Bio 2 Plant and Animal Biology
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Bio 2 Plant and Animal Biology
Evolution
Evolution as the
explanation
for life’s unity
and diversity
Darwinian Revolution
Two main Points
– Descent with
Modification
– Natural Selection
Biological Species
A group of populations whose
members have the potential to
interbreed in nature and produce viable,
fertile offspring
Two Patterns of Evolutionary Change
Anagenesis
Cladogenesis
Allopatric Speciation
Evidence of Allopatric Speciation
Allopatric Speciation
Allopatric Speciation
1. Small Population
2. Isolation
3. Different
Environmental
Conditions
Sympatric Speciation
Autopolyploidy
– Examples:
Maidenhair Fern
Bufo pewzowi
Cell
division
error 2n=6 Tetraploid Cell
4n=12
2n
2n
New Species
(4n) Gametes produced
by Tetraploid
Sympatric Speciation
Allopolyploidy
– Examples:
Triticum aestivum
Gray Treefrog
Hybrid Zone
Hybrid Zone
Hybrid Zone
Over time
– Reinforcement
Strengthening of reproductive barriers
– Fusion
Weakening of reproductive barriers
– Stability
Continued production of hybrid
individuals
Adaptive Radiation
The emergence of
numerous species
from a common
ancestor introduced
into an environment,
presenting a
diversity of new
opportunities and
problems
Adaptive Radiation (Silversword Alliance - Tarweed)
Macroevolution: Evolutionary Change on a
Grand Scale Punctuated
Equilibrium
Gradualism
Time
Gradualism
Also called
“Neodarwinism”
Small changes
over time
Supporter: Ernst
Mayr
Gradualism
Populational - new traits become
established in a population by
increasing their frequency from a small
fraction of the population to the
majority
Gradualism Phenotypic –
New traits, even
those that are
strikingly
different from
ancestral ones
are produced in
small increments
Gradualism
Phyletic - On a
geological time
scale, there are
intermediate forms
connecting the
phenotypes of
ancestors and
descendents
Punctuated Equilibrium Supporters: Niles
Eldredge & Stephen J. Gould
Speciation occurs in episodic events – large periods of time with little change and short periods of time with large changes
Macroevolution through many Speciation Events
Macroevolution through many Speciation Events
Evolutionary Novelties
Evolution of Genes that control
development
– Changes in Spatial Pattern
– Changes in Rate and Timing
Origin of Evolutionary Novelty
Most novelties
are modified
versions of older
structures
– Exaptation -
preadaptation
Evolution of Genes that Control Development
Julian Huxley - Modern
Synthesis
– Gradual evolution can
be explained by small
genetic changes that
produce variation
which is acted upon
by natural selection
Evolution of Genes that Control Development
Julian Huxley - Modern
Synthesis
– The evolution at
higher taxonomic
levels and of greater
magnitude can be
explained by long
periods of time
Evolution of Genes that control Development
Forms change
Natural Selection is
the force driving
change
How did it occur?
Evolution of Genes that control Development
“Evo-devo” – How
does it occur?
Evolution of Genes that control Development
“Evo-devo” - Tool-kit
of master genes
Changes in Spatial Pattern
Homeotic Genes
(Hox Genes)
position information
Changes in Spatial Pattern
Changes in Spatial Pattern
Homeobox
Changes in Spatial Pattern
Changes in
expression
patterns of
four Hox
genes over
time
Changes in Rate and Timing
Allometric Growth
the variation in
the relative rates of
growth of various
parts of the body
Heterochrony - evolutionary change in the
timing or rate of development
Changes in rate and timing
Changes in rate and timing
Paedeomorphosis - retention of juvenile
features in an adult
Changes in rate and timing
Paedeogenesis - sexual maturity in a larval
form
Evolutionary Trends
Evolutionary
trends are
not goal
oriented
The Tree of Life
Biological Diversity
The Fossil Record
The Fossil Record
The Fossil Record
Sedimentary Rocks Hard Parts
The Fossil Record
Minerals replacing
organic material
Organic Material
The Fossil Record
Casts Trace Fossils
The Fossil Record Entire Organisms
Dating Fossils
Absolute Dating (half-life)
Relative Dating
Precambrian
(Archaean)
Origin of Earth
(4.6 bya)
Oldest known
rocks on
Earth’s surface
(3.8 bya)
History of the Earth
