Measuring distribution and abundance 23.5

Question 1

Why would you need to measure the distribution and abundance of organisms?

Answer 1

To measure the biodiversity

Question 2

What is distribution?

Answer 2

Distribution is where organisms are found within an ecosystem

Question 3

Why is distribution uneven?

Answer 3

Organisms will all live where their abiotic and biotic favour them, so where they have the bets chance of survival and where predation is low

Question 4

How could you measure the distribution of organisms?

Answer 4

A line or belt transect can be used where you lay down a line or belt and take samples at regular intervals

Question 5

Why is a belt transect better than a line transect?

Answer 5

Because it provides more information, you mark two parallel lines and take samples within that rectangular area. A line transect is just a sample at intervals on a line

Question 6

What type of sampling are line and belt transects?

Answer 6

Systematic sampling because it’s non-random and it uses a specific system.

Question 7

Why is systematic sampling better than random sampling in this scenario?

Answer 7

Because it can allow scientists to study how abiotic factors affect different areas and how this affects the distribution of the species.

Question 8

What is abundance?

Answer 8

The number of organisms present within an area of an ecosystem at a certain time

Question 9

Why can abundance change easily?

Answer 9

Birth and immigration increase it Death and emigration decrease it

Question 10

What is the definition of population?

Answer 10

Population is a group of similar organisms in a given area.

Question 11

Why can you rarely count a population and what do you do instead?

Answer 11

Populations can rarely be counted because it is too time-consuming, there may be too many organisms or it could damage the environment. Instead, you use sampling

Question 12

Why can sampling never be completely accurate and how do you increase its accuracy?

Answer 12

It can’t be completely accurate as you are only looking at a small selection of the population, it probably won’t be completely representative. The greater your sample size, the more accurate it will be as it’s a closer representation

Question 13

How do you measure plant abundance?

Answer 13

You place quadrats randomly and count the number of organisms inside of them.

Question 14

The formula for plant abundance

Answer 14

Estimated pop no = number of individuals in sample / area of a sample (m^2)

Question 15

How do you measure animal abundance?

Answer 15

You cannot use quadrats so you can use the capture, mark, release recapture technique or pooters, sweep nets etc…

Question 16

What is the capture-mark-release recapture technique?

Answer 16

-You capture as many individuals as you can in your sample area - You tag them or mark them - You release them back into their habitat and allow them to redistribute themselves - You recapture as many as possible and record the number of marked and unmarked individuals - Use the lincoln index to calculate pop size

Question 17

What are the limitations of the capture-mark-release-recapture technique

Answer 17

• Doesn’t represent the entire population - Doesn’t take into account birth or death - Mark could rub off - Makes animals more visible to predators

Question 18

What is the lincoln index?

Answer 18

Estimated pop size = no of organisms in sample 1 x no of organisms in sample 2 / no of recaptured

Question 19

How do you calculate the biodiversity once you have found the pop size?

Answer 19

You use the Simpsons Index of Diversity which tells you the biodiversity present

Question 20

What is the Simpsons index of biodiversity?

Answer 20

D = 1 - sum (n/N) squared D= diversity index N = total organsisms in ecosystem n = no of individuals of each species

Question 21

What do the results of simpsons index represent?

Answer 21

If its 0, there’s no biodiversity present, if its 1 there is infinite biodiversity present