Investigating Populations & Succession

Question 1

Define the term Species

Answer 1

• A group of closely related organisms
• Reproduce to produce fertile offspring

Question 2

Define the term population

Answer 2

• All the individuals of a given species living together in the same area at the same time

Question 3

Define the term Carrying Capacity

Answer 3

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

Question 4

Define Community

Answer 4

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

Question 5

Define the habitat

Answer 5

• place where organism lives within an ecosystem

Question 6

Define the term Niche

Answer 6

• An organisms role within a community
• describes how an organism interacts with other organisms and how it responds to the environment

Question 7

Describe the difference between Interspecific and Intraspecific competition

Answer 7

• Interspecific: competition with different species
• Intraspecifc: competition within a species

Question 8

What do you have to ensure when estimating?

Answer 8

• To avoid bias the samples must be selected at random
• To ensure data is reliable and representative: large enough sample must be taken and when running mean shows little difference then there is enough samples
• method of collection of samples must be appropriate to the species

Question 9

Describe Random Sampling

Answer 9

• Use a grid/ split area into sections
• Method of obtaining random coordinates e.g random number generator
• Count number of plants in a quadrat
• Calculate average number per quadrat
• valid method of calculating total number of plants

Question 10

How many quadrats should you use in the sample?

Answer 10

• calculate running mean
• stop sampling when there is little change
• enough to carry out statistical test
• a large number to make sure mean is reliable
• need to make sure work can be carried out in the time available

Question 11

Describe systematic sampling

Answer 11

• Transect from one side of dune to the other
• Place quadrats at regular intervals along the line
• count plants and record where they touch the line

Question 12

What is a transect?

Answer 12

• recording what species are touching the line at each sampling point

Question 13

What is a belt transect?

Answer 13

• placing two parallel lines across, a metre apart and recording what species are found between the lines

Question 14

What is an interrupted belt transect?

Answer 14

• using one line and placing a quadrat down at equally spaces sampling points & recording abundance of species within quadrat

Question 15

Describe the mark, release, recapture technique

Answer 15

• capture sample, mark and release
• appropriate method of marking suggested (no harm)
• take second sample & count marked organisms
• no in no population =
  no in sample 1 x no in sample 2/ number marked in sample 2

Question 16

Define the term pioneer species

Answer 16

• the organisms that first colonise an area

Question 17

Define the term sere

Answer 17

• complete succession from pioneer community to climax community
• seral stage is a particular stage in this succession with its own distinctive community of organisms

Question 18

Define the term climax community

Answer 18

• • final stage of ecological succession
• is stable and changes very little
• type of community formed depends to a large extent on the climate

Question 19

Define the term hostillity

Answer 19

• hostile environments: diversity is low & abiotic factors dominate the distribution of species
• less hostile environments: diversity is high & biotic factors dominate the distribution of an abundance of organisms

Question 20

Define the term diversity

Answer 20

• relationship between number of individual organisms & number of species within a community
• high diversity: stable ecosystem, complex food webs, if population of one species drops then others will be able to increase numbers to fill in niche, so community is not affected
• low diversity: unstable eco system, less complex food webs, if one species dies then whole ecosystem may be disrupted

Question 21

Describe the process of succession

Answer 21

• colonisation by pioneer species
• change in environment
• enables other species to colonise
• change in biodiversity
• stability increases
• climax community

Question 22

Describe how bacteria can become resistant to antibiotics

Answer 22

• variation
• mutation
• some plants have allele to survive
• differential reproductive success
• increase in frequency of allele
• no interbreeding

Question 23

Describe how you would determine the mean percentage cover for beach grass on a sand dune

Answer 23

• method of randomly determining position of quadrats e.g random number generator
• large sample of quadrats
• divide total percentage by number of quadrats