INVESTIGATION

Question 1

We can measure the biotic factors in 5 ways

Answer 1

Abundance of population: counting the number of organisms in the sample
Richness of population: number of different species found in a sample
Diversity of population: Simpson Diversity index which takes into account the richness and abundance
Growth of population: comparison of growth with between species
Biomass of population: used when studying productivity of an organism

Question 2

Abundance of the population

Answer 2

Frequency: the likelihood of the species occurring in a quadrat
Percentage Cover: Estimate of the area within a quadrat that a species covers

Question 3

How Percentage Cover of an organism of an area may be measured

Answer 3

Use of quadrats that are randomly placed
Use a large number of quadrats so as to reduce sampling error
Estimate percentage of area covered by organism (by counting all the squares occupies by the species)

Question 4

Why Percentage Cover is better to use than Frequency

Answer 4

Frequency is too large

Plants are too small

Question 5

How you would decide the number of quadrats to use

Answer 5

Take enough to carry out a statistical test
Take into consideration the amount of time you have to carry out the investigation
Take a large enough number to make results reliable
Ensure unnecessary extra quadrats are not placed

Question 6

What size the quadrat should be

Answer 6

Depends on size of animal
If a species occurs in a series of groups in an area, then use a large number of small quadrats to give representative data

Question 7

Purpose of a Chi-Squared test

Answer 7

To compare different numbers collected from the two sites and show whether the differences are significant enough to confirm or reject the null hypothesis

Question 8

RANDOM SAMPLING

Answer 8

Divide study area into grid of numbered line
Using random numbers, from a table or generated by computer, obtain a series of coordinates
Take samples at the intersection of each coordinates of number of individuals and number of species
Repeat many times and take a mean

Question 9

How Mark-Release-Recapture can be used to estimate the number of a population that is MOBILE

Answer 9

Capture sample, mark and release
The harming must not harm the animal, (mention method of marking)
Take second sample and count marked organisms
Use the LINCOLN INDEX which is (Number in sample 1 x Number in sample 2) ÷ Number marked in sample 2

Question 10

Things to ensure when using Mark-Release-Recapture

Answer 10

Animals are not harmed
Animals must not be made less mobile or more visible to predators due to the mark; one way to do this is to mark the animal using an ultra-violet marking pen which can only be seen under ultra-violet light
Leave enough time for the marked individuals to redistribute themselves and mix with the population
Ensure it is not breeding season of the animal, as breeding season increases the population size
The mark must not be rubbed of or lost during investigation
The population has a definite boundary so there is no migration
The proportion of marked to unmarked in second sample is the same as the proportion of this in whole population
Sampling method is the same

Question 11

Why population size may change during a year

Answer 11

Breeding
Availability of food source
Predator presence
Variation in disease
Temperature variation
Availability of water

Question 12

Precautions and ethical considerations when doing field work

Answer 12

Only work in places where risk of falling in water is small
Only work in places where risk of pollution is small
Ensure cuts and broken skin are covered
Ensure all participants wash hands afterwards
Ensure not to disrupt the food chain of the environment

Question 13

Predation can help other species

Answer 13

Predator eats a specific species

The other species has less competition and therefore can now increase percentage survival rate

Question 14

Although predators reduce population size of prey, they actually increase mean mass of prey

Answer 14

Predators kill prey therefore reducing prey population size
Therefore less competition between prey population
More food available
Therefore more food eaten by a single prey than would be eaten before presence of predator
Therefore preys may be small in number but each one will be fatter than usual

Question 15

Population Growth

Answer 15

Lag Phase; small number of individuals reproduce slowly
Rapid Growth Phase; increasing number of individuals reproducing
Stable Phase; population GROWTH declines and population size remains stable
Carrying Capacity is established
(Births + Immigration)-(deaths + emigration)

Question 16

Percentage Growth Rate

Answer 16

(Population change during period x 100) ÷ Population at start of period

Question 17

Birth Rate

Answer 17

(Number of births per year x 1000) ÷ Total population that year

Question 18

Death Rate

Answer 18

(Number of deaths per year x 1000) ÷ Total population that year

Question 19

Average Life Expectancy

Answer 19

age at which 50% of the population in the sample used are still alive

Question 20

Demographic Transition

Answer 20

Change in the population structure

e.g. Increase in average life expectancy, lower death rates, higher birth rates