Investigating Populations & Succession Flashcards
Describe what is meant by allopatric speciation.
- Geographical isolation
- Separate gene pools / no interbreeding (between populations)
- Variation due to mutation
- Different environmental conditions/selection pressures
- Selection for different/advantageous features/allele
- Differential reproductive success / selected organisms survive and reproduce
- Leads to change in allelic frequencies
- Cannot breed to produce fertile offspring.
Describe what is meant by sympatric speciation.
- NOT Geographical isolation
- Leads to reproductive isolation
- Separate gene pools / no interbreeding (between populations)
- Selection for different/advantageous features/allele
- Differential reproductive success / selected organisms survive and reproduce
- Leads to change in allelic frequencies
- Cannot breed to produce fertile offspring.
Describe how bacteria can become resistant to antibiotics.
- Variation
- Mutation
- Some plants have allele to survive/grow in high concentration of copper/polluted soils
- Differential reproductive success / adapted organisms reproduce
- Increase in allelic frequency
- No interbreeding (with other populations) / separate gene pool
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
- Increase in biodiversity
- Stability increases [population/richness/abiotic factors]
- Climax community
Describe random sampling.
[estimation of population density]
- Use a grid / split area into sections
- Method of obtaining random coordinates, e.g. random number generator
- [Count number/frequency of plants in a quadrat
- Large sample (20+ quadrats) AND Calculate mean/average number (per quadrat)
- Valid method of calculating total number of ……… e.g. mean number of plants per quadrat/m2 multiplied by number of quadrats/m2 in wood]
Describe systematic sampling.
- Transect measure (from one side of the dune to the other)
- Place quadrats at regular intervals along the line
- Count plants/percentage cover (in quadrats) OR Count plants and record where they touch 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 number generator
- Large number of quadrats (min 20)
- Divide total percentage by number of quadrats/samples
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 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
When is percentage cover used?
When there are too many too count.
What is a biotic factor?
A living factor which affects the distribution of an organism.
What is an abiotic factor?
A non-living factor which affects the distribution of an organism.
Examples of biotic factors.
- Competition between organisms, predation and disease
- Invasive species
- Human impact
- Algae (eutrophication)
- Presence of Mycorrhizae
Examples of abiotic factors.
- Climatic factors such as temperature, light intensity and wind speed
- Physical factors such as soil / water pH, water level in soil and slope of the land
- Aspect (NESW)
- Altitude
- Turbidity of salinity of water
Why do no two species have exactly the same niche?
‘Competitive Exclusion Principle’ states that when two species compete for exactly the same resources (i.e. they occupy the same niche), one is likely to out-compete the other and be more successful.
