Transcript Evolution Powerpoint

Evolution
• What is evolution?
– It is the process of biological change by which
descendents come to differ from their ancestors
Scientists
• Scientists who began studying evolution:
– Linnaeus (1700’s)
• Developed classification system of organisms
• Proposed that organisms arose from hybridization
Scientists
• Buffon (1700’s)
– Used evidence of past life
– Proposed that species shared ancestors instead of
arising separately
– Proposed earth was much older than 6000 years
Scientists
• Erasmus Darwin (1731)
– Proposed all living things were descended from a
common ancestor
– Later expanded upon by his grandson
Scientists
• Lamarck (1809)
– Didn’t believe in
extinction
– Species evolved instead
– Proposed that changes
in environment caused
behavior to change
– Organism passes on
these traits to offspring
– “Inheritance of acquired
characteristics”
Charles Darwin
• Darwin took a trip to
the Galapagos Islands
aboard the HMS Beagle
• He studied the
inhabitants of the island
What did Darwin find?
Charles Darwin
• Findings and
conclusions:
– Variation among species
– Led him to believe
species adapt to their
environment
– Adaptation- feature
allows an organism to
better survive in an
environment
– Leads to change in
populations over time
Examples of Adaptations
horned lizard
pistol shrimp
aye aye
archer fish
Charles Darwin
• Natural Selection
– Individuals inherit beneficial adaptations and
produce more offspring than others
Charles Darwin
• 4 principles of natural selection:
1. Variation
- Differences among organisms
2. Overproduction
- More offspring increases chance for survival
3. Adaptation
- Certain variations allow to survive better
4. Descent with Modification
- Over time, more individuals in the population will
have the beneficial traits
Natural Selection
Variation
Adaptation
Overproduction
Descent with Modification
Fossil Evidence
• No fossil evidence that
contradicts evolution
has been found
• Allows us to see
transitions of species
over time
Anatomical Evidence
• Homologous structures
– Features that are similar
in structure, but
different in function in
different organisms
– Supports common
descent
Anatomical Evidence
• Analogous structures
– Structures that perform
similar function
Anatomical Evidence
• Vestigial structures
– Unused features
– Structure had a function
in early ancestor
– Helps support common
ancestry and evolution
Molecular Evidence
• All living things have
DNA
• Organisms carry
pseudogenes
– Genes that do not
function (vestigial)
• Cells have very similar
proteins
– Marine worms have
same proteins in the eye
as vertebrates
 Comparison of milk protein in
whales and hippos:
• Hippo
TCC TGGCA GTCCA GTGGT
• Humpback Whale
CCC TGGCA GTGCA GTGCT
Match the structure
Homologous, analogous, or vestigial
B
A
C
Population Distributions
• Normal Distribution
– Frequency of a certain
phenotype is near the
mean
Population Distributions
• Directional Selection
– Selection favors
phenotypes at one
extreme
– Population shifts toward
advantageous trait
Population Distribution
• Stabilizing Selection
– The intermediate is
favored and becomes
the most common
Population Distribution
• Disruptive Selection
– Both extreme
phenotypes are favored
Genetic Drift
• Bottleneck Effect
– Occurs after an event
greatly reduces the size
of a population
– Ex. Overhunting of
elephant seals
Genetic Drift
• Founder Effect
– Occurs after a small # of
individuals colonize a
new area
– Ex. Emerald ash borer
Sexual Selection
• Occurs when certain
traits increase mating
success
• Two types:
• Examples:
– Intrasexual
– Intrasexual
• Physical competition
among males
– Intersexual
• Displays among males
Giraffe
fight
Bird
display
– Intersexual
Long-tailed Widowbird
Male
Female
Evolutionary Classification
• Cladogram
– Evolutionary tree that
proposes how species
may be related to each
other through common
ancestors
• Clade
– Group of organisms that
share certain traits
Evolutionary Classification
Cladogram for modes of transportation:
Bicycle
Car
Motorcycle
Airplane
On foot
walking
bicycle
motorcycle
car
airplane
wings
motor
wheels
Passengers
enclosed