Distribution of Organisms Flashcards Preview

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Flashcards in Distribution of Organisms Deck (15):

What is a habitat?

The place where an organism lives.


Where an organism is found is dependent on environmental factors... these include...(5)







Availabitlity of water

Availability of O2 and Co2.

Availability of nutrients

Amount of light


Collecting environmental data..

1. Reliability

What tools are good for finding out how an organism is distributed? (2)

Quadrats and transects


Collecting envrionmental data..

1. Reliability

How do you make sure your results are reliable? (R+R)

You must take a ... why?

Use... samples.. why?

Make sure they are repeatable and reproducible. 

Large sample size, give a better representation of the whole population.

Use random samples ... to make sure they are reproducible,

...this will not happen if you take 3 samples, all in the same area.


Collecting environmental data..

2. Validity

For results to be valid they must be...

How do you do this (V)

When this is done what does this show...


Control all the variables

If a difference in distribution is due to a singular environmental factor.


What is a quadrat?

What is it used for?

A square frame enclosing a known area, e.g. 1m2

To compare how common an organism is in two sample areas.


An example of why a species may be more common in one area than another... in a field

Daisies are more common in the open than under the trees, due to the light levels ( one environmental factor)


How do you compare how common an organism is in two sample areas?

Where do you put it...


Maximum results...

Work out...

Sample area 2...

Place the quadrat on the ground ata random point within the sample area.

Count all the organisms within the quadrat.

Reapeat the steps as many times as you can.

Work out the mean number of oragisms per quadrat within the first sample area.

Do all the steps above in another sample area and compare the two means.


What are the two ways to study the distribution of organisms?

Measure how common an organism is in the two sample areas, using quadrats, then compare them.

Study how the distribution changes across an area by placing quadrats along a transect.


What do you use transects for?

To help find out how organisms are distributed across an area, for example if an organism becomes less common as you move towards a hedge.


What is the distribution of an organism?

Where an organism is found, e.g a section of a field


Where an organism is found is dependent on ....

environmental factors...


How do you use a transect? (set up etc)

Mark out....


Mark out a line in the area you want to study

Collect the data along the line by counting the organisms touching the line, or inside the quadrats placed underneath.



Why could an organism be more common in one area? (F)

Due to differences in environmental factors between the two areas.


How do you work out population size? (2)

Work out the mean numer of oragnisms per m2 using the quadrat.

Multiply the mean by the total area.