Transcript Phylogeny and Systematics

Phylogeny
and
Systematics
Figure 25.0 Fossil of a fish: perch
Fossil Formations
Sedimentary Rocks
Petrification
Amber
Figure 25.1 A gallery of fossils
Tracks
Preserved
Table 25.1 The Geologic Time Scale
Dating
•Geological
Time Scale:
Consistent
sequence of
historical
periods
•Relative
Dating:
Consistent
sequence of
sediment
layers.
Absolute Dating:
•Radiometric Dating: measuring certain radio-isotopes w/i
fossils. Carbon accumulated in body over time (C-14), at
death, C-14 decays, (Half life = 5,730 years)
•Uranium-238: Half life of 4.5 billion years, occurs in
lava. Degrades once solidified. (Determines age of rock
layers.
Figure 25.2 Radiometric dating
Phylogeny based on
Continental Drift
Figure 25.3 Earth’s crustal plates and plate tectonics (geologic processes resulting from plate movements)
ontinental drift
Pangaea
•End of Paleozoic Era (250 million)
•Eliminated Isolation
•Increased Competition
•Ocean Basin increased, lowered sea level
•Shallow organisms destroyed
•Mesozoic Era: (180 Mill)
•Pangaea breaks up, continental drift
•Explains current distribution of organisms
•(Eutherian and Marsupials)
Mass Extinctions
•Long period of quiescent, brief species turnover time.
•Habitat destroyed or environmental changes
•Two Major extinction periods:
•Permian=(250 mill); ended 90% of marine animals
many terrestrial life ended, less than 5 mill yrs.
Formation of Pangaea,
•Cretaceous=(65 mill); destroyed 50% marine,
plants and terrestrial animals (dinosaurs)
•B/W Mesozoic and Cenozoic thin layer of iridium
rare on earth, found on meteorites.
Systematics
•Systematics= study of biological diversity in evolution
•Binomial Nomenclature:
•genus
•specific epithet (species)
Hierarchical Classification
Phylogenetic Tree
Clades: Cladogram
Series of dichotomous points: represents divergence of species.
Clade: each evolutionary branch.
•Convergent Evolution: similarity resemble due to similar ecosystems
Similarities called analogy (not homology); wings of bats vs.. birds
•Homologous evolution:likeness due to common ancestry
Shared Characters
•Shared Primitive Characters: homology feature predating a taxon
•
backbones predate the mammalian taxon.
Shared Derived Characters: evolutionary novelty unique to a
particular clade
•Outgroup Comparison: comparison differentiate shared characters
that are derived from those that are primitive.
•Compare against an outgroup organism that is less closely
related than the others.
•Ingroup is the group we are comparing together.
`
Homology present in both In and Out group is notochord.
Ingroup shows shared primitive and shared derived characters.
Turtle-leopard share a common ancestor more recent than
salamander-turtle-leopard clade.
Does not give time relationships
Three possible relationship for the four species.
Parsimony states that the simplest explanation that fits the facts
Is more than likely correct. “Occam’s Razor”
Phylogenetic Trees are
Hypothetical
Parsimony vs.. Analogy vs.. Homology: 4 chamber heart is not
homologous but analogous. 4 chamber heart evolved 2x in
vertebrate evolution. May not be the most parsimonious.
Molecular Clocks
•Some regions of DNA “Evolve” at constant rates.
•Relative dating using reliable genes that evolve.
•Assumes that DNA changes are due to genetic drift, and mostly
are neutral.
•HIV Molecular clock: Host jump, different strains (HIV-1M)
evolves rapidly, Look at evolution of gene in a patient over time.
•Samples collect 1980’s to 90’s, rate of change is constant.
Debates
•Lizards, snakes, crocodiles, and birds
•According to Linnaeus and Darwin, how would he place their
relationship
Lizards-------Crocs--------Snakes--------------------Birds
BUT
Using fossils, anatomy, molecular comparisons
We see……..
Phylogenetic Fuse
Molecular Data contradicts other data.
Characteristic evolved/originated early in history but did not
proliferate enough to be seen in fossil records until
extinction of dinosaurs.
Human Evolution
9) 25,000 years ago: Other Homo species had gone extinct, leaving only modern
7) 100,000
ago:
3) >3
Human
mya:
brains
Australopithecus
reachedthe
more
afarensis
less the current range of sizes. Early Homo
humans, years
Homo sapiens,
spread
throughout
OldorWorld.
1)
Before
5
mya:
In
Africa,
our
ancestral
lineage
and
the chimpanzee
lineagelived
split.
(“Lucy”)
lived in
Africa.
sapiens lived in Africa.
At the same
time,
Homo neanderthalensis
and Homo erectus
in other
5)
2
mya:
The
first
members
of
the
Homo
clade,
with
their
8)
50,000
years
ago:
Human
cultures
produced
cave
paintings
and
body
adornment,
and
parts of the Old World.
relatively
large
brains,
lived
in Africa.
2)elaborate
Before
4burials.
mya:
The
hominid
Australopithecus
walked their range beyond
constructed
Also,
some
groups
of modernanamensis
humans extended
around what is now Kenya on its hind legs.
Africa.
4) 2.5 mya: Some hominids made tools by chipping stones to form a cutting edge.
6) 1.5 mya: There
Hand were
axes were
used.
Also,
hominids
hadofspread
outliving
of Africa
and into much of Asia
perhaps
four
or more
species
hominid
in Africa.
and Europe. These hominids included the ancestors of Neanderthals (Homo neanderthalensis) in
Europe and Homo erectus in Asia.