Transcript 1. Divergent Evolution

Do Now
• 1. What about the skeleton in
the photo reminds you of a
living thing?
• 2. What about the skeleton
reminds you of a nonliving
thing?
• 3. What might studying this
skeleton help you to learn
about living things?
• 4. What might be some
benefits of studying living
things?
Answers
• 1/2. The skeleton is made of organic materials and was
once part of a living thing, but the skeleton cannot
move on its own, reproduce, or grow.
• 3. Studying the skeleton could reveal how the internal
structure of a living thing is supported, how bones are
formed, or how living things grow.
• 4. The study of living things can help people to
understand themselves and might lead to practical
benefits such as cures for disease, improvements to
the environment, and more efficient use of Earth’s
resources.
Evolution
Chapters 14 & 15
Objectives
• To understand what evolution is.
• To explain spontaneous generation,
theory of biogenesis and the primordial
soup hypothesis.
What is Evolution?
• The change in living organisms over time!
The Origin of Life: Early Ideas
14.2
• Where do living things come from??
• Spontaneous Generation:
– The idea that life arises from non-life
• Ex: mud gives rise to worms?? We can make mice
out of hay??
• Fransisco Redi:
– An Italian scientist
– Tested the idea of spontaneous generation.
What happens when you leave
meat out for a long time?
Redi’s Experiment- 1668
• He placed meat in both an open container,
and a closed container to see what
happened…
Redi’s Conclusions
• Maggots come from
FLIES, not meat.
• Life must come from
life, not spontaneous
generation right?
– Not completely
rejected until later
on…
Now what?
• Louis Pasteur
experimented with the
“Theory of
biogenesis”.
• Theory of
Biogenesis:
– Only living organisms
can produce other
living organisms.
Pasteur’s Experiment
• Tested the idea of spontaneous generation
again
• Nutrient rich broth was exposed to air but
not dust and spores
Pasteur’s Conclusion
• Living organisms
must be able to enter
the broth in order to
grow
• Living things do NOT
spontaneously
generate
What about LIFE?
• So we know that life can only come from
life… but where did the original life come
from???
• What was in the Earth’s atmosphere??
Volcanoes!!
• Gases were expelled
from volcanoes
–
–
–
–
–
–
–
–
–
Water Vapor (H2O)
Carbon Dioxide (CO2)
Sulfur Dioxide (SO2)
Carbon Monoxide (CO)
Hydrogen Sulfide (H2S)
Hydrogen Cyanide (HCN)
Nitrogen (N2)
Hydrogen (H2)
NO OXYGEN!!!!!!!
How do we KNOW that was what the
atmosphere was made of?
• Miller and Urey!
– Created an experiment to show how the first
molecules of life could be formed…
– Water + hypothesized gases + electric discharges
(boiled) (methane, amonia,
(energy: like lightning)
hydrogen)
Amino acids & other organic compounds!
Miller and Urey’s Conclusions
• Primordial soup
hypothesis:
– early hypothesis about the
origin of life
– simple organic molecules
could be made from
inorganic compounds.
• Primary Energy
Sources:
– UV light from the Sun
– Electric discharge in
lightning
Overview of Evolution…
Cellular Evolution
• Scientists hypothesize that the first cells
were prokaryotes
• Modern prokaryotes called archaea are
the closest relatives of Earth’s first cells.
• Archaea are autotrophic
• They do not obtain their energy from the
Sun.
Photosynthesizing Prokaryotes
• Photosynthesizing
prokaryotes evolved
not long after the
archaea.
• Prokaryotes, called
cyanobacteria, have
been found in rocks
as old as 3.5 billion
years.
Conclusion Activity
• State the scientist who came up with
different theories:
• 1. Discovered part of cell theory.
• 2. Created early earth environment to test
hypothesis.
• 3. First to discover that spontaneous
generation was false.
• 4. Worked with maggots and meat
• 5. Discovered primordial soup hypothesis.
Do Now
• Who were the 3 scientists we talked
about and what did each of them do?
Objectives
• Determine how cells developed.
• Explain the endosymbiont theory.
• List and describe the steps of natural
selection.
Think back…
How are prokaryotes and eukaryotes
different?
Prokaryotes
Eukaryotes
How did we get Eukaryotes?
“Endosymbiont Theory”
• Eukaryotic cells lived in association with
prokaryotic cells.
• Relationship between the cells became
mutually beneficial, and the prokaryotic
symbionts became organelles inside
eukaryotic cells.
• This theory explains the origin of
chloroplasts and mitochondria.
