Unit 2 - Distribution of organisms

Question 1

Name the environmental factors that effect the distribution of organisms (7)

Answer 1

• Avaliability of food
• Light
• Temperature
• Carbon dioxide
• Water
• Oxygen
• Nutrients

Question 2

Where do organisms live?

Answer 2

Where they can survive, aka where they can get access to the things they need to survive

Question 3

Name the 2 sampling techniques

Answer 3

• Systematic sampling
• Random sampling

Question 4

Explain systematic sampling

Answer 4

This is done using transects, it is used to observe changes in distibution across areas of the habitat

Question 5

Explain random sampling

Answer 5

This is done using quadrats, it is used in areas where distribution is quite uniform

Question 6

Why is random sampling done?

Answer 6

Random sampling is done because counting each individual organism would be to difficult and take too long. We use quadrats to estimate the unmber of organisms in an area

Question 7

What do we need to do when doing random sampling

Answer 7

• Avoid bias
• Get an accurate reading that is representative of the area

Question 8

Explain how random sampling is done

Answer 8

1. Divide the area into a grid using tape measures
2. Generate a random numbers (to avoid bias)
3. Use pairs of random numbers as co-ordinates to plate the quadrats into a field
4. Use a large number of quadrats (more than 10) to be representatuve of the area and to improve the reliability of the results
5. Counts the numbers of fauna in the quadrat
6. Calculate the mean/average number of fauna in each quadrat
7. Multiply the mean number of fauna in 1 quadrat by the total number of quadrats that would fit into the area

Question 9

Counting the number of species in a quadrat can be difficult if:

• there is a large number of the species
• its difficult to determine individual plants of the species

What is the solution to this?

Answer 9

Etimated percentage cover

Question 10

Why are transects used?

Answer 10

Transects are used to investigate how distribution changes across an environment gradient

aka how species change as the conditions in the habitat change

Question 11

Explain the process of building a transect

Answer 11

1. Stretch a tape from under the trees out into the field - this is the transect
2. Place quadrats at regular intervals along the transect
3. Record the desired information

aka - number of different species in the quadrat, number of particular species in the quadrat and the percentage cover of species

4. Repeat with more transects to get data thats representative

Question 12

Why do we build transects? (6)

Answer 12

• To inform concervation measures
• To identify the conditions needed for survival
• To detirmine the stability of a habitat/ecosystem
• To identifY the impact of human influence
• To identify warning signs about species in decline
• To loos at seasonal changes in species

Question 13

Name some of the traps used to collect animals

Answer 13

• Pitfall traps - dry pitfall traps consist of a container buried in the ground with its rin at the surface level used to trap mobile animals that fall into it, wet pitfall traps are the same but contain a solution designed to kill and preserve the trapped animals
• **Beating tray **- (a cloth that is stretched out using a frame) the frame is held under a tree and the foliage is shaken, collecting the falling invertebrates
• Kick sampling - done by facing the net upstream and kicking vigorously in front of it, botton-dwelling invertebrates are swept into the net
• Pooters
• Longworth Trap
• Smoke Manchine