7547503
Description
Mind Map by Jacob Shepherd, updated more than 1 year ago
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Created by Jacob Shepherd
about 8 years ago
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Pack 21 -
Population and
Evolution
- Population
- A population is is a group of organisms of the
same species occupying a particular space at a
particular time that can interbreed
- A gene pool is all the
individuals in a
population at a given
time
- Allele frequency =
number of times an
allele occurs within the
gene pool
- The
Hardy-Weinberg
Principle
- The proportion of
dominant and recessive
alleles of a gene will
remain constant from
one generation to the
next
- 5
assumptions:
- No mutations occur
- Isolated population
- No selection
- Large population
- Random
mating
- No mutations occur
- p + q = 1
- p = probability of
dominant allele
- q = probability of
recessive allele
- p = probability of
dominant allele
- p^2 + 2pq + q^2 = 1
- p^2 = frequency of
AA
- 2pq = frequency of Aa
- q^2 = frequency of aa
- p^2 = frequency of
AA
- The proportion of
dominant and recessive
alleles of a gene will
remain constant from
one generation to the
next
- A population is is a group of organisms of the
same species occupying a particular space at a
particular time that can interbreed
- Evolution
- Variation
- Individuals within a population
show a wide range of variation in
phenotype
- Genetic and
environmental factors
cause variation
- Genetic and
environmental factors
cause variation
- Primary source is
mutations
- Also caused by
random
fertilisation
- Types of
variation:
- Discontinuous:
- Organisms fit into few distinct
forms with no intermediate
types
- Organisms fit into few distinct
forms with no intermediate
types
- Continuous:
- Organisms with many
intermediate types
- Organisms with many
intermediate types
- Discontinuous:
- Individuals within a population
show a wide range of variation in
phenotype
- Natural Selection
- Caused by competition,
predation and disease
- A biotic factor is any living component that
affects the population of another organism
or the environment
- Competition:
- Intraspecific: Competition
between organisms of the
same species
- Interspecific: Competition
between organisms of different
species
- Intraspecific: Competition
between organisms of the
same species
- Types of
Selection:
- Stabilising
Selection:
- This occurs when the
environment remains
constant for a long period of
time
- It selects against the extremes
of the phenotypes
- This occurs when the
environment remains
constant for a long period of
time
- Directional Selection:
- Occurs when the environment changes
and so the selection pressure will be to
select for individuals either to the right or
the left of the mean
- Occurs when the environment changes
and so the selection pressure will be to
select for individuals either to the right or
the left of the mean
- Disruptive Selection:
- This occurs when the environment has two or
more distinct forms and so the selection
pressure will be to select for individuals away
from the mean
- It selects for both extremes
- It selects for both extremes
- This occurs when the environment has two or
more distinct forms and so the selection
pressure will be to select for individuals away
from the mean
- Stabilising
Selection:
- Caused by competition,
predation and disease
- A change in allele
frequency of a population
- Main
stages:
- 1) Mutation
- 2)
Variation
- 3) Struggle for existence (selection pressure)
- 4) Survival of the fittest (advantageous allele
survives)
- 5) Reproduction of advantageous
allele
- 6) Natural selection (frequency of allele increases)
- 6) Natural selection (frequency of allele increases)
- 5) Reproduction of advantageous
allele
- 4) Survival of the fittest (advantageous allele
survives)
- 3) Struggle for existence (selection pressure)
- 2)
Variation
- 1) Mutation
- Variation
- Isolation and
Speciation
- If a population becomes
isolated, there will be no
gene flow
- So there is an accumulation
of genetic differences
- These genetic
differences may
eventually lead to
different species
- The isolated populations
cannot interbreed with each
other to produce fertile
offspring
- The isolated populations
cannot interbreed with each
other to produce fertile
offspring
- These genetic
differences may
eventually lead to
different species
- So there is an accumulation
of genetic differences
- Speciation is the evolution of
a new species from existing
ones
- Types of
Speciation
- Allopatric
- Speciation that occurs when
biological populations of the same
species become isolated from each
other preventing interbreeding
- e.g. a river
- e.g. a river
- Speciation that occurs when
biological populations of the same
species become isolated from each
other preventing interbreeding
- Sympatric
- Speciation that occurs
without any
geographical
seperation
- Speciation that occurs
without any
geographical
seperation
- Allopatric
- If a population becomes
isolated, there will be no
gene flow
- Genetic Drift
- Genetic drift is a change in
the allele frequency in a small
population due to chance
- Genetic drift is a change in
the allele frequency in a small
population due to chance
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