Lecture

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Lecture 1 Darwinian Evolution
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Key Concepts

• Evidence for evolution
• Darwins theory
• The Modern Synthesis

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Spiritual vs. IntellectualDifferent, but not
necessarily in conflict
The human emotional experience
The human intellectual experience
The Bible tells us how to go to Heaven, not how
the heavens go Galileo
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Reality CheckThe worlds major religions and
the dominant religion in the worlds four most
populous countries
SOURCE National Geographic, December 2007
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There are many equally valid ways to go to
Heaven

• We rely on our religious texts for moral,
  emotional and spiritual guidance
• We rely on science and other intellectual
  pursuits to gain knowledge about the natural world

There need be no conflict in these different ways
of thinking and learning
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Defining Evolution

• A process of change over time
• Cannot deny that this occurs
• Evidence is overwhelming
• Historical within the span of recorded human
  history
• Fossils the very long term geological record
• Comparative morphology and anatomy
• Biogeography the geographic distribution of
  species
• The unity of life

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Historical Evidence observed character
displacement Changes in beak size recorded over
about 2 decades after a natural migration event
Big-beaked invader
Image finches on the Galapagos
Photographs by B. Rosemary Grant/Science, 2006
Resident species shifted to smaller beak size
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All of agriculture is based on human selection
events

• The domestication of grass 12,000 years ago
• Led to the first cultural shift in human
  civilization
• Nomadic hunter-gather tribes ? villages based on
  agricultural production
• Other plants and animals as well.

Image wheat
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Artificial Selection Brassica oleracea in all
its forms
Image cabbage, kale, cauliflower, broccoli,
Brussels sprouts
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Farm Animals different breeds
Images different breeds of cattle and chickens
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Cats and DogsA great dane is the same species as
a toy poodle!
Images different breeds of cats and dogs
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The development of pesticide resistance

• Resistance to insecticides, herbicides,
  antibiotics..
• All natural responses to human generated changes
  in the environment

Diagram development of pesticide resistance due
to use of insecticides
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Defining Evolution

• A process of change over time
• Cannot deny that this occurs
• Evidence is overwhelming
• Historical within the span of recorded human
  history
• Fossils the very long term geological record
• Comparative morphology and anatomy
• Biogeography the geographic distribution of
  species
• The unity of life

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The fossil record extends back BILLIONS of years
Images fossils of plants and fish
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Most form in marine sediments
Diagram formation of sedimentary rocks with
fossils embedded
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Fossil substrates can you think of others???
Images other fossil substrates
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Formation of sedimentary rocks is not uniform in
time or space
Same diagram as 15
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Critical Thinking

• The formation of sedimentary rocks is not uniform
  in time or space
• Why not???

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Critical Thinking

• The formation of sedimentary rocks is not uniform
  in time or space
• Why not???
• Dynamic processes!
• Geological activity
• Climate
• Depositional environments

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Formation of sedimentary rocks is highly dynamic

• Varies with geological activity
• Tectonic movements, mountain building, erosion
• Varies with climate
• Rain, wind, freeze/thaw cycles, water temperature
  all affect erosion and sedimentation
• Varies with the depositional environment
• Finer sediments in still water, coarser sediments
  with more wave action or other energy

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The earths crust is very dynamic
Diagram dynamic geological processes tectonic
movements, mountain building, erosion
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Formation of sedimentary rocks is highly dynamic

• Varies with geological activity
• Tectonic movements, mountain building, erosion
• Varies with climate
• Rain, wind, freeze/thaw cycles, water temperature
  all affect erosion and sedimentation
• Varies with the depositional environment
• Finer sediments in still water, coarser sediments
  with more wave action or other energy

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Climate is naturally dynamic on a geological time
scale
Graph benthic carbonates analogous to climate
change over the past 5 million years
Benthic carbonates parallel atmospheric
temperature changes
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Critical Thinking

• How could water temperature affect the formation
  of sedimentary rocks???

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Critical Thinking

• How could water temperature affect the formation
  of sedimentary rocks???
• Limestone is a sedimentary rock that is formed
  from the tiny shells of marine organisms
• The abundance of these organisms is partially
  dependent on water temperature

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Formation of sedimentary rocks is highly dynamic

• Varies with geological activity
• Tectonic movements, mountain building, erosion
• Varies with climate
• Rain, wind, freeze/thaw cycles, water temperature
  all affect erosion and sedimentation
• Varies with the depositional environment
• Finer sediments in still water, coarser sediments
  with more wave action or other energy WHY???

