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10.1 KEY CONCEPT
There were theories of biological and
geologic change before Darwin.
What are some reasons why this creature would
have the specific traits it has; tentacles on its
mouth and long claw like nails?
Early scientists proposed ideas about
evolution.
Evolution is the biological change process by
which descendants come to differ from their
ancestors.
 A species is a group of organisms that can
reproduce and have fertile offspring.

Discussion Questions:
1.
What are some examples of species?
2.
Would a donkey and a horse be considered the same species?
Scientist
Contribution
Linnaeus (1700s)
Classification System; hybridization
Buffon (1700s)
Species shared ancestors; earth is older
E. Darwin (1750s)
Common ancestor
Lamarck (1809)
Inheritance of acquired characteristics
Cuvier (early 1700s)
Catastrophism
Hutton (late 1700s)
Gradualism
Lyell (1830s)
Uniformitarianism
10.2 KEY CONCEPT
Darwin’s voyage provided insight on
evolution.
Darwin observed differences among
island species.

Variation is a difference in a physical trait.
 Examples: Tortoises and Finches in the Galapagos
Islands
 What variation do you see in the tortoises below?

An adaptations is a feature that allow an
organism to better survive in its environment.
– Species are able to adapt to their
environment.
– Adaptations can lead to genetic
change in a population. HOW??
Variation v. Adaptation


For each trait, give a
variation and then
explain how it could
become an
adaptation.
Example: Neck rotation in
owls
 Variation: amount of
rotation, some small,
medium, large, etc
 Adaptation – Owls with
larger amount of rotation
can seen more to get
food and survive

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Neck length in giraffes
Size of dolphins
Sense of smell in dogs
Muscle amount in
Huskies
Amount of blubber on
penguins
Darwin’s Evidence
• Fossils
• Earthquake
Adaptation Scenario
Imagine that you are a scientist, studying sea
lions on the Galapagos Islands. The sea
lions lose their main food source when
anchovies are kept away from the island.
The only other food available is a small
species of crab that lives on the seafloor 100
feet below. What kind of traits would the sea
lions adapt and how would they help?
 Discuss as a group and write your response

10.3 Several key insights led to
Darwin’s idea for natural selection.



Darwin noticed a lot of variation in domesticated plants
and animals.
Artificial selection is the process by which humans
select traits through breeding.
What are some examples of humans using this
process?
neck feathers
crop
tail feathers

Natural selection is a mechanism by which
individuals that have inherited beneficial
adaptations produce more offspring on average
than do other individuals.
 Heritability - ability of a trait to be passed down.
 Overpopulation and limited resources cause struggle
for survival
 So how long does natural selection take?
○ Darwin proposed that adaptations arose over many
generations.
Natural selection explains how evolution can occur.
• There are four main principles to the theory of natural
selection.
– Variation: heritable differences that exist in every
population
– overproduction: too many offspring compete for
resources
– adaptation: certain variation allows individuals to survive
better than others
– descent with modification: more individuals have an
adapted trait with each generation
VARIATION
Natural selection acts on EXISTING variation.
• Fitness is the measure of survival ability
and ability to produce more offspring.
• Natural selection can act only on traits
that already exist.
• Structures take on new functions in
addition to their original function.
five digits
wrist bone
Natural Selection Example

Jaguar Example:
 Overproduction – not enough food for all offspring to
survive
 Variation – teeth and jaw size, some are born with
slightly larger than others
 Adaptation – larger teeth and jaws allow jaguars to eat
more things; survive more than those who don’t have
this trait
 Descent with modification – because larger teeth and
jaws are beneficial to survival, they will be passed on
more often and become more common in the population
With the person sitting next to you:
Look at the example of the Jaguar on page
307 in the books
 Choose your own animal and explain how
that animal could fit all 4 principles of natural
selection in the same way as the example.
 Create an environmental change that would
cause natural selection in the organism you
chose. Write it down and turn in.

10.4 KEY CONCEPT
Evidence of common ancestry among species comes
from many sources.
Several Sources of Evidence

Fossils
 Fossils in older layers are more primitive
than those in the upper layers.

Geography
– island species most closely resemble nearest
mainland species
– populations can vary from one island to another

Embryology
– identical larvae, different adult body forms
– similar embryos, diverse organisms
Larva
Adult crab
Adult barnacle

Anatomy
– Homologous structures are similar in structure but
different in function.
– Common Ancestor

Anatomy
 Analogous structures have a similar function.
 Common environment, not common ancestor
Fly wing
Bat wing
Structural patterns are clues to the
history of a species.
• Vestigial structures are remnants of organs or structures
that had a function in an early ancestor.
• Ostrich wings
• Other examples?
10.5 KEY CONCEPT
New technology is furthering our understanding of
evolution.
Fossils provide a record of evolution.

Paleontology is the study of fossils or extinct
organisms.

Paleontology provides evidence to support
evolution.
Molecular and genetic evidence support fossil and
anatomical evidence.

Hox genes indicate a very distant common
ancestor.
– control the development of specific structures
– found in many organisms
Evolution unites all fields of biology.
• Scientist from any fields contribute to the understanding
of evolution.
• The basic principles of evolution are used in many
scientific fields.
Evidence for Evolution –
Opinion Statement

Do you believe the evidence we
discussed is enough to justify belief in
evolution? Why or why not?
Homework
1.
2.
3.
4.
Create a Venn Diagram Comparing and
Contrasting Analogous, Homologous, and
Vestigial Structures
Do the VOCABULARY CONNECTIONS
(#1-5) on page 323 in your book
Due Tomorrow
Quiz Friday on Ch. 10!!