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EVOLUTION
Origins of life
-Earth formed about 4.6 billion years ago
-Early Earth had many active volcanoes.
-These volcanoes released:
1. water vapor, which eventually led to formation of
oceans
2. Gases, such as: methane, hydrogen, nitrogen,
ammonia, carbon dioxide, and
carbon monoxide
-Earth’s early atmosphere had little to no oxygen.
Miller-Urey Experiments
◦ Showed that organic
molelcules, specifically,
polypeptides (which are
chains of amino acids) could
be formed from elements
present on Early Earth
◦ These organic molecules of
polypeptides could join
together to create life
What were the first living organisms
on Earth?
◦ Fossil records show that the first living organisms appeared about
3.5 billion years ago and were simple, single-celled organisms.
◦ The sequence of development is as follows:
Anaerobic prokaryotes  photosynthetic prokaryotes 
unicellular eukaryotes  multicellular eukaryotes
*anaerobic means no oxygen is required
Where did oxygen first come from?
◦ Most likely from photosynthetic bacteria, such as cyanobacteria
Anaerobic prokaryotes  photosynthetic prokaryotes  unicellular
eukaryotes  multicellular eukaryotes
Where did oxygen first come from?
◦ Most likely from photosynthetic bacteria, such as cyanobacteria
Anaerobic prokaryotes  photosynthetic prokaryotes  unicellular
eukaryotes  multicellular eukaryotes
Review: What is the formula for photosynthesis?
Evolution
Question to think about: Do humans ‘come from’
monkeys?
By the end of this Evolution unit, you will be able to
answer this question correctly as a scientist!
Evolution
Definition: a change in
the genetic
composition of a
population of
organisms over time.
Summary: change in
organisms over time.
Evolution
You may also see this definition:
Descent with modification from common
ancestors
How does evolution occur?
◦ First hypothesis, which was incorrect
(i.e. unsupported, was proposed by
Jean-Baptiste Lamarck in 1809
◦ Theory of acquired traits: physiological
changes that an organisms acquires
throughout its lifetime may be passed
onto offspring
◦ This idea was good in that it was a
hypothesis on how evolution occurred,
but it was bad in that there is no
evidence to support it.
Theory of acquired traits: not a
supported hypothesis for evolution
Hypothesis:
Actual results
Darwin’s Theory of Natural Selection
◦ English naturalist
◦ Sailed on the HMS Beagle in
1831to make natural history
collections
◦ His observations led to the
theory of evolution by
natural selection
◦ Wrote a book titled, On the
Origin of Species
Review: define evolution
a. an adaptation of an organism to its environment
b. a sudden replacement of one community by
another
c. a geographic or reproductive isolation of
organisms
d. a process of change in organisms over a period of
time
Review: define evolution
a. an adaptation of an organism to its environment
b. a sudden replacement of one community by
another
c. a geographic or reproductive isolation of
organisms
d. a process of change in organisms over a period of
time
Review: Which statement would most likely be in
agreement with Lamarck’s theory of evolution?
a. Black moths have evolved in an area because they were better
adapted to the environment and had high rates of survival
and reproduction.
b. Geographic barriers may lead to reproductive isolation and the
production of new species.
c. Giraffes have long necks because their ancestors stretched their
necks reaching for food, and this trait was passed on to their
offspring.
d. Most variations in animals and plants are due to random
chromosomal and gene mutation.
Review: Which statement would most likely be in
agreement with Lamarck’s theory of evolution?
a. Black moths have evolved in an area because they were better
adapted to the environment and had high rates of survival
and reproduction.
b. Geographic barriers may lead to reproductive isolation and the
production of new species.
c. Giraffes have long necks because their ancestors stretched their
necks reaching for food, and this trait was passed on to their
offspring.
d. Most variations in animals and plants are due to random
chromosomal and gene mutation.
Evolution by natural selection
Definition: a primary mechanism of evolution in which organisms
with favorable traits are more likely to reproduce
Summary: main process for evolution to occur
Components of natural selection
1. There are not enough resources
(such as food) for all individuals in a
population
2. There is variation of traits among
individuals
3. These traits are heritable
4. Individuals with the ‘better’ trait will
survive longer and reproduce more
than those without the ‘better’ trait.
Important vocabulary words
Fitness: an organism’s relative ability to
survive and produce fertile offspring.
Adaptation: feature that improves
fitness. Example: camouflage
Guided Practice: beetles
1. There are lots of beetles, more than the
environment can support
2. The beetles vary in color. Some are
green, and some are orange.
3. The colors are inherited from parents.
4. Birds like to eat green beetles. So,
being an orange color is a better trait
because they are not eaten. Orange
beetles are better at surviving and
reproducing (have higher fitness)
Being orange is an adaptation!
Guided Practice: beetles
1. Did evolution occur? Why or why not?
2. How did evolution occur?
Guided Practice: beetles
1. Did evolution occur? Why or why not?
Yes, because there was change in the
population over time. The beetles were
both green and orange in the beginning,
but at the end, all beetles are orange.
2. How did evolution occur?
Through natural selection. The orange
beetles were better at surviving and
reproducing.
