9/27/2022
Chapter 4
From Variant to Species
CHAPTER PREVIEW
Change in evolutionary theory
throughout the 20 th century
Variation, selection, and adaptation
What is a species / speciation?
Methods of species classification
4‐2
KEY TERMS
founder effect clades
variability gene flow
Hardy‐Weinberg genetic drift
Equilibrium genetic
speciation bottleneck
hybrid zones homologous
morphospecies traits
chronospecies homoplasies
anagenesis convergence
cladogenesis parallelism
4‐3
Copyright © 2015 by Nelson Education Ltd. 1
, 9/27/2022
variant to variation
Variant
Individuals within
a population
Variability
Different versions of
a trait
Variation
Range of expression of
a trait
Continuum of expression
(genotypes or phenotypes)
Variation is what’s needed for
natural selection and evolution
to occur
LO1 4‐4
What Darwin didn’t know
Where variation came from (Mutation)
How it was maintained and passed on from
parents to offspring (Mendelian inheritance)
Evolution: The Modern Synthesis (Julien Huxley,
1942). Basically Evolution by Natural Selection
with some understanding of genetics.
Evolution is the production (by mutation) and
redistribution (by NS) of genetic variation in a
population from one generation to the next
What Huxley didn’t know either
Natural selection is not the only force changing
gene frequencies from one generation to the
next:
Microevolutionary forces:
Mutation
Natural Selection
Gene Flow
Genetic Drift
Copyright © 2015 by Nelson Education Ltd. 2
, 9/27/2022
Micro and macroevolution
Microevolution ‐ small
genetic changes that
occur within a population
to make it better suited
to its environment
Macroevolution ‐ big
changes after many
generations (e.g. the loss
or formation of a new
species)
Mutation
Caused by exposure to chemicals, radiation, sunlight,
nothing . . .
Point mutations
Chromosomal mutations
Random with respect to the needs of the organism
Mutations can be deleterious (bad), neutral or good
Mutation is the source of all brand new
genetic material or biological variation
Natural Selection
The differential survival
and reproductive
success of individuals
in each parental
population (generation)
And over time this leads
to… adaptation
http://www.newyorkapologetics.com
Copyright © 2015 by Nelson Education Ltd. 3
Chapter 4
From Variant to Species
CHAPTER PREVIEW
Change in evolutionary theory
throughout the 20 th century
Variation, selection, and adaptation
What is a species / speciation?
Methods of species classification
4‐2
KEY TERMS
founder effect clades
variability gene flow
Hardy‐Weinberg genetic drift
Equilibrium genetic
speciation bottleneck
hybrid zones homologous
morphospecies traits
chronospecies homoplasies
anagenesis convergence
cladogenesis parallelism
4‐3
Copyright © 2015 by Nelson Education Ltd. 1
, 9/27/2022
variant to variation
Variant
Individuals within
a population
Variability
Different versions of
a trait
Variation
Range of expression of
a trait
Continuum of expression
(genotypes or phenotypes)
Variation is what’s needed for
natural selection and evolution
to occur
LO1 4‐4
What Darwin didn’t know
Where variation came from (Mutation)
How it was maintained and passed on from
parents to offspring (Mendelian inheritance)
Evolution: The Modern Synthesis (Julien Huxley,
1942). Basically Evolution by Natural Selection
with some understanding of genetics.
Evolution is the production (by mutation) and
redistribution (by NS) of genetic variation in a
population from one generation to the next
What Huxley didn’t know either
Natural selection is not the only force changing
gene frequencies from one generation to the
next:
Microevolutionary forces:
Mutation
Natural Selection
Gene Flow
Genetic Drift
Copyright © 2015 by Nelson Education Ltd. 2
, 9/27/2022
Micro and macroevolution
Microevolution ‐ small
genetic changes that
occur within a population
to make it better suited
to its environment
Macroevolution ‐ big
changes after many
generations (e.g. the loss
or formation of a new
species)
Mutation
Caused by exposure to chemicals, radiation, sunlight,
nothing . . .
Point mutations
Chromosomal mutations
Random with respect to the needs of the organism
Mutations can be deleterious (bad), neutral or good
Mutation is the source of all brand new
genetic material or biological variation
Natural Selection
The differential survival
and reproductive
success of individuals
in each parental
population (generation)
And over time this leads
to… adaptation
http://www.newyorkapologetics.com
Copyright © 2015 by Nelson Education Ltd. 3
