Investigating Populations & Succession

Question 1

Define ecosystem

Answer 1

How a community and its abiotic factors interact in a given area

Question 2

What is a niche?

Answer 2

Describes where an organism lives and its role. (Feeds on, how it interacts with other organisms and the environment)

Question 3

What is a carrying capacity?

Answer 3

The maximum number of individuals in a species that can be supported indefinitely by its environment.

Question 4

Define species

Answer 4

A group of closely related organisms that are capable of interbreeding and producing fertile offspring

Question 5

Define community

Answer 5

All the individuals of all species living together in the same area at the same time

Question 6

Difference between inter-specific and intra-specific competition?

Answer 6

Inter = Competition for resources between organisms of DIFFERENT species

Intra = Competition for resources between organisms of SAME species

Question 7

Why do no 2 species have exactly the same niche?

Answer 7

Different niches reduce competition so ensure both species survive (competitive exclusion principle)

Question 8

What happens when niches overlap?

Answer 8

The better adapted species displaces the second

Question 9

The mark-release-recapture method can be used to estimate the size of a fish population. Explain how. (4)

Answer 9

• Capture sample of fish and mark then release
• Ensure marking is not harmful to fish
• Allow time for fish to randomly distribute back into POPULATION before collecting second sample.
• Population - No. 1 sample x No. 2 sample / No of marked fish in 2nd sample.

Question 10

Suggest why the MRR method can produce unreliable results in very large lakes (2)

Answer 10

-Less chance of recapturing fish/unlikely fish distribute randomly
- Fish may remain in one area

Question 11

Describe how you would determine how many quadrats to use when investigating a habitat (5)

Answer 11

• Calculate running mean
• Running mean levels out when enough quadrats
• Enough samples to carry out a STATISTICAL TEST
• A large number (20 min.) to ensure results RELIABLE and REPRESENTATIVE
• Ensure work can be carried out in time available

Question 12

Describe how you would determine mean percentage cover of grass on a sand dune (3)

Answer 12

• Method of randomly determining quadrat positions (random no. generator)
• Large number of quadrats (min.20)
• DIVIDE TOTAL % BY NO. OF QUADRATS

Question 13

What to do when estimating? (3 points)

Answer 13

• Samples collected RANDOMLY to eliminate BIAS
• Ensure data is RELIABLE and REPRESENTATIVE and suitable for STATISTICAL ANALYSIS (large enough sample taken of more than 20)
• Method of sample collection appropriate to species (quadrat = immobile organisms)

Question 14

Ways of measuring abundance? (3)

Answer 14

• Density
• Percentage cover
• Frequency

Question 15

Density?1

Answer 15

Count of ALL individuals present.
Time consuming. Most accurate.

Question 16

Percentage cover?

Answer 16

Area of quadrat covered by 1 species recorded as % of total area (estimated)
Used when too many individuals to count.

Question 17

Frequency

Answer 17

Proportion of quadrats that contain a particular species (Species found in 40/100 quadrats taken, frequency = 40%). Least accurate.

Question 18

Method for random quadratting? (4)

Answer 18

• Use a grid to split area into sections
• Method of obtaining random coordinates (random no. generator)
• Count no. of plants in quadrat
• Calculate running mean of plants.

Question 19

How many quadrats to use in sample? (5)

Answer 19

• Calculate running mean
• Stop sampling when running mean levels out
• Enough samples to carry out STATISTICAL TEST
• Large number to make sure mean is reliable and representative (20 min.)
• Work able to be carried out in time available

Question 20

What are transects used for?

Answer 20

To know how species abundance varies ACROSS an area rather than what species are present

Question 21

Define interrupted belt transect

Answer 21

Using one line and placing a quadrat down at equally spaced sampling points and recording species abundance within.

Question 22

Examples of abiotic factors

Answer 22

• Temperature
• Light Intensity
• Water availability
  pH of soil

Question 23

Biotic Factors

Answer 23

• Competition
• Predation

Question 24

Define succession

Answer 24

A series of changes within a community. A long process which starts from baron rock to its climax community.

Question 25

Define and explain pioneer species

Answer 25

The organisms that first colonise an area. (E.g: marram grass in a sand dune ecosystem.)

Typical features include asexual reproduction, photosynthesis, rapid germination, and production of vast quantities of wind-dispersed seeds.

Question 26

Define Sere

Answer 26

A complete succession from pioneer community to climax community.

Question 27

Define climax community

Answer 27

The final stage in an ecological succession.

Stable and changes very little. Type of community depends on large extent on abiotic factors.

Question 28

Define hostility

Answer 28

Where an area’s abiotic factors are unfavourable with few species adapted to survive in such conditions.

Low diversity and abiotic factors dominate distribution of species.

Question 29

Define abiotic environment

Answer 29

Non-living parts of environment

Question 30

Define diversity

Answer 30

The relationship between the number of individual organisms and the number of species within a community.

A diverse community will have a wider range of species and a greater number of indivudals present than a less diverse community.

Question 31

Describe and explain how succession works (5)

Answer 31

• Colonisation by pioneer species.
• Environment altered
• This change enables other species to colonise
• Change in diversity
• Stability increases, less hostile environment.
• Climax community represented by named species.