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Unit Learning Goals
a. Trace the history of the theory.
b. Explain the history of life in terms of
biodiversity, ancestry, and the rates of
evolution.
d. Relate
natural
selection to
changes in
organisms.
Cosmos:
Some things
that
Molecules do
Where do I live?
• What type of
environment am I best
“fit” for?
• Hot/cold????
• Wet/dry???
• Why
• Organisms have traits
(GENES) that help them
to survive in different
environments.
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A variation is a small change in a trait that makes an
individual slightly different from other members of its
species.
• All organisms in a
population are not the
same.
Variation/diversity exist.
• What causes this
variation??
What is Fitness?
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• Fitness is a measure of
reproductive success.
(survive long enough to
reproduce)
• Reproductive success:
Having traits so that an
organism is able to pass on
genes onto the next
generation (and in a way so
that the next generation can
also pass those genes on)
• Any trait that promotes
survival — at least until one's
reproductive years are over
increases fitness.
• Such traits are called
adaptations.
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What if an organism has a trait.
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that makes it impossible to live in its
environment?
• The organism will not
survive.
• If it does not survive—
it CANNOT reproduce.
• If it does not
reproduce—its genes
are not passed to the
next generation.
What if the environment changes? 7
• If they do not have the traits (genes)
that enable them to survive…they die,
and DO NOT reproduce.
• If they do have the traits, then they
survive…and reproduce.
• SO… the next generation has more of the “fit” traits
for THAT environment.
• The population then CHANGES!
• This is a very slow process….does not occur over
night…many generations must past before any change
in the population can be seen.
Natural Selection
Current Theory …
Natural Selection
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•Also know as “survival of the fittest.”
•Only certain members of the population
will survive and reproduce.
•Ones that survive are most suited to the
environment—they are the most fit!!.
survival of the fittest
Humans have been doing this for 1000s of years!
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Dog Breeds
Corn
Pigs
Humans select and breed for certain traits.
Examples: The largest hog, the cow that gives the
most milk, fastest horse, or cutest dog.
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Where do NEW
traits come
from?
How do new traits arise?
a) Mutations.
b) Sexual Reproduction.
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• Mixing of genes makes new
combinations
• A combo of traits may be necessary
for survival……so… sexual
reproduction and crossing over can
create new combination of traits.
Decent with modifications
These changes increase
a species’ fitness in their
environment.
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THE BASICS: A review
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• ADAPTATIONS (traits) that are
favorable become more prevalent
within that population.
• These traits will be passed on to the
next generation.
• The GENE POOL of a population
CHANGES in favor of the “FITTEST”
phenotype & genotype!!!
Environment selecting “good” traits for THAT environment.
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Example: Peppered Moth
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Sampling the birds that died as well
as those that survived showed that
•the larger birds were favored
over the smaller ones
•those with larger beaks were
favored over those with smaller ones.
Beak length
(mm)
Beak depth
(mm)
Dead birds
10.68
9.42
Survivors
11.07
9.96
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of Small beaks
From 1976 through 1977, a severe drought struck an island in the Galapagos.
Some phenotypes are more fit than others when it comes to
competing for resources. The more “FIT” phenotype will survive
and have the possibility of passing its alleles to the next
generation.
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Review Clip
History
• James Hutton -1785-Proposed that
the Earth is millions of years old.
• Many land formations took millions
of years to form.
• Known as the founder of modern
geology.
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History
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• Thomas Malthus -1798• Proposed that populations outgrew
their
food supplies, causing
competition
between organisms and a struggle for one
species to survive against another
• This "struggle for existence" drives population
change.
History
Jean-Baptiste Lamark
-1809• Believed that all life
forms evolved and that
the driving force of
evolution was the
inheritance of acquired
characteristics.
• He believed that
organisms changed due
to the demands of their
environment.
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What we
understand
now:
•Charles Lyell -1830-proposed
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that plant and animal species had
arisen, developed variations, and
then became extinct over time.
•He believed that every animal or
plant, including humankind, was
the present is the key to
adapted to the niche in which it was understanding the past
created.
•He also believed that
the Earth’s physical
landscape changed over
a long period of time.
15.1
• Alfred Russel Wallace -1858
• Emphasis was based on the idea
of competition for resources as
the main force in natural
selection.
Best known for independently
proposing a theory of natural
selection which prompted Charles
Darwin to publish on his own theory
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• Charles Darwin -1859-
Publishes “On the Origin of
Species”
• Believed that Natural Selection
is the driving force for evolution.
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Charles Darwin
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Summary of Darwin’s Ideas
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1. Individual organisms differ, and
some of this variation is heritable.
2. Organisms produce more offspring than can
survive, and many that do survive do not
reproduce.
3. Because more organisms are produced than
can survive, they compete for limited
resources.
4. Individuals best suited to their environment
survive and reproduce most successfully.
Summary of Darwin’s Ideas
5. These organisms pass their heritable
traits to their offspring. Other
individuals die or leave fewer offspring.
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6. This process of natural selection causes
species to change over time.
7. Species alive today are descended with
modification from ancestral species that lived
in the distant past.
8. This process, by which diverse species evolved
from common ancestors, unites all organisms on
Earth into a single tree of life.
Review Clip
Review Clip: 10min
Whale Video Clip- Intro to
evidence ( Questions in packet)
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Evidence for Change Over Time
Fossil Record
• Fossils that show
how the same
organism looked
millions of years
ago.
• Paleontology
• Use rock layers
• 1) Isotope dating
Clip
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Fossil Record
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2) Relative Dating
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Homologous structures
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Homologous structures
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Analogous versus Homologous Structures
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Vestigial organs
• Organs or
structures that
do not seem to
be used by the
organism any
longer.
• They are
usually reduced
in size.
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Vestigial Organs
c
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•Things
that cause
change.
•Why we
are all a
little bit
different
…
Genetic Comparison
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• The numbers represent
the number of amino
acid differences
between the beta chain
of humans and the
hemoglobins of the
other species.
• In general, the number
is inversely proportional
to the closeness of
kinship.
GEOGRAPHIC DISTRIBUTION
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• Organisms that are related change/adapt according
to their environment.
Adaptive Radiation
• The evolution of many
diversely adapted species from
a common ancestor
• Relatively rapid
• Usually occurs when a population
colonizes an area of diverse
geographic or ecological conditions.
• New niches
•Each species
becomes
specialized for a
different set of
conditions
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