SPECIATION, INVESTIGATING POPULATIONS & SUCCESSION

Question 1

Describe what is meant by speciation (allopatric)Describe what is meant by speciation (allopatric)

Answer 1

· Geographical isolation;

· Separate gene pools / no interbreeding (between populations);

· Variation due to mutation;

· Different environmental/abiotic/biotic conditions / selection pressures;

· Selection for different/advantageous, features/characteristics/mutation/ /allele;

· Differential reproductive success / (selected) organisms survive and reproduce;

· Leads to change in allelic frequencies;

· Cannot breed/mate to produce fertile offspring.

Question 2

Describe what is meant by speciation (sympatric)

Answer 2

· NOT Geographical isolation;

· Leads to reproductive isolation

· Separate gene pools / no interbreeding (between populations);

· Selection for different/advantageous, features/characteristics/mutation/ /allele;

· Differential reproductive success / (selected) organisms survive and reproduce;

· Leads to change in allelic frequencies;

Cannot breed/mate to produce fertile offspring.

Question 3

Describe how bacteria can become resistant to antibiotics

Answer 3

· Variation/variety;

· Mutation;

· Some plants have allele to survive/grow/live in high concentration of copper/polluted soils;

· (Differential) reproductive success / adapted organisms reproduce;

· Increase in frequency of allele;

· No interbreeding (with other populations) / separate gene pool / gene pool differs (from other populations);

Question 4

Describe the process of succession

Answer 4

· (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;

Question 5

Describe random sampling

[estimation of population density]

Answer 5

· Use a grid / split area into squares/sections;

· Method of obtaining random coordinates / numbers, e.g. calculator/computer/random numbers table/random number generator;

· Count number/frequency of plants in a quadrat;

· Large sample (20+ quadrats) AND Calculate mean/average number (per quadrat/section);

· Valid method of calculating total number of ……… e.g. mean number of plants per quadrat/section/m2 multiplied by number of quadrats/sections/m2 in wood;

Question 6

Describe systematic sampling

Answer 6

· Transect/lay line/tape measure (from one side of the dune to the other);

· Place quadrats at regular intervals along the line;

· Count plants/percentage cover/abundance scale (in quadrats) OR Count plants and record where they touch line/transect;

Question 7

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

Answer 7

· Method of randomly determining position (of quadrats) e.g. random numbers table/generator;

· Large number/sample of quadrats; (min 20)

· Divide total percentage by number of quadrats/samples/readings;

Question 8

Describe the mark, release, recapture technique

Answer 8

· Capture sample, mark and release;

· Appropriate method of marking suggested / method of marking does not harm fish;

· Take second sample and count marked organisms;

· No in No in Population =

No in sample1 × No in sample2
_________________________________
Number marked in sample2;

Question 9

Describe how you would determine how many quadrats to use when investigating a habitat.

Answer 9

· Calculate running mean/description of running mean;

· When enough quadrats, this shows little change/levels out (if plotted as a graph);

· Enough to carry out a statistical test;

· A large number to make sure results are reliable;

· Need to make sure work can be carried out in the time available;