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Play with the ocean

• In high energy environments (waves) only the
  heaviest sediments can settle
• Coastal environments produce sandstones
• In off-shore environments (no waves) finer
  sediments can settle
• Off-shore environments produce siltstones,
  slates, limestones

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Sediment size depends on the energy level at the
site of deposition
Diagram of different depositional environments
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Formation of sedimentary rocks is highly dynamic

• THUS sediments tend to be deposited in
  identifiable layers
• THUS organisms trapped in sediments form a time
  sequence
• The earliest organisms are in the bottom layers
  and the most recent organisms in the upper layers

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The Grand Canyon a time sequence
Image the Grand Canyon
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Formation of sedimentary rocks is highly dynamic

• THUS sediments tend to be deposited in
  identifiable layers
• THUS organisms trapped in sediments form a time
  sequence
• The earliest organisms are in the bottom layers
  and the most recent organisms in the upper layers
• Dating these fossils reveals the history of change

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Study the geological time scale its the
history of life on earth! Use a search engine to
find the geological time scale
The geological time scale
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Of course the fossil record is incomplete!

• Organisms must be trapped in the right place
  under the right conditions a rare event
• Fossils must survive geological processes such as
  subduction, metamorphosis and erosion
• Fossils must be found!
• Have you ever found a fossil???
• But what we do have is irrefutable evidence of
  change over time

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Fossil Evidence Shows Progression Over Time new
species.
Diagram evolution of elephant lineages
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.new traits.
Diagram limbs developing from bony fins in
tetrapods
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.transitional forms.
Diagram transition from bony fins to limbs
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Defining Evolution

• A process of change over time
• Cannot deny that this occurs
• Evidence is overwhelming
• Historical within the span of recorded human
  history
• Fossils the very long term geological record
• Comparative morphology and anatomy
• Biogeography the geographic distribution of
  species
• The unity of life

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Comparative morphology homologous structures
are derived from a common ancestor
Diagram forelimbs of various mammals showing
identical bone structure with variation in bone
size
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Fish
Salamander
Tortoise
Chicken
Pig
Cow
Rabbit
Human
Stage of Development
Early
Diagram similarities in the embryos of a wide
variety of vertebrates
Later
Strickberger, 1996
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Images orchid floral structure
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Comparative morphology vestigial traits

• Structures that are physically or functionally
  reduced but clearly similar to functional
  structures in related organisms
• Tiny limb bones in some snakes and aquatic
  mammals
• Non-flying wings in ostriches emus, kiwis,
  penguins
• Blind eyes in cave-dwelling animals
• Vestigial tails in humans

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Defining Evolution

• A process of change over time
• Cannot deny that this occurs
• Evidence is overwhelming
• Historical within the span of recorded human
  history
• Fossils the very long term geological record
• Comparative morphology and anatomy
• Biogeography the geographic distribution of
  species
• The unity of life

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Biogeography Darwin observed patterns of
species distribution during his voyage on the
Beagle
Diagram the voyage of the Beagle
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Sloths found only in South America, even though
similar habitats exist on other continents
Image modern and fossil sloths
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Marsupials almost restricted to
Australia though convergent evolution has
resulted in many similar eutherian mammals on
other continents
Diagram of marsupial and eutherian mammals
showing similar forms
Convergent evolution similar traits in
unrelated organisms that evolved under similar
selection pressures.more later
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The Galápagos and other volcanic islands Many
closely related endemic species.that are similar
to those found on the closest mainland Darwins
conclusion species migrated and evolved new
adaptations in their new home
Diagram of Darwins finch lineages
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Defining Evolution

• A process of change over time
• Cannot deny that this occurs
• Evidence is overwhelming
• Historical within the span of recorded human
  history
• Fossils the very long term geological record
• Comparative morphology and anatomy
• Biogeography the geographic distribution of
  species
• The unity of life

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Uniformity and Diversity same DNA, same ATP,
same amino acids, same membranes, same aerobic
respiration.
Image frog in the center of a bromeliad
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Critical Thinking

• What is the implication of this uniformity in the
  basic building blocks of life, even though there
  are many millions of organisms both extant and
  extinct???

