What is Evolution?
• A change in an organism over time
• Process in which modern organisms
have descended from ancient organisms
• Populations evolve, NOT individuals
Who was Charles Darwin?
• A scientist that lived in
the 1800’s
• He was a Naturalist
• He came up with the
Idea of Evolution by
Natural Selection
What did Darwin Accomplish?
• Sailed on the H.M.S Beagle
– Collected fossils & made observations from
around the world
• Wrote the book On
The Origin of Species
What did Darwin find on the
Galapagos Islands?
• The Animal Species on the Galapagos Islands
live no where else in the world.
• Each island had different climates, species, and
food sources.
• Darwin wondered if the species living on the
different islands were once all part of the same
species
Darwin’s Route:
How do Organisms Change Over
Time?
Through
Natural Selection &
Artificial Selection.
What is Artificial Selection?
• Selection done on purpose by humans for
breeding useful traits into different
organisms
EX: Breeding Dogs for
certain fur color
Breeding faster Race
Horses
Creating bigger fruits
& vegetables
What is Natural Selection?
• The Process in which individuals that are
better suited to their environment survive
and reproduce most successfully
How did Darwin’s Finches show
Natural Selection?
• There was a
different type of
Finch on each
island.
• Each type of
Finch had a
different beak.
Why were the beaks different?
• Each island had different types of food
(seeds, flowers, etc.)
• The Finches on each island adapted to the
food that was available to them
• Each Island’s Finches evolved over time to
having different size and shape beaks
that were best suited for the different
island environments.
What did this all lead to?
• Finches with beak differences allowed them
to…..
– Successfully feed
– Successfully compete
– Successfully reproduce
This led to Natural Selection
What 4 Things Must be Present for
Natural Selection to Occur?
1. Genetic Variation
2. Overproduction
3. Competition
4. Survival of the Fittest
What is Genetic Variation?
• Variations that come from DNA
mutations and gene shuffling between
homologous chromosomes that result
from sexual reproduction.
What is Overproduction?
• Organisms reproducing more than
the environment can handle.
• Some organisms
survive while others
do not.
• Overproduction
leads to competition
What is Competition?
The struggle for
existence
– Organisms
compete for
food, living
space and
mates.
Male Frogs Competing for a Female Frog.
What is Survival of the Fittest?
Individuals that are better suited to their
environment are the ones that survive to
reproduce.
What Evidence Supports
Darwin’s Ideas?
•
•
•
•
•
Fossil record
Comparative anatomy
Vestigial organs
Comparative embryology
Molecular biology
Discuss the
Fossil Record
• Fossils are the preserved remains of ancient
organisms
• The Fossil Record provides evidence about
the history of life on Earth
– Most fossils form
in sedimentary rock
How are fossils dated?
• Relative dating is a
method of determining
fossils age by
comparing its
placement with other
fossils in rock layers
– Doesn’t show exact age
of fossil
Relative Dating
• Fossils that are found in a lower layer are older
than fossils that are found in a higher layer
What is Radioactive Dating?
• A technique to calculate the age of fossils
based on the amount of remaining
radioactive isotopes it contains
Age of fossil is
based on halflives
What is a Half Life?
• The length of time required for half of the
radioactive atoms in a sample to decay
For Example:
– Carbon-14 has a half life of 5,730 years
– So if you start with 100 grams of Carbon-14, you
will only have 50 grams left after 5,730 years!
What is Comparative
Anatomy?
• Comparing the parts of organisms for
similarities in structure and function to see
if the organisms came from a common
ancestor.
What are Homologous
Structures?
• Structures of
different animals
that are made
up of the same
parts but have a
different function
What do Homologous
Structures prove?
• This gives evidence of common ancestry
What are Analogous Structures?
• Structures that are made differently, but have
the same function
EX:
Wings of
a bug,
bird and
bat
What is a Vestigial organ?
• Structures that were functional in your
ancestors, but are no longer used in the body
• Structures that serve little or no function
• Structures may be reduced in size
• Shows Evidence of change over time
What are examples of Vestigial
Organs?
• Pelvic Bone in Whales
• Wisdom Teeth in Humans
• Appendix in Humans
What is Comparative Embryology?
