Transcript Evolutionary Trees in the Ecological Garden

Evolutionary Trees in the
Ecological Garden
Pre-Darwin thoughts
Life arose by special creation
• Organisms were formed as
we find them today
– That is species do not change
• Creation as a recent event
– In 1664 Archbishop
James Ushher calculated
that the earth was 5668
years old
– 26th of October, 4004
B.C., 9 AM
A comparison
• Species created
independently
• Species do not
change through time
• Created recently
• Process is creation
(God did it)
• Species are related to
one another
• Species change over
time
• Life on earth is
ancient
• Process: descent with
modification’, by way
of natural selection
Darin was not the first to question
the Biblical scheme
• Charles Lyell (geologist) accepted the concept of
extinctions, and that not all species were created
at the same time
• He proposed a “natural” process of extinction –
but creation remained a mystery
• Darwin proposed natural (“materialistic”)
processes for both creation of new species, and
extinction
The Larckian System
• A linear progressive evolution – a species
changed over time.
• There were many starting points.
• Species did not go “extinct” they became
more complex life forms
• Based on transmittance of characteristics
by use and disuse
The Tree
concept
• The evolutionary relationships among
groups of organisms
– Reflects single unique history of life
• When new
species
evolve from
existing
species –
the event is
called
speciation
Speciation
How to make a tree
• Principle of
parsimony
– Less complicated
explanations more
likely to be correct
– In evolutionary
biology,
phylogenies that
require fewer
evolutionary
transitions more
likely to be correct
Which would
you pick?
Parsimony
determines
the best
answer
Applying cladistic methods
A clade is a grouping that includes a common ancestor and all the
descendents (living and extinct) of that ancestor.
• Identify synapomorphic
traits based on
• Structural,
• Developmental
similarities
• Genetic comparisions
• Use parsimony to infer
phylogenetic relationships
• Validating and assessing
tree
Building Evolutionary Trees
• Chose the taxa
• Determine the
characteristics
• Identify a probable order
of evolution for each
character
• Group organisms by
changed characteristics
(synamorphy)
• Check for parsimony
• Remember – each tree
is a theory & may be
changed to meet
challenges of new
discoveries
• reference
Biological classification is a
reflection of evolutionary history
• Why is this so?
• Descendants of common ancestors
differentiate from one another
• Fossils provide a glimpse of the process
– and information about the timeline
What are the evolutionary
transitions?
Modern evolutionary
trees
• Species can
split or merge,
some species
die out
Synamorphy
• A derived or
changed character.
That can be used as
indicators of
common ancestry.
– Consider a ancestor
of a beetle clade had
five antennal
segments and
passed that
character state onto
its immediate
descendents
– one lineage within
the clade evolved six
antennal segments
Bird evolution: and Example
of use of Synamorphy
Example: the evolutionary
relationships of whales
Three dominions
• Bacteria
• Eucarya
• Archaea
• Reference 1
• Reference 2
Archaea
Like th Eukarya they
have Histones and
Introns
Histones: Act as spools around which DNA winds
and they play a role in gene regulation.
Introns are sections of DNA that will be spliced
out after transcription, but before the RNA is
used.
Evolution of Eukaryotic life
Lack the histones and
introns, of Archaea and
Prokaryots.
Parasexual transfer of
genetic information
Conjugation, transduction
and transformation
Evolution of
Bacteria
Exploring the tree of life
• Remember – every
phylogeny is a
hypothesis and is
subject to debate and
revision.
• Link to tree of Life
• Modern View is of a
Tree – Not a Ladder
– Eukaryotes Tree
The “ladder of life”
as per Aristotle
Developmental patterns
• Why are embryos less differentiated than
adults?
• Is this true for insects?
• Parallel patterns in evolution: Support for
evolution directed by natural selection
A phylogeny is a hypothesis
What data might test these
hypotheses?
• Morphology, including
fossils
• DNA sequences