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Transcript
Evolutionary Trees in the
Ecological Garden
Chapter 2
How did we get so may different
organisms?
Non Evolutionary systems
•
•
Biblical, creationist system
Lyle view on change (pre Darwin)
Evolutionary systems
3. Lamarckian system
4. Evolution by natural selection (Darwin)
Biblical, creationist view
• Life arose
by special
creation
• Species
do not
change
Organisms formed as we find them today
Lamarckian system
No extinctions, many origins
•Change is linier from simple to complex
•Very much a creationist view
Lye View
• Extinctions
take place
• Creations take
place
• Organisms do
not change
Darwin’s Evolution
• Life on earth is ancient
• Species change over long
periods of time time a
descent with modification by
means of natural selection
• Species are related to each
other as ancestordescendant
Link to virtual tour
Darwin's house and
writings
Darwin Vs Lamarck
Theories
of
Change
Over
Time
1.
2.
An evolutionary relationship exists among
groups of organisms
Reflects single unique history of life
3.
Change over time from
many, non related
starting points
Speciation
• Speciation: when new
species evolve from
existing species
• Speciation is
represented as a “fork
in a branch
• Extinction “prunes”
branches from the
evolutionary tree
Evolutionary Anastomosis: Branch
Evolution of longlasting species
fusion:
Rare and IMPORTANT
Phylogeny & Parsimony
• Many patterns are
possible for each
evolutionary tree
• Less complicated
explanations more
likely to be correct
– In evolutionary
biology, phylogenies
that require fewer
evolutionary
transitions more
likely to be correct
Four transition states or one?
Parsimony:
Let’s make a tree
Who is the close relation?
Less complicated explanations more
likely to be correct
• Identify traits shared
by some, but not all of
the organisms
–
–
–
–
Fur
Live offspring
Teeth
Flight
Which would you pick?
Us the tree with the fewest
transition events, It may not be correct,
but it is more probable that a more
complicated proposal.
Characteristic transitions
Selection for
flight –
Twice !!
Selection for fur
Selection for teeth
•Selection for live
births rather than
eggs
Make a Tree, make it simple
Homology and Analogy
• Homology (modern sense): similar by
descent or ancestry
• Analogy: similar not by descent
– In conversation: ‘let me compare thee to a
summers day’
– In biology: similar selection pressures produce
similar adaptations
• E.g. desert plants in N. America share many water
saving features with other desert plants
Important Trees
1. Three Domains of life: Above
kingdoms!!
2. Each domain has been separated
into seven kingdoms
Bacteria
Archaea
Universal
ancestor
Eukarya
Kingdoms - now there are Eight?
Looking for LUCA
(the Last Universal
Common Ancestor
How many kingdsoms?
Six kingdom
taxonomists
Seven kingdom
taxonomists
More that seven
kingdom taxonomists
Three domains rule!
link
Origin of Eukaryotes: Endosymbiosis Theory
Anastomosis
link
Eukaryotic nuclei
do not share recent
ancestors with the
genes of their
organelles, but
rather that of
bacterial genomes
Vertebrate forelimbs
Trees and evolution
• When we cluster
organisms based on
similarities, we find other
similarities: There are no
insects with calcified
bones, or bats with
feathers
Biological classification is a reflection of
evolutionary history
Fossil evidence & patterns of change
Fossils provide information that makes it possible to
reconstruct evolutionary sequences over time
What about fossils?
Fossils provide three types of evidence
for evolution
• Evidence of extinction
• Evidence of change of species through time
• Evidence of age of life
Change through time:
Transitional fossils
• Fossils species intermediate between
modern living forms
• Fossil species intermediate between older
and younger fossils, or older fossils and
modern forms
Biogeographic patterns
• Evolution is
local, and
species migrate
from their
point of origin
• There are
“hotspots” for
change in the
warm tropical
regions
• link
Human embryo with
tail
Developmental patterns &
evolution
Comparative
model
• If you built a flying limb from scratch, you
would design it differently than you would
design a swimming or grasping or running
limb
• The similarity of structure despite very
different function suggests similarity of
origin
• Adaptations are the response to natural
selection
Homology
• A similarity between species that is not
functionally necessary.
– Structural homology
– Developmental homology
– Genetic homology
Genetic Homology
• Structural homologies are similar because
they share developmental homology
• Developmental homology is the result of
genetic homology
‘Universal’ genetic codeOther
homology examples
Genetic homology in
homeodomain eye genes
Thought question
• Biomedical researchers often seek
treatments for human disease by doing
experiment in other species (e.g. mice)
• How successful would they be if mice and
humans did not share numerous
homologies?
Examples of vestigial traits
Also:
Your appendix
Wisdom teeth
Goose bumps
Vestigial traits can be:
• Structural
– Tail bone in adult humans
• Developmental
– Embryonic tail
Vestigial Genes
• Genetic
– Pseudogenes: nearly normal genes that are not
transcribed to protein
– E.g., psi-alpha locus of hemoglobin
– Resembles that alpha locus but has a mutation
that stops transcription
Homoplasy: convergent evolution
• Shared
characteristi
cs of non
related lines