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There is a Great Diversity of Organisms

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Title: There is a Great Diversity of Organisms


1
There is a Great Diversity of Organisms on
Planet Earth.why?
2
What Best Explains Diversity?
I. Special Creation
II. Evolution
Aristotle to Darwin 350 BC to 1800s
Darwin to Present
(A) Each organism originated independently. (B)
Since the time of creation, each organism has
remained the same. (C) All organisms were
created recently.
(A) All organisms originated from common
ancestors. (B) Organisms have and continue to
change over time. (C) Evolution of organisms
began 3.7 billion years ago
3
For a more details concerning the History of
Evolutionary Thought
http//www.ucmp.berkeley.edu/history/evolution.htm
l
For information about the Evolution/Creationist
Controversy
http//www.talkorigins.org/
National Center for Science Education
http//www.natcenscied.org/
4
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
5
Lamarck
  • Believed in inheritance of acquired
    characteristics (acquired during life)

Change Inherited by Offspring
Change Inherited by Offspring
Parents
Parents Change During Lifetime
Parents Change During Lifetime
Parents Change During Lifetime
6
Inheritance of Acquired Characteristics
7
Importance of Lamarcks 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

8
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

9
The only figure in On the Origins.
10
Darwins Idea of Common Decent Implies (1)
Branching evolution (2) That species accumulate
differences over time
Genus 1
Genus 2
Species 1
Species 2
Species 5
Species 2
Species 3
Species 1
Species 4
Extinction
Differences Accumulate Over Time
11
Systematists Study Differences Among Species to
Reconstruct Phylogeny
(i.e. Phylogeny Genealogy of Species)
http//phylogeny.arizona.edu/tree/
12
Evolution by Natural Selection
13
What is adaptation?
  • Process of genetic change whereby individuals of
    a population become better suited to their
    environment

14
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15
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16
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.
17
The Modern Synthesis (1930s - 40s)
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.

18
MS concepts from Laboratory Genetics
P G E Phenotype Genotype Environment
1.
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.
19
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.
20
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.
21
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
Non- Darwinian mechanisms (orthogenesis,
major-mutational origins, Lamarckian evolution).
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