Download Aug27_1_04 - Salamander Genome Project

There is a Great Diversity of Organisms
on Planet Earth……….why?
What Best Explains Diversity?
I. Special Creation
Aristotle to Darwin
~350 BC to 1800s
II. Evolution
Darwin to Present
(A) Each organism
originated independently.
(A) All organisms originated
from common ancestors.
(B) Since the time of
creation, each organism
has remained the same.
(B) Organisms have and
continue to change over
time.
(C) All organisms were
created recently.
(C) Evolution of organisms
began 3.7 billion years ago
For a more details concerning the History of Evolutionary Thought:
http://www.ucmp.berkeley.edu/history/evolution.html
For information about the Evolution/Creationist Controversy:
http://www.talkorigins.org/
National Center for Science Education:
http://www.natcenscied.org/
Jean-Baptiste de Lamarck (1744-1829)
First Theory of Evolution
Transformational Evolution
Humans
Mammals
Amphibians
Scale
Of
Nature
Fish
Insects
Jellyfish
Zooplankton
Pond Scum
Time
Lamarck :
• Believed in inheritance of acquired
characteristics (acquired during life)
Parents
Parents
Change
During
Lifetime
Change
Inherited by
Offspring
Parents
Change
During
Lifetime
Change
Inherited by
Offspring
Parents
Change
During
Lifetime
Grows up
Among Short
Trees
Inheritance of Acquired
Characteristics
Two Sibling
Giraffe’s
Grows up
Among Tall
Trees:
Longer neck
Importance of Lamarck’s Theory
• Recognized that life forms were
connected
• Recognized that there is variation in
traits
• Recognized that evolution requires
time (Earth is Old).
• Recognized that inheritance is an
important aspect of adaptation
Darwin (1809-1882)
“On the Origins by Means of Natural Selection, or the
Preservation of Favoured Races in the Struggle of Life”
• Two Major Ideas:
– Common Descent
All living and extinct species descended from
one or a few common ancestors.
• aka: Macroevolution
– Adaptation occurs by Natural Selection
The characteristics of organisms change
through time as a result of natural selection.
• aka: Microevolution
The only figure in “On the Origins….”
Darwin’s Idea of Common Decent Implies:
(1) Branching evolution
(2) That species accumulate differences over time
Genus 1
Species 1
Species 2
Genus 2
Species 1
Extinction
Differences
Accumulate
Over Time
Species 2
Species 3
Species
5
Species 4
Systematists Study Differences Among
Species to Reconstruct Phylogeny
(i.e. Phylogeny = Genealogy of Species)
http://phylogeny.arizona.edu/tree/
Evolution by Natural Selection
What is adaptation?
Process of genetic change
whereby individuals of a
population become better
suited to their environment
Evolution After Darwin
Most accepted idea of common descent, but not natural selection.
Competing theories were proposed:
Orthogenesis: variation in the characteristics of organisms
is channeled in pre-determined directions.
Macromutation: downplayed the importance of continuous
variation and stressed discrete variation. Thought evolution
only depended upon mutation rate.
The Modern Synthesis (1930’s - 40’s)
Synthesis of ideas/concepts among geneticists, natural
historians, and evolutionary biologists that modern
evolutionary biology is built upon.
Emphasized the co-action of random mutation, selection,
genetic drift, and gene flow in microevolution.
Emphasized that these evolutionary processes were sufficient
to account for macroevolutionary trends.
MS concepts from Laboratory Genetics
1.
P=G+E
Phenotype = Genotype + Environment
2. Environmental effects on phenotype are not inherited
3. Heredity is based on particles (genes). They retain identity
and do not blend. They give rise to continuous and
discrete variation.
4. Genes mutate at relatively low rates. Recombination is an
important aspect of evolution.
5. Environmental factors can influence mutation rates but do
not yield specific mutations that are seemingly the best for
surviving in a particular environment.
MS concepts from Population Genetics
1. Selection can alter populations beyond the original range of
variation by restructuring genomes through recombination,
and thus give rise to new phenotypes.
2. Natural populations are genetically variable.
3. Populations of a species in different geographic areas may
differ in genetically based characteristics. Genotypic
frequencies may vary among populations. Often differences
are adaptive, and thus a product of natural selection.
4. Experimental crosses among populations or species show
that most characteristics have a genetic basis, and most have
a complex or polygenic basis. This suggests that evolution may
occur through small steps.
MS concepts from Population Genetics (cont.)
5. Organisms are not necessarily different species if they exhibit
different characteristics. A species is a collection of populations
that interbreed, and is thus characterized by a common gene pool.
(i.e. Biological Species Concept)
6. However, there is a continuum of differences among populations
and even in the degree of reproductive isolation. There are also a
continuum of differences observed among species, or genera, or
higher taxonomic classifications. This provides evidence that an
ancestral species differentiates into two or more different species.
7. Speciation generally occurs through the genetic differentiation
of geographically separated populations. This creates isolation
and prevents gene flow.
MS concepts from Systematics/Paleontology
1. The fossil record has gaps among quite different organisms.
This reflects the incompleteness of the fossil record. However,
there are gradations or intermediates that fill some gaps. It seems
likely that the evolution of large differences occurs through many
small steps that are fixed over very long time periods.
2. All observations in the fossil record are consistent with
evolutionary principles and there is no need to invoke NonDarwinian mechanisms (orthogenesis, major-mutational origins,
Lamarckian evolution).