methods of sampling/maths

Question 1

When would you
use random
sampling?

Answer 1

when there is a uniform
distribution of the plant species
to avoid bias

Question 2

Quadrat

Answer 2

a frame
gridded or opened
used to sample non-motile
organisms
Competition between members
of the same species

Question 3

What must you do
to ensure your
samples are
representative?

Answer 3

Take a large sample (at least
30)
randomly sample

Question 4

Belt transect

Answer 4

• one tape measure is placed
  through an ecosystem that is
  not uniform
• the quadrat is placed at every
  position along a tape measure

Question 5

When would you
use a line
transect

Answer 5

When sampling a non-uniform
area
e.g. a rocky shore

Question 6

Interrupted belt
transect

Answer 6

• one tape measure is placed
  through an ecosystem that is
  not uniform
• the quadrat is placed at set
  intervals along the tape
  measure

Question 7

The 3 measurements
you can take when
counting plants in a
quadrat?

Answer 7

• density
• percentage cover
• frequency

Question 8

Density
measurement

Answer 8

when you count the individuals
present

Question 9

Frequency
measurement

Answer 9

count how many squares out of
the 100 contain the species you
are investigating

Question 10

Percentage cover
measurement

Answer 10

• investigator estimates the
  percentage of the entire quadrat
  covered with the species that is
  being investigated
• standardise by counting 1% for
  every small square that is at
  least half covered by the plant

Question 11

When would you
use mark-release-
recapture?

Answer 11

Estimate the population size of
motile organisms

Question 12

How would you
randomly sample?

Answer 12

place two tape measures at
right angles to create a gridded
area
use a random number generator
to get coordinates
place the quadrate at the
coordinates and collect the data
repeat at least 30 times

Question 13

How would you
sample using a
line transect?

Answer 13

Place a tape measure at a right
angle to the
road/river/shoreline
place quadrat every set
distance meters (e.g. 5 metres)
collect the data in each quadrat
repeat placing the tape
measure in parallel 30 times

Question 14

What is the formula to
calculate population
size with mark-release-
recapture?

Answer 14

estimated total population = number of organisms initially caught x number of organisms caught in the second sample /number of marked organisms recaptured

Question 15

Describe the mark-
release-recapture
method of sampling

Answer 15

an initial sample of the
population is captured
individuals are marked and
released
allow them time to randomly
disperse
a second sample is captured
the total number captured in
the second sample and the
number recaptured with the
marking are recorded

Question 16

Assumptions of the
Hardy-Weinberg
principle

Answer 16

There will be no change in the allele
frequency between generations
within a population
Assumes:
Large population size
Random mating
No mutations
No selection
No migration (gene flow)