Distribution of organisms

Question 1

What is the distribution of an organism?

Answer 1

Where an organism is found i.e. a part of a playing field.

Question 2

Which 6 environmental factors effect the distribution of an organism?

Answer 2

1. Temperature
2. Availability of water
3. Availability of oxygen
4. Availability of carbon dioxide
5. Availability of nutrients
6. Amount of light

Question 3

Why might an organism be more common in one area compared to another?

Answer 3

Because of differences in environmental factors i.e. more light might mean more daisys

Question 4

What are the two ways to study the distribution of an organism?

Answer 4

1. Measure how common an organism is in two sample areas (e.g. using quadrats) and compare them
2. Study how the distribution changes across an area e.g. by placing quadrats along a transect

Question 5

What is a quadrat?

Answer 5

A square frame enclosing a known area e.g. 1m squared

Question 6

What are the 6 steps to comparing how common an organism in 2 sample areas?

Answer 6

1. Put the quadrat down at a random point within the 1st sample area. (could divide into grid and use a number generator to do this)
2. Count all the organisms within the quadrat.
3. Repeat the first two steps as many times as possible.
4. Work out the mean number of organisms per quadrat within the first sample area (Q on different card)
5. Repeat previous steps in the 2nd sample area.
6. Finally compare the two means. e.g. you might find 2 daisies per m squared in the shade, and 22 per m squared (lots more) in the open field.

Question 7

How do you find the mean number of organisms per quadrat within your chosen sampling area?

Answer 7

You list the number of organisms you found in each quadrat in your chosen sample area like so:
18, 20, 22, 23, 23, 23, 25
Mean= TOTAL number of organisms/ NUMBER of quadrats= 154/7= 22 organisms per quadrat

(easy maths)

Question 8

What is extremely important to do when taking a sample?

Answer 8

Putting down your quadrat in a RANDOM place- chucking it over your shoulder is better than placing t down on the first big patch of organisms you come to.

Question 9

Which other averages might you need to find when working out the distribution of organisms, and how do you do so?

Answer 9

MODE: most common
MEDIAN: middle value

Question 10

How do you work out the population size of an organism in one sample area?

Answer 10

1. Work out the mean number of organisms per m squared. (If your quadrat = 1m squared and you’ve worked out the mean already then you’ve already done it)
2. Multiply this mean by the total area

e.g. 22 daisies per m squared, area of an open field is 800m squared, then the size of the daisy population is 22 X 800 = 17 600

Question 11

What do transects show?

Answer 11

Transects show how organisms are distributed along a line/ across an area.
e.g. if an organism becomes more or less common, or has the same distribution, as you move from a hedge towards the middle of a field.

Question 12

What are the 2 steps in using a transect?

Answer 12

1. Mark out a line in the area you want to study using a tape measure.
2. Collect data along the line.

Question 13

What are the 2 ways you can collect data along a transect?

Answer 13

1. Counting all the appropriate organisms that touch the transect.
2. Placing quadrats next to each other or at intervals along the line, for example every 2m.

Question 14

Which 2 things do you need to think about when collecting data?

Answer 14

1. Reliability

2. Validity

Question 15

What makes results reliable?

Answer 15

Making sure they are repeatable and reproducible.

Question 16

How can you make your results more reliable? Why does this help?

Answer 16

By taking a larger sample size

e.g. Using as many quadrats and transects in your sample area as possible, extending the boundaries of your sample area, using smaller quadrats to have more accurate means etc.

Bigger samples are more representative of the whole population.

Question 17

Which 2 factors constitute valid results?

Answer 17

1. Your results must be reliable.

2. Your results must answer the original question.

Question 18

How must you carry out you investigation to ensure you answer the original question (thus making your result valid)?

Answer 18

To answer the original question you need to control all of the variables.

e.g. if you want to find out whether the difference in distribution between 2 sample areas is due to environmental factors, and someone comes, makes a daisy chain from one of your samples, and leaves with it, you have not controlled the variables and your results will be effected.

Question 19

What can help improve the validity of your results? Why?

Answer 19

Using random samples.

If your samples are all in one spot, and everywhere else is different, the results you get won’t be valid.