What is the definition of population?
A group of sexually interbreeding or potentially interbreeding individuals
What is the definition of species?
A group of interbreeding or potentially interbreeding natural populations, which are reproductively isolated from other such groups
What are metapopulations?
- Occur in fragmented habitats
- Connected by limited migration
- Characterised by extinction and recolonisation: populations are transient
If environmental conditions are good then species will move out to sink populations but if conditions are bad they move back to source populations
Why are populations studied?
- Aids conservation e.g. endangered species Red List - survey regarding the number of individuals in a particular species - mammal based
- Aids management e.g. fisheries
- Determine characteristics:
i) Population distribution/dispersion (size, shape and location that populations occupy)
ii) Density (number per unit area) -> abundance
What is population distribution (i)?
- All individuals -> distribution = geological range
- Environmental conditions
- ## Variable - Metapopulation / Local subpopulation
What is a uniform distribution?
Caused by territories - trying to get as far away as possible within a limited area
What is a clumped distribution?
Depends on life history - bachelor / female groups (herds) - asexually produced organisms
What is a random distribution?
Can’t explain what is happening? Maybe movement / don’t know enough about the environment
What is distribution a measure of?
Dispersion
What is population density (ii)?
- Determining abundance - Abundance = density x area
How can individuals be counted?
- Not possible
- Can’t be sure all have been counted
- Take samples and generalise - gives estimates - use quadrats - extrapolate - gives estimate of density
- Samples vary
- Distribution effects how varied the samples are
- Mark / recapture can be used to study mobile species - tagging, marking, different individuals
What is the Lincoln/Lincoln-Peterson index for measuring density?
N = nM/R N = Population M = Number captured (pre-marking) R = Number recaptured (marked)
What are species limited by?
Adaptations depending on abiotic and biotic factors / range is variable depending on climate conditions
What are population dynamics?
It is a flux:
- Add individuals (birth, immigration)
- Remove individuals (death, emigration)
What are the 2 types of population dynamics?
- Spatial
2. Temporal
What is spatial dynamics?
- Dispersal
- E.g. In less than 60 years Eurasian collared doves expanded their range to the furthest corners of Europe
- Eurasian collared doves began to spread out of Turkey into Europe early in the 20th century
What is temporal dynamics?
Age structure
What are patterns of survival?
- Survivorship curve (see graph)
- High survival among the young e.g. Dall sheep
- High mortality among the young e.g. Mackerel
- 3 types of survivorship curve (see graph)
