Populations Flashcards
Define population
A group of organisms living in the same space at the same time which have the potential to interbreed
What is the gene pool?
All the alleles of all the genes of all the population at any one time
What is the allele frequency of a population?
The number of times an allele occurs within a gene pool
What are the hardy weinberg equations?
P^2 + 2pq + q^2 = 1
P+ q = 1
What assumptions need to be taken when using the hardy Weinberg equations
Large enough sample
Random mating
No selective advantages
No mutations
Give three causes of genetic variation
Mutations
Meiosis - crossing over and independent segregation
Random fertilisation
What is infraspecific competition?
Competition within a species
Describe the steps of natural selection
Mutations create alternate allelles
Greater genetic variation
Selection pressures favour the survival of certain individuals
Selected individuals more likely to reproduce
Next generation have a higher allele frequency of selected allele, some alleles may be selected against to the point of being removed from the gene pool
Describe disruptive selection
Selection favours both extremes
E.g. Fur length
Winter favours long, summer favours short
Mid length never selected for
What is speciation?
Where two populations become separated from each other, meaning natural selection occurs differently in each
Creates new organisms
Describe a genetic bottle neck
Large rapid decrease in a population
Leads to reduction in gene pool
Only some survive
What are the two types of speciation?
Allopatric - two populations are geographically separated, i.e. By flooding, climatic conditions give rise to new species
Sympatric - speciation in the same place, e.g. Different courtship dances or anatomical differences
Define ecosystem
Biotic an abiotic features within a certain area and the interactions between them
Define community
All the populations of all the species within a habitat at one time
Define biological niche,
How an organism fits into the environment i.e. Its relation to biotic and abiotic factors.
No 2 species can fit the same niche when resources are limited
What is a habitats carrying capacity?
The maximum population size maintained by a habitat
What are the two types of transect?
Standard grid
Point quadrat - pins go through top which lead down to plant
What is a belt transect?
Tape measure placed along length of area investigated
Place quadrat every x meters
Give three ways of measuring abundance in an ecosystem
Frequency - number of quadrats that have the species in (good for hard to count organisms)
Percentage cover - % of a quadrat covered by the plant (good for speed)
Simple counting
Describe the mark release recapture technique
Capture and mark a sample of organisms
Release and leave for a suitable time
Recapture them
Calaculate population by: (first sample x second sample) / those recaptured
What assumptions need be made when using mark release recapture
Re- disperse evenly
No births or deaths since 1st capture
Closed habitat
Describe primary succession
Hostile enviroment inhabited by a pioneer species which is heavily adapted to the enviroment e.g. Asexual reproduction, rapid germination photosynthetic, nitrogen fixing
Pioneer species dies, through decomposition it improves soil fertility
Nutrients allow a small community to be supported ( pioneer species reduces hostility)
More decomposition causes more complex organisms to be able to grow
Stable climax community is formed
