4.5b FOOD WEBS

importance of food webs
a food web helps us to describe an ecosystem, it shows the community of different species interacting in the form of feeding.

a food web shows organisms feeding at different trophic levels. this means an organism can have multiple predators and prey this results in the food chains within the ecosystem being linked.

4.5a FOOD CHAINS

a food chain links together all the trophic levels --> producer, primary consumer, secondary consumer, tertiary consumer.

in a food chain:

-     there is only one organism shown at each trophic level.

-     you cannot show an animal as an omnivore

-     you cannot show animals feeding at more than 2 trophic levels

a food chain shows the flow of matter and also shows the flow of energy.

4.4 Trophic Levels

TROPIC IS TO FEED

trophic levels are levels of which animals in an ecosystem feed in, including producers, primary consumers, secondary consumers, tertiary consumers and decomposers

CARROT PLANT :            CARROT FLY                      FLY CATCHER                SPARROW
is a producer, transfer's        primary consumer,                 carnivore, secondary             top carnivore,
light energy into      -----> takes in chemical energy -----> consumer, takes in the -----> tertiary consumer
 chemical energy                of the plant into chemical       chemical energy of the         the sparrow turns the
through photosynthesis.      energy of the fly.                   carrot fly and turns it into    chemical energy of the
                                                                                          the chemical energy of the   flycatcher into the
                                                                                          fly catcher.                         chemical energy of the
                                                                                                                                     sparrow

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DEATH all living organisms die at one point, at this point they get broken down by a group of organisms called decomposers, examples of decomposers are funghi and bacteria, decomposers break down dead animals into nitrates and phosphates.

4.3 Quadrates samples

using the quadrate technique in sampling the distributions of organisms in their habitat.

the sample has to be :
-  random ( not biased )
-  representative ( large enough )

how to carry out quadrate SAMPLES:
-  separate the area in the field into a grid working like the x y coordinates of a graph
-  generate 2 random numbers representing the x coordinate and the y coordinate
-  find the coordinate on the graph, and then in the real area
-  count the number of species you are trying to compare in that particular square
-  the experiment is repeated

REPRESENTATIVE sample
a representative sample is one large enough, the bigger the better, the larger the sample is the closer it is to the real value of the field.

the data is recorded in a table, the average is found ( number of species in all data collected/number of quadrates)
this experiment cam show the average population of a particular species in one particular area, results can also be used to compare the population of the same organism in another area.

4.2 QUADRATES

use of quadrats to estimate population size of a organism in two different areas.

QUADRATING :: are based on squares, these squares can be made out of any material
they are used to sample different areas by counting populations in the square to give an estimation of the size of the community and so results can be compared with the results from another area.

4.1 ECOSYSTEMS

TERMS USED TO DESCRIBE ECOSYSTEMS

HABITAT - abiotic
includes abiotic factors ( non biological )
- cycle of daylight
- temperature
- climate
- rainfall
- humidity
- slope of land (aspect/gradient)
- geology
- latitude
- longitude

COMMUNITY OF ORGANISMS - biotic
the populations of different species that are interactive in a habitat
population : number of individuals of a particular species
species: organisms that reproduce fertile off spring
interacting : feeding (foodchain / food webs)

ECOSYSTEM :: our ecosystem is a community of organisms in a particular habitat, the community is made up of different species interacting within that particular habitat.