• Comparing the formation and
development of embryos of different
species.
Comparative Embryology
What does this show us?
• Early stages of development in many
vertebrates are very similar
– shows common ancestry
– human embryos have gills and a tail
• They have the same:
– Development order
– Similar tissues and organ
structure
Born with a
Human Tail !
Very Rare – Less than
40 Cases Ever
Recorded
What is Molecular Biology?
• The study of the Genes of organisms to see
if they show important similarities at the
DNA level
• DNA similarities can show evolutionary
relationships
• The greater the similarities in DNA, the more
related they are
Who are we related to?
• The genome of Chimps and
Humans are 96% similar –
which means chimpanzees
have 96% of the same DNA
as us!
Despite the similarities,
scientists still
identified 40 million
differences among the
three billion DNA
nucleotides, in each
genome.
What are some other Theories
of Evolution ?
1. Gradualism (James Hutton )
2. Uniformitarianism (Charles
Lyell)
3. Acquired Characteristics
(Lamarck)
What is Gradualism?
• James Hutton (1700’s)
• Said that Changes on Earth formed slowly
but were continuous
• These changes take millions of years
• What did this tell Darwin?
– If the Earth could change over time, then
organisms could have changed over time
What is Uniformitarianism?
• Charles Lyell (1800’s)
• Geologic processes have
not changed throughout
Earth’s history – they’ve
remained constant
• Ex: erosion, & volcanoes
have occurred and still
occur
Who was Lamarck?
• The first scientist to say
that organisms change over
time
• Proposed how specific adaptations
evolve in organisms
What are Lamarck’s Theories on Evolution?
• 1.) Use and Disuse Theory: you could alter
the size or shape of body structures by using
them in new ways
– If you don’t use it, you lose it!
EX: Wings of
birds such as
Ostriches &
Penguins who
don’t have wings
to fly anymore!
Lamarck’s Theories Continued:
2.) Acquired Characteristics: his idea that
an organism can pass on characteristics
that it acquired during its lifetime to its
offspring
EX: Neck of Giraffe
Lamark’s theory of Acquired
Characteristics
Lamarck’s
theories are
INCORRECT
What are Patterns that are seen
in Evolution?
1.)
Extinction • Is the total
disappearance of a
species
• Usually happens
because of
competition for
resources and habitat
99% of all species
that have ever
lived are extinct
2.)
Coevolutionwhen 2 species
evolve in response to
changes in each
other & they depend
on each other for
survival
•
For Example:
Bumble bees pollinating
flowers
& the Acacia Ant living
on the Acacia Tree
3.) Adaptive Radiation
• When one
common ancestor
develops into
many species
• each adapts to a
different
environment
For Example:
Darwin’s Finches & the California Salamanders
(Click for video)
4.) Convergent Evolution
• When distant related species evolve
similar features
For Example:
Swimming appendages: dolphins, sharks
& reptiles
What are 3 Ways Natural
Selection can Affect Phenotype
Distribution?
Directional Selection
Organisms at one extreme or the other survive better than
the others.
An Example: In this habitat, the Birds with Large beaks are able to
survive better than the birds with Small or Medium Beaks
Key
Directional Selection
Directional Selection
More Live; they
can get food
Food becomes scarce.
More Die, they
can’t get food
Large
Stabilizing Selection
• Organisms in the
middle of the curve
have a higher survival
rate
• For Example:
More birds survive that
are born with a medium
birth weight than those
born with a heavier or
lighter weight birds
Stabilizing Selection
Key
Stabilizing Selection
Low mortality,
high fitness
High mortality,
low fitness
Birth Weight
Organisms at
each end, or at
the extremes,
have a lower
chance of
survival
Disruptive Selection
• More organisms at the upper and lower ends
of the curve survive better than those near the
middle
• For Example:
Birds with small and large beaks
have a higher survival rate than birds with a
medium beak
Disruptive
Disruptive
Selection
Selection
Low mortality,
high fitness
High mortality,
low fitness
Population splits
into two subgroups
specializing in
different seeds.
Beak Size
Number of Birds
in Population
Key
Number of Birds
in Population
Largest and smallest seeds become more common.
Beak Size