Download Chapters 25-26 V2

Chapters 25 and 26
The Origin of Life as we know it.
► Phylogeny
– traces evolutionary history of
taxa
► SystematicsSystematics- analyzes relationships (modern
and past) of organisms
Figure 25.1 A gallery of fossils
Searching for Homology
► Morphological
and molecular similarities
among living organisms
Organisms similar in appearance also are often
similar in molecular makemake-up (DNA and thus
protein sequences)
WHEN IS THIS NOT TRUE?
The fossil record can be
used to trace evolutionary
relationships between
organisms of the past and
those of the present
Figure 25.5 Convergent evolution of analogous
burrowing characteristics
Figure 25.6 Aligning segments of DNA
1 Ancestral homologous
DNA segments are
identical as species 1
and species 2 begin to
diverge from their
common ancestor.
1 C C A T C A G A G T C C
2 C C A T C A G A G T C C
Deletion
2 Deletion and insertion
mutations shift what
had been matching
sequences in the two
species.
1 C C A T C A G A G T C C
2 C C A T C A G A G T C C
G T A
Insertion
Marsupial Australian mole
3 Homologous regions
(yellow) do not all align
because of these mutations.
4 Homologous regions
realign after a computer
program adds gaps in
sequence 1.
1
C C A T
C A
2
C C A T
G T A
A G T C C
C A G
A G T C C
1
C C A T
C A
A G T C C
2
C C A T
G T A
C A G
A G T C C
Eutherian North American Mole
1
Phylogenetic Systematics
► Taxonomy
is the science of naming and
classifying life
Relies on Binomial nomenclature in which each
organism (Species) is given a unique name that
includes:
►Kings
Play Chess On Fine
Glass Stools
►Genus
►Specific
epithet
Homo sapiens vs. Homo erectus
Figure 25.7 Hierarchical classification
Figure 25.8 The connection between classification and phylogeny
► Phylogenetic
trees show
evolutionary
relationships
that also reflect
hierarchical
classification
► Clade
► Monophyletic
► Derived
Characters
► Primitive
Characters
► Monophyly
– ancestor and all of its
descendents
► Paraphyly – group includes ancestor and
some of its descendents
► PolyphylyPolyphyly- multiple groups lack a common
ancestor
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Figure 25.11 Constructing a cladogram
► Ingroup
► Outgroup
► Parsimony
Ultrametric
Trees
Phylograms
► reflect
the numbers of
changes that have
taken place in a
particular gene
sequence.
► Place
data in context
of geologic time
Branch length is
correlated with
differences
► Homology
vs. Analogy
in constructing trees
► Cladistics
is changing the way we classify
organisms
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Table 25.1 The Geologic Time Scale
The history of life
Chapter 26
Figure 26.0 A painting of early Earth showing volcanic activity and photosynthetic prokaryotes
in dense mats
► Miller
and Urey
Experiments
demonstrate
how
atmospheric
conditions could
have favored
the start of life.
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Figure 26.12 Laboratory versions of protobionts
Figure 26.14 A window to early life?
Figure 26.11 Abiotic replication of RNA
► RNA
was the first genetic material
► Ribozymes
► Ribozymes
are used to synthesize tRNA,
tRNA, mRNA,
rRNA
(a) RNA forms
(d) RNA encodes both DNA and proteins
Nucleotides
RNA
(b) Ribozymes catalyze RNA replication
DNA
RNA
(c) RNA catalyzes protein synthesis
Amino acids
Protein
Protein
(e) Proteins catalyze cell activities
Plasma
DNA
membrane
Protein
Q: Why do you think RNA arose
before DNA?
Bacterial
cell
Hint: what limitations does DNA have
structurally?
► RNA
is autocatalytic, DNA is not
molecules can take on many conformations,
DNA is limited to double stranded helix
► RNA can be used to synthesize proteins
► RNA
►Why
is DNA the primary genetic
material today??
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Sedimentary deposit
Figure 25.2 Radiometric dating
► Relative
datingdatingcomparing layers in
sedimentary layer
at different sites to
get time frames
► Radiometric
dating – allows us to get absolute
dates based upon relative abundances of
radioactive isotopes.
