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Chapter 6: Evolution
Charles Darwin
Georgia Performance
Standards
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S7CS8 Students will investigate the
characteristics of scientific knowledge
and how it is achieved.
What is Science?
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Science is a way of learning about the
natural world…
Science skills –
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Observing
Inferring
Predicting
Classifying
Making models to learn more
Scientific
Inquiry/Method
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Steps
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Posing questions
Developing a hypothesis
Designing an experiment
Collecting and interpreting data
Drawing conclusions
Communicating
Experiments must be
repeatable!
Georgia Performance
Standards
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S7L3 Students will recognize how
biological traits are passed on to
successive generations.
c. Recognize that selective breeding
can produce plants or animals with
desired traits
This is the study of
Genetics…
Georgia Performance
Standards
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S7L4 Students will examine the
dependence of organisms on one
another and their environments.
c. Recognize that changes in
environmental conditions can affect
the survival of both individuals and
entire species.
People have always had
an impact…
Weather/Climate
Endangered Species
Extinct Animals
Georgia Performance
Standards
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S7L5 Students will examine the
evolution of living organisms through
inherited characteristics that promote
the survival of successive generations
of their offspring.
Most people know nothing
about evolution. It is important
to know the basic components
of the theory.
What is Evolution?
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Textbook definition:
Evolution
The gradual change in a species over
time.
What is a Species?
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Textbook definition
Species- A group of organisms
that are physically similar and
can mate with each other and
produce offspring that can also
mate and reproduce.
What is a variation?
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Textbook definition
Variation
Any difference between individuals of
the same species.
What is Natural
Selection?
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Textbook definition
Natural Selection
A process by which individuals that
are better adapted to their
environments are more likely to
survive and reproduce than others of
the same species.
Before Darwin…
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Many scientists believed in the fixation of
species – this theory held that all the current
animals were the exact same as the first
animals…
The problem with this theory was change
could be observed and even caused…as in
selective breeding.
Selective breeding is artificial selection.
Charles Darwin
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British Naturalist that helped shape
the theories of evolution.
Darwin developed the idea of Natural
Selection:
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Organisms with the best traits are more
likely to survive and reproduce.
These traits will get passed down from
parents to offspring.
Darwin’s Finches
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Darwin observed 13 species of
finches on the Galapagos Islands.
He noticed they all looked very
similar, except for slight
differences in body size, beak
shape and eating habits.
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These are
examples
of the
finches
Darwin
observed
during his
time on the
island.
Darwin’s Finches (Cont)
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Darwin also noticed these finches
looked similar to finches along the
South American coast.
He hypothesized the 13 Galapagos
finches evolved (changed over
time) from the South American
species.
Competition and Survival
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These different groups of birds had to
compete for food.
Finches with certain beak shapes, were
better able to eat certain foods- These
birds survived and reproduced.
After many generations, the different
groups of finches became different
species.
Variation and Adaptation
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Variation- Slight differences in
individual traits.
These variations can lead to
adaptations over many generations.
Adaptation – a variation that improves
the chances for survival.
Example of adaptation - camouflage
Natural Selection
1.
2.
3.
Organisms generally produce more
offspring than can survive.
Differences or variations occur among
individuals of a species.
These variations are passed to
offspring.
Natural Selection
4. Some variations are helpful.
Individuals with helpful variations
survive and reproduce better than
those without these variations.
5. Over time the offspring of individuals
with helpful variations may
eventually become a separate species.
Peppered Moths
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Example of natural selection
Light colored peppered moths vs. dark
colored moths
Pollution from the Industrial Revolution
increased the populations of dark colored
moths.
Darker moths suddenly had an advantage
over lighter moths.
Natural Selection
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Natural selection is sometimes
referred to as:
The Survival of the Fittest
Geographic Isolation
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Sometimes a small part of a
population will get separated from the
whole.
Mountains, lakes or oceans can be
geographic separators.
Over time, the isolated population can
become very different from the
original population.
Speed of Evolution and/or
Natural selection
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Two Theories:
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Gradualism- Long, slow process by
which one species changes into
another species.
Punctuated Equilibrium- Fast form
of evolution by which one species
suddenly changes into another.
Gradualism…
Clues about evolution
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What evidence is available for the
theory of evolution?
1.
2.
3.
Fossil record in sedimentary rock
Embryology
DNA comparison between species
1. Fossils
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Most of the evidence for
evolution comes from fossils.
A fossil is the remains, an
imprint or a trace of a
prehistoric organism.
Most fossils are found in
sedimentary rock.
This type of rock is formed
when sand, silt, clay and mud
are compacted together.
Scientists that
study fossils are
paleontologists
Fossils
Determining a fossil’s age
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Relative dating –younger
rock layers are deposited
on top.
This estimation is made
by comparing the ages of
the rock found above and
below the fossil in
question.
Determining a fossil’s age
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Radiometric dating – this is an age
determining process that uses radioactive
elements to help determine the age of fossils.
Every radioactive element gives off radiation
at a different rate. Half-life = decay of ½ of
the atoms of an element.
Scientists can use this rate to help them
determine an age of a fossil.
This method does not always produce exact
results.
Fossil Record
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The fossil record is incomplete…
Since fossils can’t tell us everything
about evolution other factors are
looked at.
2. Embryology
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Embryology – the study of embryos and their
development.
Structures that resemble a tail, gills or gill slits
are found in fish, reptile, bird, and mammal
embryos.
These structures suggest a similarity among
all vertebrate species.
Homologous structures
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These are body parts that are:
* similar in structure.
* similar in function.
Vestigial structures
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These muscles in
horses are larger
and allow them to
turn their ears
toward noise.
These are
structures that
don’t seem to have
any function.
Scientists
hypothesize that
vestigial structures
are body parts that
once functioned in
an ancestor.
3. DNA
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Scientist compare DNA of different
organisms.
Similar DNA suggests a commonality.
Evolutionists theorize that this
indicates that these species had a
common ancestor.
Evolution states that these
creatures all came from a
common ancestor…
Summary
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Evolutionists hold that:
1. Natural selection occurs:
* only certain individuals in a population
are able to survive and reproduce
* the species that exist today look
different from their ancestors
2. The fossil record, embryology, and
DNA suggest that all animals have
come from a common ancestor.