Precambrian
(Archaean)
Oldest
Prokaryotes (3.5
bya)
History of the Earth
Precambrian
(Archaean)
Oxygen (2.7
bya)
Precambrian (Proterozoic) Oldest
Eukaryotes
(2.1 bya)
Diversification
of Multicellular
Eukaryotes
(542-635 mya)
Paleozoic Era - Cambrian Period (488 – 542 mya)
Cambrian
Explosion
- Origin of
most
modern
animal
phyla
Paleozoic Era - Ordovician Period
(488 – 444 mya)
Origin of
land plants
First
arthropods
on land
First
jawless fish
First Fungi
Paleozoic Era - Silurian Period
(444 – 416) First jawed fish
First vascular plants
Diversity of early vascular plants
Paleozoic Era - Devonian Period (416 – 359 mya)
Age of Fishes
First Amphibians
First Insects
Paleozoic Era - Carboniferous Period
(359 – 299 mya)
Vascular Forests
First Seed Plants
Amphibians
Abundant
First Reptiles
Paleozoic Era - Permian Period (299 – 251 mya) Radiation of
Reptiles
Origin of mammal-
like Reptiles
Most modern orders
of insects
Largest Extinction
Gymnosperms
dominant
Radiation of
Dinosaurs
First Mammals
and Birds
Mesozoic Era - Triassic Period
(251 – 199.6 mya)
Dinosaurs Dominate
Gymnosperms Dominate
Mesozoic Era - Jurassic Period
(199.6 – 145.5 mya)
Flowering
Plants
Appear
Dinosaurs
Disappear
at End of
Period
Mesozoic Era - Cretaceous Period (145.5 – 65.5 mya)
Cenozoic Era (Age of Mammals)
Quaternary Period (2.6 mya – Present)
Neogene Period (23 – 2.6 mya)
Paleogene Period (65.5 - 23 mya)
Adaptive
Radiation of
Mammals,
Birds, and
Insects
Paleogene Period -
Paleocene Epoch
Angiosperm
Dominance
Most Modern
Mammal Orders
Paleogene Period - Eocene Epoch
First Primates Paleogene Period -
Oligocene Epoch
Neogene Period - Miocene Epoch
Continued Radiation
of Mammals and
Flowering Plants
Earliest direct
human ancestors
Bipedal human
ancestors appear
Neogene Period - Pliocene
Epoch
Ice Ages
Homo genus
appears
Quaternary Period – Pleistocene Epoch
Historic
Time
Quaternary Period Recent (Holocene) Epoch
Continental Drift and
Plate Tectonics
Plate Tectonics
Plate Tectonics
Earth’s History
Pangaea (245 mya)
Pangaea began to
break up (180 mya)
– Laurasia
– Gondwana
Mass Extinctions Ordovician
(440)
Devonian (365)
Permian (245)
Triassic (210)
Cretaceous
(65)
K-T Boundary
Chicxulub Crater -
Caribbean Sea near
the Yucatan
Peninsula of Mexico
Tree of Life
Systematics
The study of
biological
diversity in an
evolutionary
context
Systematic Tools
Molecular Comparisons
– usually (rRNA or
mtDNA)
DNA-DNA
Hybridization
Restriction maps
DNA Sequence
analysis
Phylogenetic Groupings
Monophyletic
– ancestor and all its descendants
Phylogenetic Groupings
Paraphyletic
– ancestor with some but not all its
descendants
Phylogenetic Groupings
Polyphyletic
– two different ancestors
Phylogenetic Groupings
Similarities
Homology
– likeness attributed
to shared
ancestry
Similarities
Analogy
– likeness due to
similar ecological
roles and natural
selection due to
convergent
evolution
Molecular Homoplasy
Analogous species that have similar
DNA sequences that evolved
independently in two species
Ontogeny Recapitulates Phylogeny (Ernst Haeckel)
Ontogeny – individual
development
Recapitulates –
repeats
Phylogeny –
evolutionary descent
The Science of Systematics
Phenetics
– based on a number of similarities and
differences
– does not take into account homology
or analogy
– all groupings
Classical Evolutionary Systematics
George Gaylord Simpson
The Science of Phylogenetic Systematics
Classical Evolutionary Systematics
– most commonly used up until recently
– based on shared homologous
structures
– takes into account the amount of
adaptive evolutionary change
(novelties)
– Monophyletic and paraphyletic
groupings
The Science of Systematics
Cladistics (Phylogenetic Systematics)
– based on shared homologous structures
– only monophyletic groupings
Will Hennig
The Science of Phylogenetic Systematics
Cladistic Assumptions
1. Monophyletic
2. Descent follows a bifurcating
pattern
3. Changes in characteristics occur
in lineages over time
Cladistics Synapomorphies:
Shared ancestral
characters
Plesiomorphies:
Shared Primitive
characters
Apomorphies:
Shared derived
characters
Phylograms
Ultrametric Trees
Cladistics
Cladistics
Cladistics
Molecular Clock
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