Download EVOLUTION

Why do we have DIVERSITY on
Earth?
EVOLUTION
Chapter 15
• Evolution… it’s a theory
− Theory: Well-supported and tested
explanation of phenomena that have
occurred
• What exactly is evolution?
− Change over time
− Process of modern organisms descending
from ancient organisms
Change Over Time
Bill Nye: Evolution
Change Over Time
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Charles Darwin
• Charles Darwin: Born February
12, 1809
Darwin’s Voyage on the
H.M.S. Beagle
• 1831 Darwin set sail from England
on the H.M.S. Beagle as the ship’s
naturalist
• Collected evidence and made
observations that led him to
propose the hypothesis of
EVOLUTION – how life changes
over time
Darwin’s Observations
• Patterns of Diversity
– Observed differences
among organisms
– Organisms were well suited
for the environment they
lived in
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Darwin’s Observations
Darwin’s Observations
• The Galápagos Islands
• Living Organisms & Fossils
– Some fossils looked like
organisms that were still alive
– Other fossils he had ever seen
before
– Islands were close together
but had very different
climates
– Some were hot and dry with
low plants, another was wet
with lots of tall plants
– Darwin was fascinated with
tortoises & iguanas
• Tortoises varied from island
to island
• Their shells and necks were
used to identify which island
they inhabited
Giant Tortoises of the Galápagos
Islands
Jeff Corwin Experience
Pinta
Pinta Island
Marchena
Intermediate shell
Tower
James
Isabel
a
Organisms of the Galapagos
Santa Cruz Santa Fe
Floreana
Hood Island
Hood
Saddle-backed shell
Isabela Island
Dome-shaped shell
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Darwin Presents His Case for
Evolution
The Process of Evolution
• Natural Selection drives evolution
• Natural variation: all
things are different
– Found in all types of
organisms in nature
– Darwin proposed that
much of this variation
could be inherited
The Process of Evolution
• 3 Principles
1. Descent with modification.
2. The struggle for existence.
3. Survival of the fittest.
− Those individuals best suited to their
environment, survive, reproduce… passing on
their traits to their offspring
• Over time, natural selection results in changes
in the inherited characteristics of a
POPULATION.
− These changes increase a species’ ability to
survive in its environment.
1. Descent with Modification
• Species today look differ
from their ancestors
• Each living species has
descended, with changes,
from other species over
time
− Common descent: There is
a common ancestor to all
living things
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2. The Struggle for Existence
• Species compete regularly for:
food, living space, mates and
other necessities
• Some individuals are better
than others in competition
− EX: Cheetahs compete for prey;
faster ones get more prey.
− EX: Males deer fight for territory,
winner lives there and mates with
females – loser sent away
3. Survival of the Fittest
• Fitness: the ability of an
individual to survive and
reproduce in its
environment
− Those better suited for their
environment survive and
reproduce; those poorly
suited will die or have fewer
offspring
• The entire population becomes
better suited for survival over
time.
What are Adaptations?
• An adaptation is a genetically based trait
that helps an organism survive in a
particular environment
− Adaptations may be anatomical structures or
behaviors
− Helps organisms become better suited to
environment… better able to survive,
reproduce, pass on traits
Adaptations Examples WS
How do adaptations benefit
organisms?
What are some examples of adaptions that
you have seen?
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Rock Pocket Mouse
Evolution Packet
Evolution in real-time!
Review
Natural Selection
Simulation
1. What is a theory?
2. What is evolution?
3. What islands did Darwin observe to
develop his theory of evolution?
Will YOU survive??
4. Describe natural selection.
5. What are adaptations?
6. Give an example of an adaptation.
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Example: Survival of the Fittest
PEPPERED MOTHS
• Originally, most peppered moths had light
coloration that camouflaged them against
the light-colored trees and lichens where
they lived
• Industrial Revolution in England = lots of
pollution.
• Thus, trees blackened by soot
Peppered Moth
Activity
Let’s see natural selection in real life!
– Caused light-colored moths to die off due to
predation.
– The dark-colored flourished because of ability
to hide on the darkened trees.
1. A genetic trait that increases and organism’s chance
for survival in a specific environment
2. Gradual changes over long periods of time
1.
Gradual changes over long periods of time
2.
Process in which individuals that are best suited to their
environment live and reproduce most successfully
3. What islands did Darwin observe to develop his
theory of evolution?
3.
A genetic trait that increases and organism’s chance for
survival in a specific environment
4. Process in which individuals that are best suited to
their environment live and reproduce most
successfully
4.
What islands did Darwin observe to develop his theory of
evolution?
5. A well-supported and tested explanation of
phenomena that have occurred
5.
A well-supported and tested explanation of phenomena
that have occurred
6. The ability of an individual to survive and reproduce
in its environment
6.