Explain how giraffes evolved to have
longer necks: Think-pair-share 5
minutes
Things to think about in your answer:
1. Should there be more or fewer individuals in a
population than an environment can support?
What resources do giraffes need to survive?
2. Is there variation in neck length amongst the
giraffes in the population, or are they all the
same?
3. Is neck length heritable or is determined by the
environment?
4. Are certain giraffes better at surviving and
reproducing than others? Why or why not?
Other mechanisms of evolution
1. Natural selection
2. Mutations
3. Genetic drift
4. Gene Flow
5. Nonrandom mating
Mutation
Change in genetic information
Mutations that occur in gametes (sperm and
eggs) are passed onto offspring
May contribute to genetic variation
Genetic Drift
When genetic composition changes by chance
More noticeable in smaller populations
Gene flow
Immigration or emigration of individuals
Nonrandom mating
Selective mating based
on preferences
Phylogenetic trees
Hypotheses for the
evolutionary relatedness
of organisms
Cladograms
◦Diagrams used to
show how organisms
are related by
descent from
common ancestors
How to read a cladogram
◦ Organisms that are closer to
each other share a more
recent common ancestor
◦ Example: a chimp is more
closely related to a mouse
than a pigeon because the
chimp & mouse share a more
recent common ancestor
How to read a cladogram practice:
◦Is the lizard more
closely related to a
salamander or a
hagfish?
Evidences for evolution
1.Molecular
2.Anatomy
3.Vestigial structures
4.Comparative embryology
5.Fossils
Evidences for Evolution: Molecular
1. All organisms have the same 20 amino acids that make up proteins
2. All organisms use ATP
3. Organisms that share similar traits also show similar DNA base sequences
-Comparing DNA sequences is one of the best ways to understand
evolutionary relationships
Evidences for Evolution: Anatomy
◦ Homologous structures:
structures among
organisms that are similar
structurally, but different in
function.
◦ Due to inheritance from a
recent common ancestor
Evidences for Evolution: Anatomy
◦ Analagous structures:
structures among organisms
that are different
structurally, but appear and
function similarly.
◦ These occur when the
organisms live similar life
styles, not because of
sharing a recent common
ancestor
Evidences for Evolution: Vestigial
structures
◦ Structures that lost most or all of their ancestral function,
but have been retained through evolution.
◦ Examples:
Vestigial Structures Example:
◦ Pelvic bones in whales
◦ Whales don’t walk. So, why do they need
pelvic bones?!?!?!
Answer: These pelvic bones have been reduced
and are not used. This vestigial structure
suggests inheritance from a recent common ancestor
Vestigial Structures Example:
◦ Pelvic bones in whales
◦ Whales don’t walk. So, why do they need
pelvic bones?!?!?!
Answer: These pelvic bones have been reduced
and are not used. This vestigial structure
suggests inheritance from a recent common ancestor
Did you know that: whales are mammals??
Vestigial structure example:
Human embryos have tails, which later
moves into the body, but retains much
of its bone structure in the coccyx
Evidences for Evolution:
Comparative Embryology
◦ Embryos of animals with
backbones (vertebrates)
look very similar
◦ This indicates that the
rules of embryonic
development are similar
among vertebrates,
meaning that all
vertebrates share a
common ancestor
Evidence for Evolution: Fossils
-Fossils are preserved remains of
animals, plants, and other
organisms.
-When fossils are arranged
according to age, a progressive
series of changes (i.e. evolution)
can be observed
Stop and jot: 4 minutes
In your notes, list and explain four evidences of evolution.
Speciation
◦ Speciation is a process by which species evolve
◦ A species is a group of organisms that can interbreed and
produce fertile offspring
◦ How do species form?
1. Geographic isolation
2. Behavioral isolation
Geographic isolation
◦ Populations separated
by geographic barriers
(rivers, mountains,
bodies of water, etc.)
◦ Doesn’t always lead to
new species.
Behavioral isolation
• Capable of
interbreeding, but
have different
courtship
rituals.
Patterns of evolution
1.Adaptive radiation
2.Convergent evolution
3.Coevolution
Patterns of Evolution
Adaptive
Radiation
◦ Small group of
species evolve into
different forms
that live in
different ways.
Patterns of Evolution
Convergent Evolution
◦ Unrelated organisms begin to resemble each
other.
◦ Similar environmental demands. Produces
analagous structures
Patterns of Evolution
Coevolution
◦ Two species
evolve in
response to
changes in each
other.
Evolution over a larger time scale
1. Punctuated equilibrium:
periods of quick evolution
followed by periods of
stasis.
2. Gradualism: evolution
that occurs gradually, or
slowly over time.
Evolution
Question to think about: Do humans ‘come from’
monkeys?
By the end of this Evolution unit, you will be able to
answer this question correctly as a scientist!
Answer:
◦ No, humans do not ‘come from’
monkeys.
◦ Humans and apes (chimpanzees &
gorillas) do share genetic similarities,
and thus, we share a recent common
ancestor!
◦ Examples: large brains relative to
body size, relatively long childhood,
intelligence (reasoning, sense of self),
and more.
Classification
https://www.youtube.com/watch?v=F38BmgPcZ_I
Crash course video & worksheet