Endosymbiont Theory
Animation
• http://highered.mcgrawhill.com/sites/9834092339/student_view0/
chapter4/animation_-_endosymbiosis.html
Evidence of Endosymbiosis
• Mitochondria have circular DNA like bacteria
• Replicates like bacteria separate from the host
cell
• DNA codes for proteins that are similar to
bacterial proteins
• Mitochondria make their own proteins
• Mitochondria have two membranes (one from
the host cell and one from their own cell
membrane)
Fast forward a couple billion years…
Who is this guy?
Charles Darwin
 Darwin was a Naturalist
 He collect biological and geological
specimens during his travels on his ship
the HMS Beagle.
Darwin and the Galapagos Islands
 Darwin collected different birds on each of the
4 islands he went to. (mostly finches)
 discovered that each island had their own,
slightly different varieties of birds.
 Populations from the mainland changed after
reaching the Galápagos.
 Darwin hypothesized that new species
could appear gradually through small
changes
So What?
Darwin Concluded…
 Humans could
change species by
artificial selection,
then the same
process could work in
nature.
• Ex) Corn Selection
Other examples of “artificial
selection”
Natural Selection
• Some competitors in the struggle for
existence are better equipped for
survival than others; those less
equipped die.
Natural Selection

1) Individuals in a population show
variations.
Natural Selection
• 2) Variations can be inherited.
Natural Selection
• 3) Organisms have more offspring than
can survive on available resources.
Natural Selection
• 4) Variations that increase reproductive
success will have a greater chance of
being passed on.
Use the following example
and explain the four parts of
natural selection.
• A male peacock has bright colored feathers to
attract a mate
– 1. Variation
– 2. Inherited
– 3. More offspring are produced than can survive
– 4.Varations with Reproductive Success
Go through the 4 steps of natural
selection with these moths…
1. What did
Darwin infer from
his observations of
artificial selection?
A. Animal breeders could create new species.
B. A similar process could work in nature.
C. Reproductive success could be increased.
D. Variation in a species could be produced.
2. What is the
A. They mean the same thing.
B. Evolution works against natural selection.
C. Evolution explains how natural selection works.
D. Natural selection explains how evolution works.
relationship
between natural
selection and
evolution?
A. The different tortoises were different species.
why the tortoises on B. The environment on each island was different.
the different islands C. Each type of tortoise could survive only on its
own island.
of the Galápagos
D. They arrived on the islands from different
had slightly different continents.
3. Which explains
variations in their
shells?
Think – Pair - Share
• Brainstorm- How do scientists know that
evolution occurred?
• What is some evidence for evolution?
15.2 Evidence for Evolution
•
•
•
•
1. Fossil Evidence
2. Evidence from Anatomy
3. Embryology
4. Biochemistry
– Genetic Evidence
• 5. Geographic Distribution
• 6. Direct Observation
1. Fossil Evidence
 Fossils provide a record of species that
lived long ago.
 Fossils show that ancient species share
similarities with species that now live on
Earth.
2. Evidence from Anatomy
• A. Homologous Parts
 Anatomically similar structures inherited from
a common ancestor are called homologous
structures.
2. Evidence from Anatomy
• B. Vestigial Structures
 Structures that are the reduced forms of functional
structures in other organisms.
 Evolutionary theory predicts that these features will
become smaller over time until they are lost.
2. Evidence from Anatomy
• D. Analogous Structures:
– Can be used for the same purpose (look
similar), but not inherited from a recent
common ancestor
– Ex. Wings of an eagle and beetle
Think – Pair - Share
• Compare and contrast analogous and
homologous structures.
• List 3 examples of each not mentioned in
class.
3. Embryology
• Vertebrate embryos exhibit homologous
structures during certain phases of
development
• Become totally different structures in the
adult forms.
Do Now
• What are homologous structures? Give an
example
• What are analogous structures? Give an
example
• What are vestigial structures? Give an
example
4. Biochemistry
• Common ancestry can be seen in the
complex metabolic molecules that many
different organisms share.
– Ex. Hemoglobin, amino acids
4. Biochemistry – Genetic
Evidence
• Mutations are the
raw material for
evolutionary
change
• Genetics can tell us
how different
groups of
organisms are
related back
through time.
5. Geographic Distribution
• The distribution of plants and animals
that Darwin saw first suggested
evolution to Darwin.
• Ex. Animals on S. America mainland
were more similar to other S. American
animals than to animals living in
comparable environments in Europe
6. Direct Observations
• Some evolution takes place more
rapidly than others
• Ex. evolution of drug resistant
bacteria. This type of evolution can
be directly observed by scientists.