The ability of an individual to survive and reproduce in its
environment
7. Give an example of an adaptation.
7.
Give an example of an adaptation.
8.
8.
Describe how the peppered moths are an example of
natural selection.
Describe how the peppered moths are an example of
natural selection.
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Darwin vs. Lamarck
Let’s compare their theories on
evolution.
Lamarck’s Theory of Evolution
Selective use of an organ led to change in that organ that
was passed down to the next generation.
1.
Gradual changes over long periods of time
2.
Process in which individuals that are best suited to their
environment live and reproduce most successfully
3.
A genetic trait that increases and organism’s chance for
survival in a specific environment
4.
What islands did Darwin observe to develop his theory of
evolution?
5.
A well-supported and tested explanation of phenomena
that have occurred
6.
The ability of an individual to survive and reproduce in its
environment
7.
Give an example of an adaptation.
8.
Describe how the peppered moths are an example of
natural selection.
Ideas that Shaped Darwin’s Thinking
• Lamarck’s Acquired Characteristics:
organisms could gain or lose traits
during its lifetime by using or not
using organs
– Tendency toward perfection
• EX: Ancestors of birds try to fly,
increase wing size over many
generations and then could fly
Hypothesis was proven incorrect, but
paved the way for other scientists by
observing that organisms are adapted to
their environment.
– Use/disuse
• EX: Birds don’t use wings, lose them
– Traits are inherited
• EX: Large wings passed to offspring
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Can Selection be Artificial?
Artificial Selection
• Yes!
• Nature provides variations within a species and
• Humans have selected for the variations that they
found useful.
• Artificial Selection: We pick what we want to
breed
– We pick the BEST
– Noticed this in farmers, picked largest hogs, fastest
horses to breed
– Breeding based on natural variation
– This created wide ranges of plants and animals that
looked very different from their ancestors
Evidence for Evolution
Who Wants to Live a
Million Years
• Fossil Record
– Physical remains of ancient organisms that show how
things have changed over time
• Fossils show extinct transitional species
connecting ancient species to modern species
Natural Selection leads to change in
populations… EVOLUTION!
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Evidence for Evolution
Evidence for Evolution
• Geographic
Similarities
– Exposed to same
conditions
– Similar animals in
different places came
from different
ancestors
• Homologous Body Structures
– Structures that develop from the same embryonic tissue
but have different mature forms
– Organisms have similar structure and function
– EX: Wing, flipper, and arm—show how things have a
common ancestor
Turtle
Alligator
Bird
Mammals
Typical primitive fish
Evidence for Evolution
• Vestigial organs
– Organs that once had a function, but no more
– EX: Tail bone, Appendix, Wisdom teeth, ear muscles
in humans
Evidence for Evolution
• Similarities in Embryology
– Embryos look similar during early development
– Certain types of cells and tissues develop in a similar order
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Why is Evolution Possible?
• Evolution is made possible because of genetic
variation within a species.
• Sources of genetic variation are:
− Mutations: any change in a sequence of DNA
− Gene Shuffling: crossing over and independent
assortment during meiosis increase variation
• Natural Selection acts on Phenotypes.
Why is Evolution Possible?
• Evolution acts on populations, not on
individuals.
− It’s how beneficial genes become more frequent
over many generations.
• Individual has many offspring because its
phenotype is beneficial -- frequency of genes
in a gene pool increases.
• If an individual does not reproduce -- genes
removed from gene pool.
How are New Species Created?
• Speciation occurs when there is Reproductive
Isolation.
− When members of two populations do not
interbreed and produce fertile offspring
• 3 Types of Reproductive Isolation
1. Behavioral Isolation
2. Geographic Isolation
3. Temporal Isolation
Reproductive Isolation
• Behavioral Isolation: two
populations can interbreed
but have different courtship
rituals or other behavior
− EX: Two birds whose habitats
overlap don’t mate; mating
songs are different.
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Reproductive Isolation
• Geographic Isolation:
two species are separated
by geographic barriers
such as rivers, mountains,
or bodies of water.
Giant Tortoises of the Galápagos
Islands
Pinta
Pinta Island
Marchena
Intermediate shell
− EX: Islands separating
Galapagos Tortoises and
Finches
Tower
James
Isabel
a
Santa Cruz Santa Fe
Floreana
Hood Island
Hood
Saddle-backed shell
Isabela Island
Dome-shaped shell
Reproductive Isolation
• Temporal Isolation: two or more species
reproduce at different times
− EX: Orchids in the rainforest-each species
releases pollen at different times so they cannot
pollinate one another
Galapagos Finches
• The finches of the Galapagos
provide a key example for
speciation.
1. Founding species of finch
arrives on different islands.
2. The species of each island
are geographically
separated causing
reproductive isolation.
3. Each population adapts
differently and speciation
occurs through natural
selection.
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