Variation & Evolution Jan 2026
Sources of Variation
Heritable -
> 1) Genetic variation (different alleles
Litabe2) Environmental
3) Epigenetic
variation
differences leading ,
to differences in
gene expression
-
Continuous & Discontinuous variation :
(types of variation
·
Continuous -
phenotypes that show continuous variation
·
Discontinuous variation
>
-
All
organisms in the population fall on a
-
*
For phenotypes showing discontinuous variation ,
continuum between two phenotypic extremes be placed into on e of small
organisms can a
,
>
-
Controlled by the alleles of
many genes (polygenic number of phenotypic groups
Phenotypes showing
* >
these phenotypes 1
-
continuous variation
-
controlled
are are
usually by gene
impacted by the environment (monogenic
>
100 %
-
e g
. genetically controlled no environmental
-
.
frequency -
-
.
7 impact 2
.
g
MM11
.
height
frequency
.
7
blood
group
The benefit
to a population of genetic variation :
mem
If a
population is made up of genetically identical Selective pressure :
the abiotic or biotic environmental
organisms & the environment is stable ,
then the factor that determines the value
whole population can survive .
of an allele (which will lead to
greater
↳ Also this well-adapted
, genome will be passed reproductive success .
=>
on to all offspring. However , no environment is If selective
pressures change the alleles , providing
stable forever When it .
changes ,
none of the organisms a selective advantage or
disadvantage will also change
will be able to tolerate the new conditions >
-
Population
goes extinct 1) Natural selection : alleles that result in an advantageous
phenotype will result in
greater reproductive success
How does variation in a
population change ? These alleles will be passed frequently to
on more
offspring
-
-
Gene Pool all alleles of all genes population & their frequency
in in the population will
:
a . increase
<
pop .
W/ high genetic diversity has a
large gene pool falleles resulting in a
poorly adapted phenotype will become less
Allele frequency : The proportion of organisms in a
frequent)
population that carry particular allele The change allele leads to change in the
-
a in
frequency a
average
phenotype This .
is evolution .
Sources of Variation
Heritable -
> 1) Genetic variation (different alleles
Litabe2) Environmental
3) Epigenetic
variation
differences leading ,
to differences in
gene expression
-
Continuous & Discontinuous variation :
(types of variation
·
Continuous -
phenotypes that show continuous variation
·
Discontinuous variation
>
-
All
organisms in the population fall on a
-
*
For phenotypes showing discontinuous variation ,
continuum between two phenotypic extremes be placed into on e of small
organisms can a
,
>
-
Controlled by the alleles of
many genes (polygenic number of phenotypic groups
Phenotypes showing
* >
these phenotypes 1
-
continuous variation
-
controlled
are are
usually by gene
impacted by the environment (monogenic
>
100 %
-
e g
. genetically controlled no environmental
-
.
frequency -
-
.
7 impact 2
.
g
MM11
.
height
frequency
.
7
blood
group
The benefit
to a population of genetic variation :
mem
If a
population is made up of genetically identical Selective pressure :
the abiotic or biotic environmental
organisms & the environment is stable ,
then the factor that determines the value
whole population can survive .
of an allele (which will lead to
greater
↳ Also this well-adapted
, genome will be passed reproductive success .
=>
on to all offspring. However , no environment is If selective
pressures change the alleles , providing
stable forever When it .
changes ,
none of the organisms a selective advantage or
disadvantage will also change
will be able to tolerate the new conditions >
-
Population
goes extinct 1) Natural selection : alleles that result in an advantageous
phenotype will result in
greater reproductive success
How does variation in a
population change ? These alleles will be passed frequently to
on more
offspring
-
-
Gene Pool all alleles of all genes population & their frequency
in in the population will
:
a . increase
<
pop .
W/ high genetic diversity has a
large gene pool falleles resulting in a
poorly adapted phenotype will become less
Allele frequency : The proportion of organisms in a
frequent)
population that carry particular allele The change allele leads to change in the
-
a in
frequency a
average
phenotype This .
is evolution .
