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Evolution
Chapter 16
Misconception
Evolution is “just a theory”
Scientific theories are explanations that are based
on supporting evidence, valid predictions, and
have been tested over and over! The “everyday”
definition of a theory can be confusing!
Like the Cell Theory (another scientific theory), it
can be changed, modified or disproved if scientific
evidence supports that action!
Scientific Theory
 Well-tested explanation that makes
sense of a great variety of
scientific observations
 Examples:
– Theory of Evolution.
– Cell Theory
Objectives
 Describe what evolution explains.
 Identify key observations from Darwin's
voyage that led to his theory of Natural
Selection.
 Summarize ideas from other Scientists that
influenced Darwin’s work.
 Describe the two main points of Darwin's
theory of Evolution.
Previous Ideas about
Organisms/Earth (that were wrong)
 Life, Species, & Earth is
unchanging!
 Earth itself is less than 10,000
years old
What is Evolution?
Evolution = The process of
changing/transforming life over time.
 Explains:
–how species have changed.
–how new species replace extinct
ones.
 Claims that all organisms originated
from a common ancestor.
What is Evolution? - YouTube
Isn't Evolution Just a Theory? - YouTube
What do you think you will be
doing when you are 22???
•
•
•
•
22 yr old scientist
Set sail for 5 yrs on the HMS Beagle
Studied Nature on Galapagos Islands
Darwin collected a lot of data:
• Plant & animal specimens (birds,
bugs, etc.)
• Took meticulous notes about what he
observed
1. Organisms varied around the world
2. Organisms vary locally
1. The Tortoises on each island of the
Galapagos had a different type of shell
2. The Finches on each island of the
Galapagos had differently (uniquely)
shaped beaks
3. Organisms vary over time (fossil evidence)
1. Example – Glyptodonts
Scientists that Influenced Charles Darwin
Georges Buffon (French Naturalist,
1750)
– Earth is much older than we thought!
– Found that fossils are similar to living
species!
Charles Lyell (Geologist)
• Said Earth changes through
geological processes such as:
• Canyon / River
• Mountain /Earthquake
Thomas Malthus (1838)
 Stated that populations grow faster than the
environment can support them.
 Therefore, it is almost impossible for all
offspring survive!
 Leads to a “struggle for existence”
Alfred Wallace (British Naturalist, 1858)
•Came up with the same conclusions as
Darwin!! But didn’t get credit 
Lamarck (French Naturalist, 1800)
– Stated that life changes over time (he
was correct)
– Came up with the wrong mechanism for
evolution
 Life changes/evolves by adaptations (correct)
 Inheritance of Acquired Characteristics
(wrong)
Adaptation (def.) – inherited characteristic that
improves an organism's ability to survive and
reproduce in a particular environment
EXAMPLES??
Lamarck’s Mistake
 Came up with WRONG mechanism
for evolution (acquired
characteristics)
 Did not account for genetics!
 Acquired characteristics is NOT
how a species changes over time!
Adaptations
Before we can understand Darwin’s Theory of Evolution through NATURAL
SELECTION…we must first understand adaptations.
Explain what features these organisms have and how it helps them…
Darwin’s Two Main Points in his book:
On the Origin of Species
1. Descent with modification
Process by which descendants of organisms
spread into various habitats and accumulate
adaptations to diverse ways of life
 Example: Snowshoe Hare and Jackrabbit

Darwin’s Two Main Points in his book:
On the Origin of Species
2. Natural Selection is
the mechanism for
evolution

Process by which
individuals with
inherited characteristics
well-suited to the
environment leave more
offspring than others
What is Natural Selection? - YouTube
Natural Selection
Misconception
Evolution involves organisms “trying” to adapt
and Natural Selection gives organisms what they
need to survive.
There is no “trying” involved
in evolution!!! Organisms have
no control over their traits or
adaptations.
Natural selection does not have
intentions, and can not sense
what organisms need to survive.
It does not “grant” adaptations.
Natural Selection
1.In nature, populations (of organisms)
contain many individuals with variations
(genetic mutations) which make them
slightly different from each other.
2.All those individuals deal with the
struggle for existance (getting enough food,
water, shelter, etc.) to stay alive.
3.Survival of the Fittest – individuals with
the helpful adaptations will live longer than
others and be able to reproduce.
4.Those beneficial adaptations will be
passed on to offspring & future generations!
Evolution: How does Evolution
Actually Work? (Natural Selection!)

Evolution: Videos for Students: Evolving Ideas
Do you REALLY understand Natural Selection???
You will write a paragraph
explaining why giraffes have
long necks today….Using
Darwin’s theory of natural
selection correctly!! Use the
diagram to help you if
necessary!
Evolution
Evolution Has Left Much Evidence
Fossil Evidence


Fossil – any preserved remains left by organisms that
lived in the past
As ground “strata” go deeper, older fossils are found.
This shows how life’s organisms change in form over
time.
Homologous Structures
(Def.) Similar structure found in more than
one species that share a common ancestor
Vestigial Structures

(Def.) Remnant of a structure that may have had an
important function in a species' ancestors, but has
no clear function in the modern species.

Shows that species with these structures must have
all come from a common ancestor and simply
changed over time!

“Remodeling Process”

Example: Hind legs on Whales

Evolution Primer #3: How Do We Know
Evolution Happens? - YouTube
Similarities in Development

Embryos of related species
have similar stages of embryo
development

Ex. Throat pouches

Supports that all vertebrates
evolved from a common
ancestor.
Molecular Biology

Organisms that are more closely related have more
similar DNA base pair sequences.

Supports idea that similar sequences (genes) are
come from a common ancestor.
Geographic Distribution

Certain species evolved from ancestors that lived in
a specific place, which is why related species are
found mainly in those specific regions today!

Ex. Australia & Marsupials