis, so that there is a quadrat to be examined without bias
6. Once the quadrat has been found, counting the organisms, in this case daisies, will show you how many there are.
7. A representative sample must be found, ideally the bigger the better
8. It can be found in about 10 quadrats
9. The data must be collected in a table, like this:

Quadrat                  Number of daisies (per mete squared)
     1                                                       x
     2                                                       y
     3                                                       n

10. Once the collection has finished, we would add up the 2nd colomn, and divide the total by the number of quadrats., to find the mean.

4.2 Quadrates

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4.1 Ecosystems

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