Population Genetics Flashcards
What is allele frequency?
The proportion of gene copies of a given allele in a population
What is a fixed frequency?
When only a single allele is present for a gene (that allele frequency is 100%)
What are the equations for the Hardy-Weinburg Principle?
p + q = 1 (for allele frequencies)
p^2 + 2pq + q^2 = 1
What are the conditions of the Hardy-Weinburg Principle?
The population is infinitely large
No migration occurs
No mutation occurs
No natural selection occurs
Mating is random
What is genetic drift?
Is the change in the genetic makeup of a population from chance
What is the founder effect?
When individuals from a large population leave to establish a new population the resulting genetic drift is called the founder effect
What is the bottleneck effect?
When a random, severe environmental event results in a drastic reduction in population size (and genetic drift) it is known as the bottleneck effect
What is gene flow?
The movement of alleles from one population to another through the movement of individuals or gametes
When individuals migrate they alter the gene pool of both populations
How do mutations effect the genetics of a population?
When a mutation arises, it has the potential to alter the gene pool or allele frequencies of the population, and therefore the Hardy-Weinberg Equilibrium
How does natural selection effect the genetics of a population?
Mutations may result in a new phenotype
Natural selection then acts upon the mutation
Mutation provides a source of variation, but natural selection acts on individuals and their phenotypes, and causes changes over time
How do you calculate the density of a population?
Population density (Dp) is the number of individual organisms (N) in a given area (A) or volume (V)
Dp = N/A Dp = N/V
What are distribution patterns?
Population dispersion refers to the general pattern in which individuals are distributed through a specific area
Clumped dispersion, uniform dispersion, random dispersion
How do you calculate changes in population numbers?
There are 4 processes that change the size of a population
Mortality (Deaths) (m)
Emigration (e)
Natality (Births) (n)
Immigration (i)
N = (n + i) - (m + e)
What is growth rate?
Growth rate (gr) is the change in population size per unit of time
Per captia growth rate (cgr) is the change in population size relative to initial size of population per unit of time
gr = N/t
cgr = Nf - Ni/N
What is biotic potential?
Is the maximum number of offspring that can be produced when there are no restrictions
An organism reaches its biotic potential when there is unlimited resources (food, water, shelter, etc) and ideal living condition
What factors effect biotic potential?
Number of offspring per cycle
How many offspring live long enough to reproduce
Age of reproductive maturity
How often they reproduce in one life span
The length of the life span
What is exponential growth (J shaped curve)?
Exponential growth demonstrates growth limited only by biotic potential
Usually small organisms
What is the lag phase?
At the beginning the population is small so growth of this population is slow, as the numbers increase the population will experience an exponential rate of growth
What is carrying capacity?
The limit to the number of individuals that an environment can support at any given time
Carrying capacity = max number
What is a logistic growth pattern (S shaped sigmoidal curve)?
Eventually, competition for resources will slow the rate of growth
Logistic growth, limited by carrying capacity, is most like the population growth seen in wild populations
What is a K-Selected Species?
Have few offspring per cycle, offspring take a long time to mature, they live a long time and are usually larger in size
Their numbers stay close to the carrying capacity
They display an S-shaped logistic graph
What is a R-Selected Species?
Organisms that have a high potential, like insects
Short life span, early reproductive age, produce lots of offspring
Their populations spike and then have a drastic drop
They display a exponential, J-Shaped curve
What are density dependent factors?
A factor that influences a population at a particular density
Intraspecific competition, predation, disease
What is a minimum viable population?
The smallest number of individuals needed for a population to continue
What are density independent factors?
A factor that has the same influence on a population at any population density
Habitat destruction, natural disasters, human action
What are Limiting Factors?
Of all the resources that a population requires for growth, the resource in the shortest supply is called the limiting factor and it determines how much the population can grow
Can be density dependent or density independent
What is interspecific competition?
Competition between individuals of different species
What is interference competition?
Actual fighting or aggression between individuals of different species over the same resource
What is Exploitative Competition?
Consumption of shared resources, one species monopolizes the resources
What is succession?
Is the slow, progressive replacement of one community by another during development of vegetation in the area
What is primary succession?
Plant life in area not previously covered by vegetation
What is secondary succession?
Succession in an area that did have vegetation and still has some soil
What is a pioneer community?
The first species to appear during succession