Download Unifying Concept in Biology - Carol Lee Lab

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(6) Why am I taking this class?
EVOLUTION
The Unifying Concept in Biology
Dr. Carol Eunmi Lee
University of Wisconsin, Madison
“Nothing in biology
makes sense except in
the light of evolution”
Theodosius Dobzhansky (1900-1975)
Reading
(1) Evolutionary Analysis
5th Edition, 2013
Jon Herron & Scott Freeman
(2) Journal articles posted
on Course Website
Course Website

https://mywebspace.wisc.edu/carollee/web/Lee/Ev
olution410.html
Background needed for this
course

Some understanding of basic genetics
(Hardy Weinberg Equilibrium, DNA,
RNA, transcription, translation, allele,
genotype)
OUTLINE:
1) Overview
2) What is Evolution?
3) Basic Concepts
3) Practical Applications
4) Example of Evolution in Action: Evolution of HIV
Course Overview:
(1) TODAY: What is Evolution? Practical Applications
(2, 3) History of Evolutionary Thought
(4) Hardy Weinberg Equilibrium (no evolution), Genetic Drift
(5) EVOLUTIONARY MECHANISMS: Genetic Drift
(6, 7) EVOLUTIONARY MECHANISMS: Genetic Variation
(8) EVOLUTIONARY MECHANISMS: Epigenetic Inheritance
(9,10) EVOLUTIONARY MECHANISMS: Natural Selection
(11, 12) Molecular Evolution
(13, 14) Genome Evolution
(15, 16) Evolutionary Tradeoffs
(17, 18) Speciation
(19, 20) Earth History, History of Life on Earth
(21, 22) Reconstructing the Tree of Life
(23) Microbial Evolution
(24) Plant Evolution
(25, 26) Animal Diversity
(27, 28) Human Evolution
Structure of Lectures:
Introduction
&Background
What is Evolution? Practical Applications
History of Evolutionary Thought
No Evolution
Hardy Weinberg Equilibrium
Evolutionary
Mechanisms
Genetic Drift
Genetic Variation (Mutation, Recombination)
Epigenetic Variation
Natural Selection
(including molecular and genome levels)
Macroevolution
Speciation
History of Life on Earth
Tree of Life
Diversity
Microbial Evolution
Plant Evolution
Animal Diversity
Human Evolution
Grading & Exams
• 3 exams of equal weight, multiple choice:
100 points each = 300 pts total
• 3 quizzes: 20 points each = 60 pts total
• 3 homeworks: 30 points each = 90 pts total
• In-class extra credit, unannounced random
dates: 50 pts
300 (exams) + 60 (quizzes) + 90 pts (homework)
+ 50 pts (extra credit) = 500 points total
Q: What is Evolution?
Q: How does Evolution Occur?
Q1: What is Evolution?
Q1: What is Evolution?
(give the most comprehensive answer)
(1) The increase in fitness over time due to natural
selection, or adaptation.
(2) The accumulation of mutations, which alter fitness
over time.
(3) The change in allele frequencies (or the heritable
expression of those alleles) in a population across
generations.
(4) The progression into more complex forms of life
Q1: What is Evolution?
(give the most comprehensive answer)
The change in allele frequencies (or the heritable
expression of those alleles) in a population across
generations.
(BB)
Blue
Generation 1:
Generation 2:
Generation 3:
(Bb)
Purple
250
200
100
500
600
800
(bb)
Red
250
200
100
Although, even if allele frequencies in a population remain the
same across generations, a population is evolving if it goes
out of Hardy-Weinberg Equilibrium (more on this later)
Q: What is Evolution?




Change in proportions of genetically different individuals at
each generation
Leading to an average change in characteristics of
populations over time  change in allele frequencies
(genetic composition) or the heritable change in the
expression of those alleles (epigenetic inheritance)
Acts by removing individuals from the population, or by
allowing some to leave more offspring
By population, we are referring to a group of interbreeding
individuals and their offspring (in the case of sexual species)
Q3: How does Evolution Occur?
Q3: How does Evolution Occur?
***Through
5 Major Mechanisms:

Genetic Drift
Mutation

Heritable Epigenetic Modification



Migration
Natural Selection
(Think about what forces would change the allele
frequencies in a population, or the heritable
expression of those alleles)
i.e. what causes changes in the
allelic composition in a population?

Genetic Drift: totally random changes in allele frequency
from generation to generation

Mutation: changes in the genetic code, such as errors in
DNA replication, gene deletions or duplications, etc…

Epigenetic Inheritance: heritable changes that are not
due to changes in DNA sequence itself, but the expression
of the DNA, such as changes in DNA methylation and
histone modifications, etc…


Migration: alleles moving from one population to another
Natural Selection: when some alleles favored over others
due to an increase in fitness (not random); acts on genetic
variation in the population
Sources of Genetic Variation
Mutation generates
genetic variation
Natural Selection
Natural Selection acts on
genetic or epigenetic
variation in a population
Epigenetic modification
changes expression of
genes
Genetic Drift reduces
genetic variation
Without genetic or
epigenetic variation,
Natural Selection cannot
Evolutionary Concepts
Permeate all Aspects of
Biology
Biotechnology
Agriculture
Medicine
Conservation
Agriculture

Most of your food is
a product of intense
artificial selection, or
human induced
evolution
Evolution of a
Pathogen as an
Example:
I will now use an infectious disease to illustrate
basic evolutionary concepts.
The following example illustrates several
evolutionary mechanisms
I will explain these concepts in more detail over
the next few lectures
HIV: Fastest
evolving organism
on Earth
HIV infects
macrophages,
T-cells
AIDS Pandemic
AIDS is among the most deadly epidemics in Human
History (1981-2009: ~30 million deaths)


~34 million people living with AIDS (estimated 2010)

90 million deaths predicted by 2020
#people living with HIV
UNAIDS. 2008 Report on the
Global AIDS Epidemic
(http://www.unaids.org/en/Knowle
dgeCentre/HIVData/GlobalRepor
t/2008/)
A global view of HIV infection
33 million people [30–36 million] living with HIV, 2007
Problem :




HIV has the fastest mutation rate of any virus or
organism observed to date
HIV evolves more rapidly than humans, and more
quickly than the ability of humans to produce new
drugs
Implications: AIDS vaccines are unlikely to work on all
strains of the virus… …and unlikely to work on a given
strain in the long run
Our understanding of how to combat viruses had in general been
poor, and the recent intensive research on HIV has greatly
enhanced our understanding of how to combat viruses in general
Questions:
(1) What is Evolution?
(2) How does evolution operate? What are the main
Evolutionary Mechanisms?
(3) Discuss how an understanding of evolution impacts
practices in Agriculture, Medicine, and Conservation
(4) For example, discuss how different evolutionary
mechanisms impact the evolution of HIV, the virus
that causes AIDS
Concepts
Evolution
Population
Genetic Drift
Natural Selection
Mutation
Genetic Variation
Allele, Genotype
HIV