Determining Population Size

Question 1

What are the two categories of techniques for determining population size?

Answer 1

• direct methods
• indirect methods

Question 2

What determines the choice regarding which method to use when determining population size?

Answer 2

• the size of the organisms
• the mobility of the organisms

Question 3

How do direct methods work in terms of the counting of the individuals in the population?

Answer 3

Direct methods involve the total count of ALL individuals in the population

Question 4

When are direct methods used?

Answer 4

Direct methods can only be used for populations where the organisms are large enough to be seen and the area in which the animals are being counted is not too large

Question 5

What is the direct counting of individuals called?

Answer 5

A census

Question 6

What do census methods include?

Answer 6

• direct contact counting of smaller-sized organisms or humans
• direct counting from vehicle/helicopter/plane of larger organisms
• counting from aerial photographs taken of larger moving organisms

Question 7

For which individuals can direct methods be used?

Answer 7

• slow moving (snails, tortoises)
• stationary (plants)
• usually stay in fixed position (barnacles, mussels)

Question 8

How do indirect methods work in terms of the counting of the individuals of the population?

Answer 8

Indirect methods involve the counting of only PART of the population

Question 9

What are the indirect methods used to determine population sizes?

Answer 9

• mark-recapture technique
• quadrat technique