Investigating Populations and Succession

Question 1

What is meant by carrying capacity

Answer 1

The maximum number of organisms a particular species that can be supported indefinitely in each stable environment

Question 2

What us the difference between interspecific and intraspecific competition

Answer 2

Interspecifc conpetition is the competition for resources between organisms of different species
Intraspecific competition is competition between individuals of the same species

Question 3

Why cant 2 species occupy the same niche

Answer 3

Different niches reduce competition between the 2 species eg food and shelter
So both species can survive
This is called competitive exclusion

Question 4

What is a biotic factor and give 3 examples

Answer 4

Living factor which affects the distribution of an organism
E.g Pathogens , Predators , Competition between organisms (inter/intraspecific)

Question 5

What is an abiotic factor and give 3 examples

Answer 5

Non living factor which affects the distribution of organisms
Eg. climatic factors such as temp, LI and wind speed , Salinity of water, Longitude Latitude and Altitude

Question 6

What happens when 2 niches ocerlap

Answer 6

The better adapted species will outcompete the other species and eliminate them

Question 7

What must you ensure when carrying out sampling techniques

Answer 7

1.Ensure the dataa collected is not biased and selected at random
2. The data is reliable and representative and suitable for statistical analysis
3. A large number of samples more than 20 in order to find where the running mean stablises
4. The method must be appropriate to the species e.g. Quadrating suitable for slow moving organisms

Question 8

What is a quadrat

Answer 8

A frame of known area which is placed on the ground to estimate a population size

Question 9

How can the abundance of species be measured within a quadrat

Answer 9

Through density, Percentage cover or Frequency

Question 10

How is density measured in a quadrat
what are strengths and limitations to this

Answer 10

By counting all individuals present and calculate density
Species May be difficult to count
Time consuming
Most accurate

Question 11

How is Frequency measured in a quadrat
what are limitations to this

Answer 11

Count number of quadrats which contain species and calculate average frequency per metre squared (proportion of quadrats that contain the sepcies)
Least accurate

Question 12

How is %cover measured in a quadrat
what are strengths and limitations to this

Answer 12

Total area covered by species/Total area of quadrats x100
used when there are too many individuals to count

Question 13

what is the method of random quadrating

Answer 13

1. Map the area with 2 measuring tapes at a right angle to form the axis of a grid
2. Use a random number generator to obtain a series of random co ordinates
3. Place a quadrat in the intersection of these co ordinates
4. Abundance can be measured by frequency/density/%cover

Question 14

Describe how you would investigate the distribution of marram grass from onr side of the dune to the other

Answer 14

1. Place a transect across the area
2. Place quadrats at regular intervals
3. Count plants/Percentage cover/abundace in quadrats

Question 15

Descrube the method of mark release recapture

Answer 15

1. Ethically collect animal species by usually using netting ot trap technique and count
2. Then mark in a way that does not affect abillity to feed or increase predation
3. Release and leace to redistribute to population
4. After reasonable amount if time carry out a second capture and count t he total number caught and the number previously marked

Question 16

How do you work out population size from a mark release recapture

Answer 16

Number caught first time x Number caught second time / Number caught second time which were marked

Question 17

What is a pioneer species

Answer 17

The organisms that first colonise an area e.g. marram grass in a sand dune ecosystem

Question 18

What is a sere

Answer 18

The complete succession from pioneer community to climax community

Question 19

What is a climax community and what are 2 features

Answer 19

The final stage of ecological succession.
A stable community that has very little change.
Complex food web

Question 20

Descrube and explain how succession occurs

Answer 20

•(Colonisation by) pioneer species;
• Pioneers cause change in environmental abiotic / biotic factors(give an example);
• Pioneers make the environment less hostile for new species;
• New species change/make conditions less suitable for previous species;
• Change/increase in diversity/biodiversity;
• Stability increases [population/richness/abiotic factors];
• Climax community;