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Summary color is pink; vocabulary is
Hyperlinks are in green; they will
take to you videos and animations.
Unit 12 – Intro to Evolution
Background Image:
This katydid is well
adapted to look like
the leaves of its
habitat. In this unit
we will discuss
theories of evolution
and adaptation that
lead to such
phenomenon within
Background Image:
Due to the sensitive nature of this
unit I ask that we keep in mind
that the theories behind evolution
can often breed tensions because
of religious teachings.
These theories are part of
understanding the world of
science. Our scientific
discussions will focus on
attempting to explain natural
phenomena (or events).
Differing religious opinions are
okay, but religious based theories
on the history of life are not the
focus of this class.
Textbook Reference pg. 18
• Theory in everyday life is different
from the scientific theory – i.e.
someone has a theory on who will
win the Super Bowl.
• A scientific theory is an
explanation of natural and physical
phenomena that is supported by a
large body of scientific evidence
from multiple, independent
• Unlike hypotheses, theories are
well- established and highly
reliable – they are subject to
change as new information is
obtained or technologies
Textbook Reference pg. 10
• The Earth has millions of
kinds of organisms with an
amazing amount of
diversity, yet, we all share
similarities, the core of
which is DNA. (Every living
organism has it!)
• How are all these different
organisms related to each
• Evolution, or change in a
species over time, is the
process by which modern
organisms have descended
from ancient ones.
• For example, the ancient
horse a was about the size
of a medium dog!
Who is
Textbook Reference pg. 393-396
• The British scientist Charles
Darwin is credited the most
in our understanding of
evolution. After college in
1831, Darwin joined the crew
of the ship the H.M.S.
Beagle for a voyage around
the world (5 years!).
• During his travels, Darwin
took observations,
specimens, and collected
evidence for the variety of
species on this planet.
• He later proposed a
hypothesis about the way life
changes over time .
• That hypothesis, now
supported by a larger body
of modern evidence, became
the theory of evolution.
Darwin Cont.
• When the ship was anchored, he
collected plant and animal
• In one single day in the Brazilian
rainforest he collected 68 different
species of beetles!
• When sailing, Darwin took
observations of the organisms and
kept detailed notes.
Textbook Reference pg. 394ápagos /Galápagos .lg.jpg
• Probably his most influential location on Darwin’s journey was
the Galápagos Islands off the coast of South America; 500
miles west of Ecuador in the Pacific Ocean, directly on the
• Although they were very close together (50 to 60 miles and
still within eye sight), the islands had very different climates
and very different plants and animals living there.
• Darwin learned that each island had a different variety
of land tortoises.
• One island turtle has a long neck and curved opening
in the shell to allow for the organism to search for food
because of sparse vegetation (or plant life).
• Yet, another island with a lot of plant life has a turtle
that is very close to the ground the with a short neck
making it easier to eat.
Textbook Reference pg. 399-400
• In his travels, Darwin compared
living organisms to fossil
evidence that he collected
throughout his voyage.
• A fossil is the preserved
remains of an ancient organism.
• Some living organisms he
observed looked like preserved
fossils, while others were unlike
any creature he had ever seen!
(EX Dinosaurs)
• His evidence posed more
• Why had so many species
• How are ancient organisms
related to modern organisms?
On the Origin of Species
Textbook Reference pg. 396
The political cartoon (1861) is just
one example of the negative
reaction to the theories
explained within the book.
• Darwin used his notes and
scientific findings to build his
theory of evolution; it took him
years before he was willing to
publish his work because of
the drastic controversy it
would (and did) cause.
• His book, On the Origin of
Species [By Means of Natural
Selection] was published in
• In it he argued that life has
been evolving for millions of
• His book sold out in the first
day and became an instant
best seller!
Five Basic Concepts
of Natural Selection
• Use the chart to list the 5 themes from On the Origin of
1. Variation Among Species
Textbook Reference pg. 407,409
• All species have genetic
variation (we now know)
caused by differences in the
DNA and genes of an
organism (EX color of fur;
shape of teeth; blood type;
hormone levels).
• Darwin argued that variation
was normal and was
• Characteristics vary within a
species and this can affect
the survival of individuals.
2. Struggle for Existence
Textbook Reference [Competition] pg. 38-39
Organisms produce more offspring than can survive.
Some that survive do not produce offspring.
Organisms are forced to compete for resources.
This is called the struggle for existence; members of each
species must compete for the necessities of life (food,
water, & space).
• Survival affected by short-term natural disasters
– EX droughts, fires, floods, snowstorms, hurricanes, etc.
• And affected by long-term changes in the environment
– EX ice ages, biome shifts, etc
3. Adaptations
Textbook Reference pg. 9, 397-399
• Darwin began to realize that organisms have certain
characteristics or behaviors that allow them to survive in their
• An adaptation is an inherited characteristic (EX a longer neck)
that can increase an organism’s chance of survival.
