speciation, investigating populations & succession Flashcards
Describe what is meant by speciation (allopatric)
- 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.
Describe what is meant by speciation (sympatric)
- 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.
Describe how bacteria can become resistant to antibiotics
- 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);
Describe the process of succession
- (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;
Describe random sampling
[estimation of population density]
- 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;
Describe systematic sampling
- 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;
Describe how you would determine the mean percentage cover for beach grass on a sand dune.
- 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;
Describe the mark, release, recapture technique
- 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;
Describe how you would determine how many quadrats to use when investigating a habitat.
- 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;
causes of variation
mutation
meiosis
random fertilisation
species defn
a group of closely related individuals to produce fertile offspring
population defn
a population is all the individuals of a given species living together in the same area at the same time
community defn
a community is all the individuals of all the species living together In the same area at the same time
