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