EVOLUTION
WHAT WILL WE COVER IN THIS CHAPTER?
Observing organisms allows us to see unity and
diversity.
 The arrangement of rock layers can tell us the relative
age of the layers and any fossils found in them.
 Radioactive isotopes help date rocks on an absolute
scale.
 Strategies for survival affect the population of all
organisms.
 Darwin describes the mechanism of evolution-natural
selection.
 The events of evolution have occurred over vast time
periods, mostly before the present.
 Evidence for elephant evolution can be pieced together
to explain modern day elephants.

THE GRAND CANYON
Clocks in Rocks - Keywords

Parent element


The original unstable element
Daughter element

The new more stable element
Clocks in Rocks - Keywords

Isotopes are atoms
of an element that
vary in the number of
neutrons they have.
This can make them
unstable.

Radioactive
decay occurs when
unstable atoms (like
radioactive isotopes)
break down to form
more stable isotopes.
Clocks in Rocks - Keywords
Half-life is a
measurement of
how long it takes
for radioactive
decay to occur. It
can be used to
more accurately
date how old
fossils and rocks
are.
Clocks in Rocks - Keywords


Radiometric
dating is a process
used by scientists to
measure the amount
of various isotopes
in rocks.
Radiometric dating
provides evidence
that fossils and rock
layers have different
ages.
EXPLORE ACTIVITY (WHO WILL SURVIVE?)
 Variations
(differences
within a species) between
individuals of a species
determines which ones
survive to reproduce.
 Since individuals with the
most successful
characteristics survive,
the population will
eventually change over
time.
HISTORY OF EVOLUTIONARY THEORY:
Evolutionary theory has changed over
time. There have been three main
ideas:
1.
2.
3.
Spontaneous Generation
Inheritance of Acquired
Characteristics
Natural Selection
SPONTANEOUS GENERATION:
 The
idea that organisms could come from
absolute nothingness. They would spring
into existence fully formed and perfectly
suited to their environment.
ACQUIRED CHARACTERISTICS
Any
characteristic the parent
obtains will be passed on to
their offspring.
ACQUIRED CHARACTERISTICS:
Disproved
by mice
experiment:
PARENTS
OFFSPRING
Mice with tails
removed have
babies with tails!
Mice with tails!
NATURAL SELECTION (DARWIN):
Species that have the best variations will be
better adapted to their environment.
 They will be more likely to survive.
 They will reproduce and pass their genes on to
the next generation.
 Over time, the entire species should change as a
result.
 Four parts to natural selection:

1.
2.
3.
4.
Variation
Adaptation
Selection
Genetic change over time
NATURAL SELECTION:
 Variation:
There are genetic differences
between individual members of a species.
PEPPER
MOTHS:
DARK AND
LIGHT
http://taggart.glg.msu.edu/isb200/BISTOND.JPG
NATURAL SELECTION:
Adaptation:
Any trait,
characteristic, or behavior that
helps an organism to survive to
reproduce.
http://tidepool.st.usm.edu/pix/peppermoths.gif
NATURAL SELECTION:
Selection:
Some organisms survive,
others do not!
NATURAL SELECTION:
 Genetic
Change: The organisms
that survive pass on their genes!
ORGANISMS BECOME BETTER ADAPTED:
http://www.eryptick.net/oz2001/chick-camouflage-011030.jpg
ORGANISMS BECOME BETTER ADAPTED:
Organisms become better adapted:
http://brgov.com/dept/animal/Images/common-walking-stick.gif
IMPORTANT THINGS TO REMEMBER:
 Individuals

Populations of species evolve
 Organisms

do not evolve
do NOT acquire characteristics.
They occur naturally (GENES) among individuals of
a population
 Evidence
of evolutionary
relationships is based on the
following things:
Anatomical Evidence
a. Homologous Structures: body structures
organisms share in common even if
they are used for different functions.
1.

Human hand and whale fin
1. Anatomical Evidence
b. Vestigial Structures: structures that are
inherited, but are reduced in size and are
often unused.
 Reasoning- an organism may have evolved so
that the function of a certain structure is no
longer valuable.
 Example: Pythons have hip and leg bones.
Example: Humans have miniature tailbones;
some have muscles in their ears that are
vestigial; also, humans have an appendix that
does not seem to serve a function.
2. Embryological likeness: similarity in
development of the babies
3. Fossil record:
looking at the
similarities between
fossil bones of
organisms to
determine how
related they are
http://entomology.unl.edu/lgh/insectid/images/insectevolution.jpg
4. Biochemical
likeness: studying
the protein
similarities
between
organisms. The
greater the
similarity, the
closer the
relationship.
http://www.woodrow.org/teachers/bi/1995/clado-restr-map.gif
5. DNA analysis: studying the similarities in the
nitrogenous base sequences in DNA, the
closer the match, the closer the relationship
Chromosomes of a human (left)
and a chimpanzee (right)
98.5% identical!!
EXPLAIN: LEARNING ABOUT LIFE
Darwin travelled on
the Beagle around the
world and began to
explain the great
diversity of life.
 Darwin noticed plants
and animals had
adaptations.
 Adaptations are
characteristics that
help an organism
survive.
