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Evolution
Mincer/Scully
Evolution
• Evolution-The process by which species
change over time, or become extinct.
• Species-All the organisms that can interbreed
and produce fertile offspring, and look roughly
alike.
• Extinction-When all members of a species
have died and that species no longer exists.
Charles Darwin
• Lived in England
• When he was young, he took a voyage on the
H.M.S. Beagle
• They sailed into the Pacific Ocean, to the
Galapagos, and Darwin discovered several
new species, including species of finches that
were found nowhere else.
• This led him to think about why the finches
on the Galapagos would be different than
those in England.
Darwin
• Basically, Darwin said that living
populations change over time because of
changes in their environment.
• Certain individuals are ‘selected’ to breed
because they are better adapted to the
change in the environment.
• He called this process, ‘natural selection’
Evolution-Some terms
• Adaptation-A trait that an organism has
which helps it to survive its environment.
• Natural Selection- The natural change
in environment which will determine
which traits are useful and which are not;
those traits will be passed on to succeeding
generations.
Peppered Moth
• The peppered moth comes
in two colors: white and
black
• The white color is favored
by natural selection,
because the bark of the
trees that the moth rests on
is white. This makes it
hard to be spotted by birds.
Pepper Moth
• However, when the factories in England
started up, the bark of the trees often was
covered in soot. This made the bark of the
trees black. Scientists started seeing the
moth population change from almost all
white to almost all black.
Peppered Moth
• If this had happened long enough, the
moth would have become a new species
that was all black.
Evidence-Observations
• Fossils-Fossils are the petrified bones of
animals and plants that lived thousands to
millions of year ago, e.g. the dinosaurs
• Fossils take a really really long time to
form. There have to be exactly the right
conditions when the animal dies
Evidence-Observation
• Vestigial organs-The appendix is an
organ which is not used for anything in
humans, but is used in many other
mammals, like rabbits to help in the
digestion of food.
Evidence of Evolution
• Homologous Body Structures- Body
structures of different species which look
very similar, if not the same.
Evidence
• DNA!
• Scientists have compared the DNA of
many organisms, and organisms that have
similar structures often have very similar
DNA.
• Humans and Chimpanzees have 98%
the same DNA
How does Evolution Work?
• Genetics!
• Each species has a natural variation,
because of different alleles. When
something in the environment changes,
some traits may provide an advantage,
those traits, and therefore genes, are
passed on to the next generation.
So…
• The genes which code for traits which
help the organism survive are going to be
passed on.
• Those that are not helpful are not going to
be passed on, but eliminated from the
gene pool.
• Over many generations, a new species can
form.
Hardy-Weinberg Principle
• States that gene frequencies will remain constant
unless something causes them to change
• There are five main conditions that need to
remain stable for gene frequencies to remain
stable:
• 1. Random mating must occur
• 2. Population must be large
• 3. No immigration or emigration
• 4. No mutations
• 5. No environmental changes
Speciation
• Behavioral isolation: Occurs when two
populations are capable of reproduction, but
their behaviors force them to not to mate with
each other.
• Geographic Isolation: Two populations are
separated by geographic barriers, like mountains
or rivers, preventing interbreeding.
• Temporal Isolation: When two or more
species reproduce at different times.
Behavioral Isolation
Geographic Isolation
Temporal Isolation
History of Life on Earth
• The pattern seems to be from simpler
forms to more complex forms
• Several mass extinctions of large numbers
of species have caused rapid evolution to
occur,
– eg. 65 million years ago, and the Permian
Mass Extinction
Patterns
• Extinction- 99% of all species who ever lived
are now extinct
• Adaptive Radiation- One species (Or a small
grouping of species) evolves into many
different diverse forms
• Convergent Evolution- When two species
evolve along similar lines, look similar, but
evolved from very different ancestors
• E.g. bird and bats
Patterns of Evolution
• Coevolution- When two species, or groups of
species, evolve together in an ecosystem.
• E.g. flowers and insects
• Punctuated Equilibrium- Long stable
periods of no speciation, with short rapid
changes.
• Changes in developmental genes-Hox genes
(Master control genes) change slightly
(mutation), changing how other genes are
expressed.
Co evolution
Adaptive Radiation
Convergent
Evolution
Extinction