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Critical Thinking

• What is the implication of this uniformity in the
  basic building blocks of life, even though there
  are many millions of organisms both extant and
  extinct???
• These structures and processes emerged at the
  very beginning of life on this planet and have
  been conserved in all organisms throughout
  evolutionary history

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Defining Evolution

• A process of change over time
• Cannot deny that this occurs
• Evidence is overwhelming
• Historical within the span of recorded human
  history
• Fossils the very long term geological record
• Comparative morphology and anatomy
• Biogeography the geographic distribution of
  species
• The unity of life

Step 1 accepting that evolution occurs.Step
2 HOW???
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Historical Context The development of ideas about
biological evolution and the age of the earth
began in the 1700s Darwin was just the first
to publish!
Timeline the development of thought on evolution
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Darwins voyage on the Beagle, 1831-1836..publica
tion of his theory, 1859
Map the voyage of the Beagle
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Darwins Theory of Evolution by Natural
Selectionbased on observation logical inference

• OBSERVATION 1 all species have the
  reproductive potential for exponential population
  growth
• OBSERVATION 2 populations tend to remain
  stable OBSERVATION 3 environmental resources
  are limited
• INFERENCE 1 excess of offspring leads to a
  struggle for existence
• OBSERVATION 4 significant variation exists
  between individuals of the same species
• OBSERVATION 5 some variation is heritable
• INFERENCE 2 individuals that are best adapted
  to their environment contribute more offspring to
  the next generation differential reproductive
  success Darwins natural selection
• INFERENCE 3 TIME X CHANGE DIVERSITY

Dont panic this is just a summary slide for
you to look at later
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Observation 1 All species have the potential
for exponential population growth
Images examples of high reproductive potential
in various organisms
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Observation 2 Populations tend to remain
stable (though sometimes within a fluctuating
range) not exponential
Graphs examples of actual population growth
patterns
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Observation 3 Environmental resources are
limited
Image lynx chasing rabbit
food.
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water.
Image desert landscape
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habitat.
Images various animals in habitat
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Inference 1 Excess offspring in a
resource-limited environment leads to a struggle
for existence
Image resource competition between aquatic
plants
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Observation 4 Variation exists in all natural
populations
Diagram natural variation in beetles
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Image natural variation in plants
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Image natural variation in mollusks
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Images natural variation in humans
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Observation 5 Some variation is heritable
Images heritable variation in various animals
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Inference 2 Best adapted individuals reproduce
the mostDifferential Reproductive Success!!!
Image polar bears fighting
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Inference 3 Darwins Big One
Over long periods of time and many generations
the incremental results of differential
reproductive success will lead to divergence
between populations in different environments and
eventually to the development of new species
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Key Conclusion Small changes over long periods
of time result in adaptations to different
environments and to the emergence of new species
Image orchid mantis
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Same as 68
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Same as 68
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Images additional cryptic animals through
slide 78
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Critical Thinking

• What other testable explanation is there for an
  insect or other animal that evades predation by
  mimicking its habitat???
• How else might this cryptic form and coloration
  benefit the animal???

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Critical Thinking

• What other testable explanation is there for an
  insect or other animal that evades predation by
  mimicking its habitat???
• None
• How else might this cryptic form and coloration
  benefit the animal???

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Critical Thinking

• What other testable explanation is there for an
  insect or other animal that evades predation by
  mimicking its habitat???
• None
• How else might this cryptic form and coloration
  benefit the animal???
• More likely to catch their own prey items

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Darwin originally predicted gradual speciation
from a common ancestor..

• Now we know that abrupt changes are also possible
  
• Also, some gradual changes may not be recorded in
  the fossil record

Diagram mammal lineages
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Questions Remain

• We dont, and may never, know exactly how life
  originated on this planet
• But we do have a pretty good explanation for how
  diversity developed and why diversity changes
  over time
• Conditions change
• Organisms adapt

Images more cryptic animals same on next slide
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Questions Remain

• We dont, and may never, know exactly how life
  originated on this planet
• But we do have a pretty good explanation for how
  diversity developed and why diversity changes
  over time
• Conditions change
• Organisms adapt

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The Modern Synthesis

• Darwins concepts of natural selection and
  differential reproductive success leading to
  adaptations and speciation
• Mendels work on heredity and hypothesis of a
  particulate method of hereditary transfer
• Microscopic revelation of chromosomes as that
  particle in the late 1800s early 1900s
• Discovery of the structure of the DNA molecule in
  the early 1950s

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The Theory of Evolution
A comprehensive body of knowledge that describes
a known fact of nature
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Key Concepts

• Evidence for evolution
• Darwins theory
• The Modern Synthesis

Questions???