Transcript 2/11 - University of Texas

Exams returned W 2/13----Bonus #1 due F 2/15
As DNA changes;
traits change.
DNA
Traits
Evolution: changes in DNA as information transmitted
O
O
O
O
O
O
O
O
Bacteria with mutation
causing resistance
O
O
O
Changes to groups,
not individuals.
Evolution: changes in DNA as information transmitted
O
O
O
O
O
O
O
O
Bacteria with mutation
causing resistance
O
O
O
Apply
antibiotic
Changes to groups,
not individuals.
O
X
O
O
X
O
O
O
O
Kills most bacteria.
Except if some have mutation
that allow them to be resistant.
X
O
O
X
X
O
X
X
X
O
O
X
X
O
Continues to
replicate
O
O
O
O
O
O
O
O
O
O
Population of resistant bacteria
Evolution: A
species’ genetic
component
changes as the
individuals
reproduce.
These changes
are based on
how the DNA
changes and
who
reproduces.
Natural Selection:
Individuals that are most
successful at reproducing will
pass on more of their genetic
information.
Reproductive success = evolutionary success
Are genes the only replicators?
Memes: transmissible ideas
• Ideas can act similarly to genes
– Contain information
– Replicate with imperfect fidelity
Mutations
Memes: transmissible ideas
• Ideas can act similarly to genes or viruses
– Contain information
– Replicate with imperfect fidelity
Memes: transmissible ideas
• Ideas can act similarly to genes or viruses
– Contain information
– Replicate with imperfect fidelity
Evolve: most successful replicators become
most abundant
Contrasts between memes and genes
Genes
Memes
• Slow replication
• Rapid replication
• High copy fidelity
• Low copy fidelity
• Universal in organisms • Limited to some
organisms
– Only humans can
transmit complex
memes?
Evolution of memes and genes
Selection of memes and genes
can be at odds
NvN chpt 8
Humans can pass on genes
and/or memes
Do memes make humans
unique?
Human Population Growth
Natural Selection:
Individuals that are most
successful at reproducing will
pass on more of their genetic
information.
Artificial Selection:
Individuals chosen by humans
will reproduce and pass on their
genetic information.
from Teosinte
Maize
By artificial selection that
began ~10,000 years ago.
Artificial selection
1. Select individuals
that have the largest
side buds and breed
them.
Number of Individuals
Wild Brassica oleracea:
small side buds
2. Of the offspring,
select individuals that
have the largest side
buds and breed them.
3. Of the offspring,
select individuals that
have the largest side
buds and breed them.
4. After several
generations, bud size
increases dramatically.
0
Brussels sprouts:
extremely large side buds
1
2
Size of buds (cm)
3
Wild Brassica oleracea:
small side buds
Selection only works if there
is variability in the
population
Artificial selection
Number of Individuals
1. Select individuals
that have the largest
side buds and breed
them.
2. Of the offspring,
select individuals that
have the largest side
buds and breed them.
3. Of the offspring,
select individuals that
have the largest side
buds and breed them.
4. After several
generations, bud size
increases dramatically.
0
Brussels sprouts:
extremely large side buds
1
2
Size of buds (cm)
3
Different foods
from one
species of plant.
Created by
artificial
selection.
CB 22.10
Individuals are selected…
But populations evolve via changes in
DNA during reproduction.
Evolution can only occur when
both of these conditions are met:
•Genetic diversity gives rise to
individuals with different traits
and
•Not all individuals can reproduce
CB 22.9
CB 23.11
Variation of a trait within a species
Three basic types of selection…
• Directional
• Stabilizing
• Disruptive
CB 23.12
Directional Selection
Directional Selection
has led to an increase
in swallow size
CB 23.12
Stabilizing Selection
Human birth weight has been stably selected
CB 23.12
Disruptive Selection
Disruptive Selection in blackbellied
seedcrackers
CB 23.12
The three different types of selection
Evolution:
A species’ genetic component changes as the
individuals reproduce due to…
•Non-random changes (natural selection)
•Random changes (genetic drift/bottleneck)
•Mutations add new alleles or genes
Exams returned W 2/13----Bonus #1 due F 2/15