Hardy / Populations Flashcards
Five Conditions for Equilibrium
- Large breeding population
- Random mating
- No change in frequency due to mutations
- No immigration for emigration
- No natural selection
Causes of Gene Pool Change
- Mutation (DNA change)
- Gene Flow (Migration of alleles)
- Non-Random Mating (self fertilization)
- Genetic Drift (change in allele frequency’s)
- Natural Selection ( selects favourable variations)
Mutations
Created by mutagens or mistakes
Can provide genetic diversity in a species
Gene Flow
Movement of Genes between different populations via migration
Non Random Mating
Uncommon in natural populations
Mates usually selected based on appearance and health
Genetic Drift
Few individuals from a population start a new population with a different allele frequency than the original population
Natural Selection
Acts on mutations by selecting for most successful individual who had the mutations.
Leads to evolution
Census
Counting total in a small area
Sampling
Representatively sample small area and multiply by total area
Open populations
all four factors are functioning
birth,death,immigration,emigration
Closed Populations
No migration
Biotic Potential
four factors
- Max number of offspring
- Chance offspring will reach reproductive age
- Number of times organism reproduces per year
- Age at which reproduction begins
R
Capacity for reproduction
Carrying Capacity (k)
Ability for environment to support a population
Density Dependent factors
Biotic
Limit reproduction as population increases (disease or predation)
Density Independent Factors
Abiotic
Work regardless of population size (floods or drought)
Environmental Resistance
Environmental conditions limit a species from growing out of control - influenced by biotic and abiotic factors
biotic - predators
abiotic- size of land
J Curves
Demonstrate exponential growth
Usually occur in closed populations
S Curves
Most natural populations demonstrate this curve.
Population increases until limiting. factors cause it to reach carrying capacity.
Density factors factors may initiate death phase
K Selected Strategies
Slow Reproduction
Long Life Span
Later reproductive maturity
R Selected Strategies
Rapid Reproduction
Short Life Span
Early reproductive age
Survivorship Curves
Type 1
Large mammals
Few offspring
Low infant mortality
ex Humans
Survivorship Curves
Type 2
Chances of death are about equal throughout life span
ex Squirrels
Survivorship Curves
Type 3
Low survivorship rates in early life
ex Oysters
