Transcript Chapter 23 - Cladograms

Chapter 23
Systematics: study of
biological
diversity in evolutionary context
Phylogeny: evolutionary history of
species or group of related species
Best place  sedimentary rock
(forms in strata)
Geologic Time
Scale
 Sequence of historical periods
 Four eras (distinct time in Earth’s
life broken by periods of mass
extinction)
Precambrian
Paleozoic
Mesozoic
Cenozoic
 Eras  Periods  Epoch
 Gives us relative ages of fossils
Absolute dating: age in years
 Radiometric dating: Half-life (time it
takes for 50% of radioactive isotopic
amount of original sample to decay)
 Racemization (chemical conversion):
rate of decay of L-amino acids to Damino acids (issue – temp sensitive)
Pangaea – all land masses become
supercontinent (245 mya)
 Major
biological
impact
Pangaea split 180 mya
Fossil record helps
support this
Permian – 250 mya
 90% marine animals lost
 Radical environmental changes
(Pangaea, massive volcanic
eruptions)
 Extinctions
Cretaceous – 65 mya
 50% marine species, dinosaurs
 Comet or asteroid?
– 18th century
 Binomial nomenclature
2-name system (genus & species)
Poecilia reticulata (guppy)
Homo sapiens (“wise man”)
Carolus Linnaeus
 Hierarchial classification
Levels of grouping organisms
Name at any level – taxon
Domain  Kingdom  Phylum
 Class  Order  Family 
Genus  Species

Phylogenetic
tree: used to
show
relationships
of related
organisms
Cladogram: phylogenic diagram where
evolutionary relationships are shown
 Each “branch” – clade
Divergence of species
from a common
ancestor
Represents ancestral species & all
of its
descendents (monophyletic)
 Cannot be polyphyletic or
paraphyletic
Determine analogy from homology
 Homology: likeness due to shared
ancestry
 Analogy: likeness due to similar
evolutionary factors (convergent
evolution)
 Greater number of homologous
parts  more closely related
 More complex two similar structure
are  more closely related
Niche
Burrower
Placental Mammals
Australian Marsupials
Mole
Marsupial mole
Anteater
Numbat
Anteater
Nocturnal
insectivore
Mouse
Climber
Marsupial mouse
Spotted cuscus
Lemur
Glider
Stalking
predator
Chasing
predator
Sugar glider
Flying
squirrel
Ocelot
Tasmanian cat
Wolf
Tasmanian “wolf”
Ocotillo – in the
Southwestern part of
North America
Alluauida – Madagascar
Alluauida – Madagascar
Identify shared derived characters
 Evolutionary novelty unique to a
particular clade (such as hair for
mammals)
 Different from shared primitive
characters, which were present before
the new clade
Cladogram
Construction
Perform outgroup comparison
 Differentiate shared primitive characters
from shared derived ones
 Compare related species (ingroup) to a
non-related species (outgroup) and
determine which characters are present &
which are absent
DNA, genes, proteins
 Called molecular systematics
 More specific than previous
methods
 Make cladogram where branch
points are mutations in DNA
 May have trouble comparing if
mutations changed DNA length
Human
Macaque
Dog Bird
Frog
Lamprey
Comparative hemoglobin structure
8
0
32
45
67
125
10 20 30 40 50 60 70 80 90 100 110 120
Number of amino acid differences between  compare common genes
hemoglobin (146 aa) of vertebrate species and that
of humans C (respiration)
 cytochrome
 hemoglobin (gas exchange)
When making a cladogram, make
one that is simple & has least # of
evolutionary events
 Keep it simple  parsimony
These trees are hypotheses
Way to put origin of
taxonomic
groups into actual time
 Based on obs. that some
genomes evolve at constant rates