Sampling organisms, Carbon cycle Flashcards
Explain how the effect of the levels of abiotic factors varying from place to place
The levels of abiotic factors can vary from place to place
This affects the number of different organisms that we find in any location
What is sampling
A technique used by scientists to determine the number (OR ABUNDANCE) of a species/organisms in an area/ecosystem
Two types of sampling
Two ways to perform sampling
Random sampling
Sampling along a transect
What is random sampling
Random sampling is used to compare the number of organisms in different areas
What equipment is needed to perform random sampling
To do random sampling, a quadrat is used
What is a quadrat
A quadrat is a wooden or plastic square
Describe random sampling
Random sampling is used to compare the number of organisms in different areas
To do this, we use a quadrat
- In random sampling, the quadrat is placed at random locations across the area. One way to do this, is to use random numbers to select the different locations
- To use a quadrat, we place it on the ground and then count the number of organisms inside the quadrat.
This technique can be used to sample plants or slow-moving animals - We move the quadrat to a different random location and count the number of organisms there
- Keep doing this until we have sampled a large number of random locations
it very important that we place the quadrat a large number of times
THIS MAKES IT MORE LIKLELY THAT WE GET VALID RESULTS
- We move to the next area that we are comparing and we repeat.
We randomly place the quadrat the same number of times as before and count the numbers of different plans
This technique allows us to compare the numbers of different species of organisms in two different areas
from this we can determine if a hypothesis is correct or not (from this we can see that our hypothesis is correct, we do find fewer ferns in the light conditions compared to the dark conditions)
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1.choose a starting point on the school field in an area where the grass is often cut
2.use random numbers to generate a set of coordinates to place your first quadrat
3. count the number of different plant
species within this quadrat (the species richness)
4. return to your starting position and repeat steps two and three a further 14 times using different random numbers
5. repeat steps one to four for a part of the school field which the grass is infrequently cut
6. compare your results by calculating a
mean for each location
Hypothesis: Fewer ferns are found in light conditions than in dark conditions
What type of sampling would be used and why
Random sampling - because we are comparing two different areas
Why is it very important that we place the quadrat a large number of times
it very important that we place the quadrat a large number of times
it makes it more likely that we get valid results
if we place the quadrat only once, this might not give us a sample which accurately represents the whole area
(if the quadrat is only placed in an area where there are fewer flowers )
equation - use random sampling to estimate the total population size of a species in an area
total population size = total area/area sampled x number of organisms of that species counted in sample
How to carry out sampling along a transect
In order to investigate whether the numbers of species change as we move across a habitat.
To do this, we use sampling along a transect
A transect is simply a line such as a tape measure or a piece of rope
We place the transect line so it runs across the habitat that we are looking at
We then use a quadrat to count the number of organisms at intervals on the transect
place a tape measure on the dune running from the beach inland
place the first quadrat at the start of the transect and we count the different organisms in the quadrat
Then move the quadrat closer inland (across the habitat) by a set distant for example two metres and count the number of plants again
We keep doing this as we move further inland (across the habitat)
It is important that we carry out this transect a number of times to get valid results
To do this, we move the tape measure along and repeat the whole process
This way we can get valid data, on how the numbers of the different species change across the dune/habitat
when to use a transect
In order to investigate whether the numbers of species change as we move across a habitat.
To do this, we use sampling along a transect
we use sampling along a transect to see how the numbers of organisms change across a habitat
what is a transect
a line such as a tape measure or a piece of rope
Describe how to measure the population size of a common species in a habitat
Estimating the total population of daises in a field
In order to estimate the total population of daises in a field, use random sampling
in random sampling, we use a quadrat like this one.
Use a quadrat that has a known area - e.g. 0.5 by 0.5
1.choose a starting point on the field (ensure that you measure the area of the field)
2.use random numbers to generate a set of coordinates to place your first quadrat
3. count the number of daises
species within this quadrat (the species richness)
4. return to your starting position and repeat steps two and three a further 14 times using different random numbers
5. Keep a total of the total number of daises that were counted across the 15 quadrats
6. To estimate the total population of daises in the whole field, use the equation.
ensure you know the area of both the quadrat and the field.
total population size = total area/area sampled x number of organisms of that species counted in sample
Explain why the population size estimated using quadrats is only an estimate
It is only an estimate because it is possible that our 15 quadrat throws do not represent the whole area.
e.g. there might be regions within the area with a much higher or lower number of daises/organisms than the average
