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Introduction to Evolution
Chapter 15
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What
is the connection
between the words
EVOLUTION AND
REVOLUTION
What is Evolution ???
Evolution is “change over time”
It is the process by which modern
organisms have descended from ancient
organisms
What is a Theory
 A well
supported testable explanation
of a phenomena that have occurred in
the natural world
We are going to discuss and learn about
the Theory of Evolution
Charles Darwin
“Father of Evolution”
Set sail on the H.M.S
Beagle from England
all around the world,
especially the
Galapagos Islands
He made numerous
observations during
his travels
Darwin’s Observation’s
 DIVERSITY !!!!!!
 Living
organisms and Fossils
 Amongst the Galapagos Islands
Darwin noted that there were
difference in climate, vegetation, and
varieties in plant and animal types
Inferring in Groups

Make inferences about what particular
species of animals need to survive in the
Galapagos Islands
 ** Remember it’s not only their
PHYSICAL characteristics of any
organisms that make it survive but also its
behavior and relationship with its
environment
Darwin Presents His Case

On the Origin of Species

Darwin summarizes 6 main points
 #1 OVERPRODUCTION –most species produce
far more offspring than are needed to maintain the
population

#2 COMPETITION – since living space and food
are limited, offspring in each generation must
compete. Only a small fraction survive long
enough to reproduce
Main Points (continued)

#3 VARIATION - The characteristics of the
individuals in any species are NOT exactly
alike. They may differ in the exact size or
shape of a body, in strength, and in speed.
These differences are called VARIATIONS.
Others may affect the individual’s ability to
get food, to escape enemies, or to find a
mate.

#4 ADAPTATIONS –Because of variations, some
individuals will be better adapted to survive and
reproduce than others. In competition for
existence, the individuals that have favorable
adaptations to their environment will have a
greater chance of living long enough to reproduce.
An adaptation is any kind of inherited trait that
improves an organism’s chance of survival and
reproducing

#5 NATURAL SELECTION - “ Nature
selects the survivors”. Individuals with
variations that make them better adapted to
their environment survive and reproduce in
greater numbers than without such
adaptations.

#6 SPECIATION –Over many generations,
favorable adaptations gradually
accumulated changes become so great that
the net result is a new species.
Natural Variation VS Artificial
Selection

According to Darwin, natural selection is
the differences among individuals in a
species Naturally.
 In artificial selection, nature provided the
variation among different organisms , and
HUMANS selected those variations they
found useful.
The Struggle for Existence

Each member of a species must compete
regularly to obtain food, living space, and
other necessities for life.
 Those prey that are faster, better
camouflaged, or better protected can avoid
being caught.
Survival of the Fittest
FITNESS – is the
ability of an organism
to survive and
reproduce
 Individuals the are
better adapted or
MORE FIT are more
apt to survive

Evolution of Populations
Over
time, it is a
population that evolves
not an individual
organism
Descents with Modifications

Each living species has descended, with
changes, from other species over time
 According to the principle known as
common descent, all species-both living and
extinct were derived from a common
ancestor
Evidence of Evolution



Fossil records
Geographic distribution of
living species
Homologous Body
Structures- structures that
have different mature
forms but developed from
the same embryonic
development
Comparative Anatomy

Homologous structures have similar structures and
similar embryological development but have
different forms and functions ( example human
hand, whale flipper)
 Analogous structures have similar external forms
and functions but different internal structures
(example bird wing and insect wing)
Vestigial Structures

Structures that are remnants of structures
that were functional in an ancestral form

In the human, wisdom teeth, the coccyx,
and the appendix
Embryological Similarities

Many embryos look
very similar during the
early stages of
development