Investigating populations

Question 1

Define abundance

Answer 1

The number of individuals of a species in a given space

Question 2

What must samples be in order for findings to be considered valid?

Answer 2

Representative

Question 3

What 3 factors must be considered when using quadrats?

Answer 3

The size of the quadrat to use, the number of sample quadrats to record within the study area, the position of each quadrat within the study area

Question 4

What will affect the size of the quadrat to use?

Answer 4

The size of the plants or animals being counted and how they are distributed within the area

Question 5

What affects the number of sample quadrats to record within the study area?

Answer 5

The larger the number of sample quadrats, the more reliable the results will be. Time availability also influences the number of sample quadrats

Question 6

What must be collected to produce statistically significant results?

Answer 6

A large, random sample

Question 7

Why must sampling be random?

Answer 7

To avoid bias and ensure that the data obtained is valid

Question 8

How do you ensure a random sample?

Answer 8

Obtain a series of coordinated by using random numbers taken from a table or generated by a computer

Question 9

If there is some form of transition in the communities of plants and animals, what sampling method is more appropriate?

Answer 9

Systematic sampling

Question 10

Describe a line transect

Answer 10

A length of string or tape stretched across the ground in a straight line. Any organism over which the line passes is recorded

Question 11

Describe a belt transect

Answer 11

A strip, usually around a metre wide, marked by putting a second line parallel to the first. The species occurring within the belt are recorded

Question 12

Random sampling with Quadrats and counting along transepts are used to obtain measures of what kind?

Answer 12

Abundance

Question 13

What are the 2 ways in which abundance can be measured?

Answer 13

Frequency and percentage cover

Question 14

To estimate the abundance of animals, what is the most appropriate method?

Answer 14

Mark-release-recapture techniques

Question 15

Why is the mark-release-recapture technique a more appropriate method of measuring abundance in animals?

Answer 15

Most animals are mobile and move away when approached

Question 16

Describe the mark-release-recapture method of measuring abundance

Answer 16

A known number of animals are caught, marked in some way, and then released back into the community. Some time later, a given number of individuals are collected randomly and the number of marked individuals is recorded.

Question 17

What is the Lincoln index?

Answer 17

A calculation used to estimate population size from the mark-release-recapture method

Question 18

Name some of the assumptions that the mark-release-recapture technique relies on

Answer 18

The marked individuals released from the first sample distribute themselves amongst the rest of the population, There are few births or deaths, The mark is not lost

Question 19

Name 3 ethical considerations when investigating populations

Answer 19

Organisms that are removed from their habitat must be returned, Disturbance and damage to the habitat should be avoided, If organisms must be removed from a habitat then numbers taken should be kept to a minimum