Figure 25.5 Diversity of life and periods of mass extinction
Five major
extinctions
440 MYA, late Ordovician - global cooling
365 MYA, late Devonian - global cooling and anoxia of
seas,
► 245 MYA, End of Permian - 8080-96% of marine species
went extinct, sustained cooling
► 210 MYA, End of Triassic - possibly related to increased
rainfall ► 65 MYA - KT (Cretaceous(Cretaceous-Tertiary) - 6565-70% of marine
species went extinct, end of the dinosaurs, likely due to
large impact event
►
►
Figure 25.6 Trauma for planet Earth and its Cretaceous life
►
Volcanic activity and
lightning associated
with the birth of the
island of Surtsey near
Iceland; terrestrial life
began colonizing
Surtsey soon after its
birth
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3.5 billion years ago
► First
evidence of life
appears
► Oldest fossils are
from Australia
Stromatolites
► Prokaryotes
dominated
evolutionary history
until 2.0 billion
years ago
Figure 26.3 Early (left) and modern (right) prokaryotes
Figure 26.4 Bacterial mats and stromatolites
Bacterial mats in
Baja California
Top: Mat from Baja
Bottom: Stromatolite from
Australia – 3.5 billion years old
Figure 26.4x Stromatolites in Northern Canada
Figure 26.14 A window to early life?
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2.7 billion years ago
Figure 26.5 Banded iron formations are evidence of the vintage of oxygenic
photosynthesis
► oxygen
starts to
accumulate
► Photosynthesis that
involves the splitting of
water evolves:
produces lots of O2
CO2 and 6 H20 + energy C6H12O6
+ 6 O2
Q. What would be the selective
advantage to adapting to the new O2
environment???
► A.
2.1 Billion years ago
► Eukaryotes
Anaerobic vs. aerobic metabolism!!!
Just think of all that ATP!!!!!
(a) Progenitor of eukaryotes
arise
Endosymbiosis
Membrane infolding
(c) Ancient eukaryote
Mitochondrion
Plasma
membrane
Nulear
envelope
DNA
Endoplasmic
membrane
(d) Eukaryotic protist, fungus,
and animal cells
(b) Proto-eukaryote
(e) Eukaryotic plant cell
Cell wall
Chloroplast
Invagination of
cell membrane
Future
nuclear
envelope
Protosynthetic
prokaryote
Mitochondrion
Bacterium
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1.2 Billion years ago
Lines of evidence
► Multicellularity
• Size of modern and fossil bacteria
• Divide by a process similar to binary fission
• Inner membranes are similar to those found in
modern day prokaryotes
• Have their own genomes, ribosomes, tRNAs
and proteins
arises
Fossilized alga
about 1.2 billion
years old
– SSU-rRNA comparisons
Fossilized animal embryos
from Chinese sediments
570 million years old
Multicellular life may have evolved from
colonial protists
► Multicellularity
evolved independently many
times
Probably by specialization of the cells of colonial
protists
Gamete
1
2
Locomotor
cells
Somatic
cells
3
Foodsynthesizing
cells
Unicellular
protist
Colony
Early multicellular organism with
specialized, interdependent cells
Later organism that
produces gametes
Cambrian period (543 -510 mya)
mya)
► Animal
diversity
EXPLODES!!!
► Almost all major phyla
of animals appear
including Cnidarians
and Poriferans (jellies
and sponges)
9
500 mya
arrive on land
(FINALLY)
► Plants, fungi and
animals all colonize the
land
► Major event in shaping
terrestrial life as we
know it today.
Modern humans
(Homo sapiens)
appear about
2 seconds
before midnight
► Plants
Age of
reptiles
Insects and
amphibians
invade the land
Age of
mammals
Recorded human
history begins
1/4 second
before midnight
midnight
Origin of life
(3.6–3.8 billion
years ago)
Plants
invade the
land
First fossil
record of
animals
Plants
begin
invading
land
noon
Evolution and
expansion of life
The tree of life
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