Ecosystem methods

Question 1

1. What is meant by uniformly distributed?

Answer 1

Organisms are equally spread;

Question 2

2. What is meant by:
   a- species richness

Answer 2

a- the number of different species present

Question 3

b-species frequency

Answer 3

b-the number of times a species occurs in the habitat as a proportion of the number of sites samples

Question 4

c-population density

Answer 4

c-the number of a certain species per unit area

Question 5

d-population size

Answer 5

d-the total number of individuals in the population in an area

Question 6

e-percentage cover

Answer 6

e-the percentage of a given area covered by the organism. Used for organisms that do not have distinct individuals such as moss.

Question 7

3. Outline a method to determine species richness

Answer 7

Create a large grid and use a random number generator to generate coordinates; Use a large number of quadrats at the random coordinates; Count the species present in each quadrat; the total number of different species is the species richness

Question 8

4. Describe how you would investigate the percentage cover of plants in an area

Answer 8

Create a large grid and use a random number generator to generate coordinates; Use a large number of quadrats at the random coordinates; Estimate the percentage cover of each species of plant at each coordinate; calculate a mean

Question 9

5. Outline a method to investigate succession/a changing environment across a distance.

Answer 9

Lay a tape measure out from one side to the other; Place quadrats at regular intervals along the line; Count the plants or estimate the percentage cover; Repeat for more than one transect;

Question 10

6. Describe how you could use Mark-release-recapture to estimate population size.

Answer 10

Collect a sample, mark them and release; Ensure the method of marking does not cause harm or make them visible to predators; Leave sufficient time to distribute randomly in the population before collecting the second sample; Use the equation
Number in first sample x number in second sample
Number of marked in second sample

Question 11

7. What assumptions are made in mark-release-recapture?

Answer 11

Marking is not removed and does not affect survival; there is no immigration or emigration; sufficient time is left to mix with the population; there are no births or deaths; each sample is collected by the same method

Question 12

8. How do you estimate the population number of a motile species?

Answer 12

Number in first sample x number in second sample
Number of marked in second sample

Question 13

9. When using capture, mark, recapture in large habitats, why might the estimated population size be unreliable?

Answer 13

In large habitats there is less chance of recapturing the marked individuals OR unlikely the organisms distribute randomly since the habitat is so large.

Question 14

10. How do you use a point quadrat?

Answer 14

Place the quadrat on the ground in a random place. Where the points touch the ground record the species/number of plants.

Question 15

11. Give the difference between percentage cover and species frequency.

Answer 15

Percentage cover is an estimate of coverage in the quadrat, species frequency requires counting the number of species

Question 16

12. Explain how to find the population density of non-motile organisms on a habitat.

Answer 16

• Create a large grid and use a random number generator to generate coordinates; Use a large number of quadrats at the random coordinates;
• Count the number of individuals in the quadrat
• Repeat many times
• Find the mean
• You now you have the mean number per m2-this is the population density

Question 17

13. Explain how to find the species frequency of non-motile organisms in a habitat

Answer 17

• Create a large grid and use a random number generator to generate coordinates; Use a large number of quadrats at the random coordinates;
• If the species is present in the quadrat at each location mark it as present
• divide the number of quadrats where a particular species is found is recorded by the number of quadrats (sample sites)
• e.g. a quadrat was placed down 50 times in an area and dandelions were found in 12 of these quadrats therefore the frequency of dandelions is:
• 12/50 x 100 =24% dandelions.

Question 18

14. Explain how to find the population size/total number of non-motile organisms in a habitat

Answer 18

• Create a large grid / divide field into squares.
• Use a random number generator to generate coordinates;
• Use a large number of quadrats at the random coordinates;
• Count the number of individuals in the quadrat
• Repeat many times.
• Find the mean number of plants per quadrat
• Calculate how many there would be in 1m2
• You now you have the mean number per m2
• Multiple by the area of the habitat
• Alternatively to work out the number to multiply the mean by you could do (area of the habitat÷ area of one quadrat)