topic 4C - sampling, stats

Question 1

what is sampling?

Answer 1

is a method of investigating the abundance and distribution of species and populations

Question 2

two different types of sampling:

Answer 2

-random
-systematic

Question 3

what is random sampling?

Answer 3

the positions of the sampling points are completely random/due to chance

Question 4

advantage of random sampling:

Answer 4

no bias by the person that is carrying out the sampling

Question 5

what is systematic sampling?

Answer 5

-the sampling points are chosen by the person carrying out the sampling
-the quadrants are spaced regularly

Question 6

disadvantages of random sampling:

Answer 6

-the person choosing could show bias towards or against certain areas
-this is unrepresentative of the whole area

Question 7

what is sampling often used to estimate?

Answer 7

-distribution
-abundance

Question 8

what is distribution of a species?

Answer 8

how it is spread throughout the ecosystem

Question 9

what is the abundance of a species?

Answer 9

the number of individuals of that species

Question 10

quadrat random sampling steps (population density)

Answer 10

1) convert the sampling area into a grid format

2) use a random number generator to pick the sample points / generate a pair of random coordinates on your grid

3) place the first quadrat on your grid using these coordinates

4) count the number of individuals in the quadrat

5) multiply the mean number of individuals per quadrat by the whole area to calculate the estimated population size

Question 11

what is population density?

Answer 11

the number of individuals per m­­­^2

Question 12

quadrat random sampling steps (percentage cover)

Answer 12

1) use a random number generator to pick the sample points / generate a pair of random coordinates on your grid

2) place the first quadrat using these coordinates (each square of a grid quadrat is equivalent to 1% cover)

3) count the number of squares in each quadrat within which the species occupies over half the square

(if 30 squares contain the species, the percentage cover is 30%)

Question 13

quadrat random sampling steps (abundance)

Answer 13

1) place a frame quadrat at multiple coordinates generated

2) count the number of quadrats that contain the species

(if 3 out of 10 quadrats contain the species the frequency is 30%)

Question 14

what is species frequency?

Answer 14

the probability that the species will be found within any quadrat in the sample area

Question 15

how to calculate species frequency:

Answer 15

number of quadrats that the species was present in / the total number of quadrants

x100

Question 16

what is species density?

Answer 16

how many individuals of that species there are per unit area

Question 17

how to calculate species density:

Answer 17

number of individuals counted across all quadrats / the total area of all the quadrats

(answer = x individuals per unit of quadrat^2)

Question 18

how to calculate percentage cover:

Answer 18

the number of squares the species is found in is equivalent to its percentage cover in that quadrat

(eg: if grass is found in 89 out of 100 squares in the quadrat then it has a percentage cover of 89%)

Question 19

limitations of quadrats:

Answer 19

-can only be used for immobile species
-frequency technique shows how common a species is but it does not give information on the estimated number of individuals or the size of the population

Question 20

advantages of quadrats:

Answer 20

-percentage cover and frequency, when used together, give a good picture of the distribution of a species
-if a species had a high mean percentage cover but a low frequency it would suggest the species lives in groups in preferred areas of the habitat

Question 21

what do quantitative investigations of variation involve?

Answer 21

the interpretation of mean values and their standard deviations

Question 22

what is a mean value?

Answer 22

the average value of a data set

Question 23

what is standard deviation?

Answer 23

a measure of the spread or dispersion of data around the mean

Question 24

what does a small standard deviation indicate?

Answer 24

that the results lie close to the mean (less variation)

Question 25

what does a large standard deviation indicate?

Answer 25

indicates that the results are more spread out

Question 26

what does an overlap in standard deviation suggest?

Answer 26

the results are not significantly different

Question 27

what does no overlap in standard deviation suggest?

Answer 27

the results are significantly different

Question 28

TIP FOR STANDARD DEVIATION:

Answer 28

-writing out the range of values for each data set before starting to answer the question
-the standard deviations of a data set can be represented by standard deviation error bars on a graph

Question 29

what is percentage cover?

Answer 29

the percentage of the quadrat area that is covered by one species, used to identify plant frequencies

Question 30

what is a quadrat?

Answer 30

-square frames of wire usually (0.25 m²)
-placed on the ground to look at the plants or slow-moving animals within them

Question 31

sampling with traps

Answer 31

-small animals (like insects) need to be trapped so they can be counted and then released afterwards

-pitfall traps are small traps dug into the ground, often with food inside to attract small mammals

-the sides of these traps are smooth to stop the mammals escaping

Question 32

sweep netting

Answer 32

collecting insects and other organisms by sweeping a net through vegetation

Question 33

kick sampling

Answer 33

-disturb mud and vegetation near a river
bank bed
-hold nets downstream of an area of river
-the small animals float into the net

Question 34

pooters

Answer 34

small devices used when sampling to suck up small insects safely without them going into your mouth

Question 35

transect

Answer 35

a line created along which sampling occurs

Question 36

zonation

Answer 36

growing of plants in distinction regions due to changes

Question 37

zonation

Answer 37

growing of plants in distinction regions due to changes