Investigating Populations + Succession

Question 1

What is a species?

Answer 1

A species is a group of closely related individuals, which are capable of interbreeding and producing fertile offspring.

Question 2

What is a population?

Answer 2

A population is all the individuals of a given species living together in the same area at the same time.

Question 3

What is carrying capacity?

Answer 3

Carrying capacity is the maximum, equilibrium number of organisms of a particular species that can be supported indefinitely in each stable environment. Birth rates and death rates are in equilibrium.

Question 4

What is a community?

Answer 4

A community is all the individuals of all the species living together in the same area at the same time.

Question 5

What is a habitat?

Answer 5

Habitat is the place where an organism lives within an ecosystem.

Question 6

What is a niche?

Answer 6

A niche describes where an organism lives and what it does (its role). This includes what it feeds on and how it interacts with other organisms and the environment.

Question 7

Can several organisms occupy the same habitat?

Answer 7

Yes, several organisms may be found in the same habitat but will occupy a different niche.

Question 8

Define the competitive exclusion principle

Answer 8

Two species do not have the same niche as different niches reduce competition between them, so ensures both species survive.

Question 9

What is interspecific competition?

Answer 9

Competition for resources between organisms of different species

Question 10

What is intraspecific competition?

Answer 10

Competition for resources between individuals of the same species

Question 11

Estimating population sizes/abundance?

Answer 11

1) Use a grid
2) Use a random number generator to obtain random coordinates and place quadrats on each random coordinate
3) Count number of named species or frequency (% cover) in quadrat
4) Calculate running mean

Question 12

How many quadrats should be used in a sample?

Answer 12

1) Calculate running mean
2) Stop sampling when there is little change
3) Enough to carry out a statistical test
4) A large number to make sure the mean is reliable

Question 13

Systematic sampling? Changes across an area.

Answer 13

1) Transect
2) Place quadrats at regular intervals along the line
3) Count species/% cover in quadrats

Question 14

Equation for calculating estimated population size?

Answer 14

N1 × N2 ÷ Nm

N1 - number caught the first time
N2 - number caught the second time
Nm - number caught the second time, which were marked

Question 15

Mark-Release-Recapture method?

Answer 15

1) Capture sample, mark and release
2) Ensure method of marking does not harm the organism
3) Allow organism to redistribute back into the population
4) Take second sample and count marked organisms
5) No population = N1 × N2 ÷ Nm

Question 16

Why should species not be removed from the position they originate?

Answer 16

If they are removed, it will cause distress

Question 17

Why should the species be returned to the same spot if possible (even if they’re dead)?

Answer 17

Their absence causes distress to their family/friends

Question 18

Why should there be minimal damage to the organisms habitat?

Answer 18

Could change abiotic/biotic factors and therefore change the ecosystem

Question 19

Why should sites not be overused and be given time to recover?

Answer 19

Animals become aware of traps, take advantage of them, or avoid them.

Question 20

Why should marking not be brightly coloured?

Answer 20

Individual is more susceptible to predation.

Question 21

Biotic factors?

Answer 21

Competition between organisms, disease, predation

Question 22

Abiotic factors?

Answer 22

Temperature, light intensity, wind speed, water + soil pH, salinity, water level in soil, slope of the land

Question 23

Describe the process of succession?

Answer 23

1) Colonisation by named pioneer species
2) Pioneers cause change in environmental abiotic / biotic factors e.g soil pH
3) Pioneers make the environment less hostile for new species
4) New species make conditions less suitable for previous species
5) Change in biodiversity
6) Stability increases
7) Climax community
8) Occurs over a long time

Question 24

What are features of a climax community?

Answer 24

Stable community
Same species present over a long time

Question 25

When does secondary succession occur?

Answer 25

After a forest fire, clearance of agricultural land (e.g flood). However, there may be spores/seeds still viable in the soil so therefore succession occurs with a species from an intermediate seres.

Question 26

Define deflective succession?

Answer 26

A climax community is prevented from establishing.

Due to e.g management practises by humans (sheep grazing)