• If they live long enough, they will reproduce and pass on their
Knowledge Check
Textbook Reference pg. 469
The diagram
below shows
features of the
varieties of finches
in the Galapagos.
How can the
diagram help us
understand the
evolutionary terms
like variation and
adaptation? Turn
and talk to your
4. Fitness
• Some organisms are
more suited to their
environment due to
natural variations in the
• Darwin used the term
fitness to define an
individual’s ability to
survive and reproduce.
• Individuals that are fit to
their environment survive
and leave more offspring
than those who aren’t.
5. Descent with Modification
Textbook Reference [Diagram] pg. 374-375
• Living species today are
descended (with modifications)
from common ancestral
species that lived in the past.
• Over time, traits [i.e. genes] for
less favored characteristics will
be eliminated from the gene
• Species today, therefore, look
different from their ancestors
because of historical changes.
Sketch, Darwin’s
Branching “Tree of Life”
Knowledge Check
The diagram below shows descent with modifications for
modern elephants. How can the diagram help us
understand evolutionary terminology like variation and
descent with modification? Turn and talk to your neighbor.
What is the gist of the
• Natural selection is the process by which individuals that
are better suited to their environment survive and
reproduce most successfully (AKA survival of the fittest).
• Organisms that are well adapted will be able to survive.
Over time, natural selection leads to changes in the
characteristics of a population.
• New species develop, increasing biodiversity.
• Video
• Video 2
Textbook Reference pg. 469
• Darwin understood variation can be a positive thing!
• He used the example that a dairy farmer would benefit
from breeding a cow that produces a lot of milk versus a
cow that does not.
• He coined the term artificial selection where nature
provided the variation and humans selected those
variations that are useful (EX a pure breed dog, the best
looking horse). Animation
Darwin’s Influences
• Many scientific theories and
observations in the years
before Darwin helped to
influence his theories on
• Some scientists long before
Darwin came to similar
• Most people at the time
thought Darwin’s opinions too
radical (or out there) to accept.
• The French scientist Jean-Baptiste Lamarck was one of the first
to recognize that life changes over time.
• He argued that certain traits present in an organism are always
passed on to offspring.
– EX giraffes stretched their necks to reach food.
– Their offspring and later generations inherited the resulting
long necks.
• Although some of his theories were flawed, the idea that species
change and adapt greatly influenced the theory of evolution.
• In 1795, the geologist James Hutton
published his hypothesis on the
Earth’s geology formed very slowly
over time, millions of years and are
shaped by natural forces (mainly the
• Most Europeans at the time believed
that the Earth was only a few
thousand years old, but Hutton
proposed that the Earth had to be
much older.
• If the Earth were millions of years
old, it would help to explain the
SLOW process of evolutionary
• Lyell’s book was published
just before Darwin set sail in
the Beagle.
• In his book, Lyell proposed
that scientists can observe
the processes that shaped
the Earth millions of year ago
in the present (volcanoes,
earthquakes, etc. all change
how the world looks).
• Darwin wondered if the Earth
can change over time, can
species change too?
Textbook Reference pg. 396,468
• A contemporary (same time
frame) of Darwin, Alfred Wallace
wrote an essay on evolution and
the process of natural selection
using his studies of plants and
animals a year before Darwin
published Origins.
• Darwin and Wallace both
presented their findings at the
same scientific conference.
• Darwin is remembered while
Wallace is often forgotten.
Textbook Reference pg. 115
• Extinction: the
destruction of a
• If an entire
population of a
species cannot
adapt, that species
becomes extinct.
• 99% of all species
that have ever lived
are now extinct!
• Humans contribute to
the extinction of many
plants and animals
because of pollution,
loss of habitat, and
Indian tigers, for
example, are a group of
tiger species that had
an original range from
India along Asia's
Pacific rim to northern
China as well as other
sections of Central Asia.
Their range today
outside of protected
areas has been severely
"Fragmented Habitat." Science Online. Facts On File, Inc. Web. 30 Jan. 2013.
• Many scientists say that the earth is currently experiencing
a mass extinction crisis.
• It is estimated that 1/5 or more of the world’s species will
become extinct if the rainforests alone are destroyed.
Mass Extinction
Textbook Reference pg. 378
Photo courtesy of Donald E. Davis,
also in public domain from NASA.
• There have been at least 5
mass extinctions during
Earth’s history, when a huge
% of the living species were
• At least one of these has been
attributed to meteor impact
and it’s consequences.
• Animation
Analyzing the Graphic
Chicxulub Crater, Mexico's
Yucatan Peninsula
180 kilometre (112 mi)
Most scientists now agree that
this event 65 million years ago
that marked the sudden
extinction of the dinosaurs as
well as the majority of life then
on Earth.
• Evolutionary theory is
constantly changing due
to new information that is
• EX The AIDS virus is
changing constantly, and
the flu vaccine must be
modified each year due
to changes.
• Species change, evolve,
over time, and that time
is now.