Conclusion Activity
• Match the following with the type of evidence
1. The HIV virus is constantly
changing and evolving.
2. All living things share the
same amino acids
3. Evidence that Dinosaurs
were once on earth
4. Humans and Chimps have
similar bone structures
5. The fetus of a pig and dog
go through similar
A. Fossil Evidence
B. Biochemical Evidence
C. Embryology
D. Direct Observation
E. Evidence from
Anatomy
Do Now
• What is an adaptation?
• Explain how adaptations are shaped by
natural selection.
Adaptations
• A trait shaped by natural selection that increases
an organism’s reproductive success
• Fitness:
– How well an organism is suited for an environment
– How well an organism can pass it’s traits to the next
generation
Types of Adaptation
• Camouflage:
– Allows an organism to become almost
invisible to predators
Mimicry
 One species evolves to resemble another
species.
Western coral snake
California kingsnake
Speciation
• A species is a group of organisms that can
interbreed and produce fertile offspring in nature.
• interspecies breeding can sometimes produce
offspring that are infertile such as horses and
donkeys producing mules
• Speciation: the development of a new species.
DO NOW
• Work on the worksheet as a review of the
evidence of evolution.
15.3 Types of Natural Selection
• Stabilizing Selection
– Eliminates extreme
expressions of a trait
because the average
expression increases
survival
• Ex: most human babies
are born with average
weights
Directional Selection
• This happens when an extreme version of
a trait makes an organism more fit.
– Ex: when something happens to change the
environment of an organism such as a
drought.
Disruptive Selection
• A process that splits a population into two
groups because the organisms that
express extreme traits survive and the
average trait does not.
– Ex: Snake coloration
Sexual Selection
• Frequency of a trait is based on the ability
to attract a mate.
• Males evolve with threatening
characteristics or bright colors to attract
females.
Sexual Selection
• Peacock Video
Get with a partner!
• Types of Natural Selection worksheet
Patterns of Evolution
1. Divergent Evolution
- Adaptive radiation
- Reproductive Isolation
2. Convergent Evolution
3. Coevolution
1. Divergent Evolution
• When one species evolves into two or
more species with different
characteristics
– One type of Divergent evolution is called
adaptive radiation.
Adaptive Radiation
• Can occur in a relatively short time
• One species gives rise to many
different species in response to the
creation of new habitat or some other
ecological opportunity
1. Divergent Evolution (cont.)
• Divergent evolution can sometimes lead to
reproductive isolation.
• Prevents two species from mating.
• It can be caused by:
– 1. geographic isolation (allopatric speciation)
– 2. genetic mutations (sympatric speciation)
• Polyploidy:
Types of Speciation
• Allopatric– A physical barrier divides one population into two or
more populations. Over time each species evolves
and can no longer interbreed.
• Ex: grand canyon produced barrier that separated squirrels
• Sympatric– A new species evolves without a physical barrier.
• Ex: many insect species and plants (polyploidy is a mutation
where plants can no longer interbreed with the normal
population)
2. Convergent Evolution
• Unrelated species evolve similar traits even
though they are not closely related.
• These traits are often structurally very
different.
Examples
• Bird Wing
Bat Wing
Analogous Structures
• Result from Convergent Evolution
• Squid Eye
Human Eye
3. Coevolution
• The relationship between two species
might be so close that the evolution of one
species affects the evolution of the other
species.
• Mutualism
• Coevolutionary arms race
Orchid Fly
Garter snake consumes a poisonous newt
Label the following:
Do Now
• Explain the difference between divergent
and convergent evolution
Explain the differences
between:
– Homologous and analogous structures
– Convergent and divergent evolution
Tempo of Speciation
• Gradualism:
– Evolution proceeds in small, gradual steps
according to a theory called gradualism.
• Punctuated Equilibrium:
– Punctuated equilibrium explains rapid
spurts of genetic change causing species to
diverge quickly.
Chapter
15
Evolution
What do you think?
• What tempo of evolution does this model
represent?
– A. gradual
– B. elevated
– C. sequential
– D. punctuated
Do Now
• How did humans evolve?
Primate Evolution
16.2 Hominoids to Hominins
Hominins
 The lineage that most likely led to humans
split off from the other African apes
sometime between 8 and 5 mya.
 Hominins have bigger brains.
 Thinner and flatter face
 Smaller teeth
 High manual dexterity
 Bipedal
Human Evolution Ch. 16
• Primate adaptations
– high level of problem solving ability
– large brain size when compared to body
weight
– flexible shoulders
– flexible hand with an opposable thumb
African Origins
Human Evolution
Conclusion Activity
• Compare and Contrast Apes and Humans