Transcript Developmental Biology and Evolution

Developmental Biology and
Evolution
佟超
浙江大学生命科学研究院
Outline
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Overview
Preconditions for evolution
Deep homology
Mechanisms of evolutionary changes
Developmental constrains on evolution
Selectable epigenetic variation
Summary
What is Evolution ?
What is Evolution ?
Evolution is the change in the inherited characteristics
of biological populations over successive generations.
Evolutionary processes give rise to diversity at every
level of biological organization, including species,
individual organisms and molecules such as DNA and
proteins.
What is Evolution ?
• Descent from a common ancestor
• Natural selection
• At the different level
Timeline of evolution theory
1735
biological
classification
1809
Lamarckism
1858
0n the origin of species
1865
Mendel's laws
population genetics
1896
Weismannism
“germ cells vs
Somatic cells”
1953
DNA structure
Galapagos
Summary of Darwin’s theory
Every species is fertile enough that if all offspring survived to reproduce the
population would grow (fact).
Despite periodic fluctuations, populations remain roughly the same size (fact).
Resources such as food are limited and are relatively stable over time (fact).
A struggle for survival ensues (inference).
Individuals in a population vary significantly from one another (fact).
Much of this variation is inheritable (fact).
Individuals less suited to the environment are less likely to survive and less
likely to reproduce; individuals more suited to the environment are more likely
to survive and more likely to reproduce and leave their inheritable traits to
future generations, which produces the process of natural
selection (inference).
This slowly effected process results in populations changing to adapt to their
environments, and ultimately, these variations accumulate over time to form
new species (inference).
Ernst Mayr
Why we need to understand evolution?
"nothing in biology
makes sense except in
the light of evolution"
Theodosius Dobzhansky
Basics of Biology
• Theory of evolution
• Mendelian inheritance
• The central dogma of molecular biology
How “far” away they are
How “close” they are
How does evolution work
• Preconditions for evolution: The
developmental structure of genome
• Modularity
• Molecular parsimony The small tool kit
Modularity: Divergence through
dissociation
Modularity: Divergence through
dissociation
• Apterous
Molecular parsimony: gene
duplication and divergence
• Some “tool kit” genes play the same roles in
all animals
• Gene duplication provides opportunities for
divergence.
• Paralogues
• Orthologues
Molecular parsimony: gene
duplication and divergence
Deep Homology
Mechanisms of evolutionary change
Evolution works with what it has:
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Change in location (Heterotopy)
Change in time (Heterchrony)
Change in amount (Heterometry)
Change in kind (Heterotypy)
Heterotopy
Fgf8
BMP
apoptosis
Heterotopy
Fgf10 attract ribs to enter the dermis
BMP induce the bone formation
Heterchrony
Heterometry
• Darwin’s finches
Heterometry
Heterotypy
• Why insects have only six legs?
Developmental constraints on
Evolution
• Physical constraints
• Morphogenetic constraints
• Phyletic constraints
Physical constraints
Morphogenetic constraints
Phyletic constraints
Selectable epigenetic variation:
Environment cues
• Somatic cells VS germ cells
What is wrong with lamarck?
• Epialleles
• Symbiont variation
• Genetic assimilation
Epialleles
Symbiont variation
Interaction with an expected population of
symbionts could result in phenotypic plasticity.
When symbionts are transmitted through the
germ line, the symbionts provide a second
system of inheritance.
Symbiont variation
Genetic assimilation
• The environment could both “induce” and
“select” a phenotype.
• Genetic assimilation happens both in labs and
in nature.
• Fixation of environment induced phenotypes
1. The phenotype is not random.
2. The phenotype already exists in a large
portion of population
Summary
• Variation-modularity, molecular parsimony, and
duplication- enable changes in development
without destroy the organism.
• Four modes of genetic changes act during
development to produce new and large variation
in morphology.
• Epigenetic inheritance provide selectable
variations and aid their propagation through a
population.