Transcript Origin of Life

Origin of Life
Theories
Spontaneous Generation
(abiogenesis)- life comes from
nonliving material
Biogenesis- life only comes from
other living things.
Important Experiments
 Francesco
Redi – disproved that
maggots came from dead organisms
 Miller
and Urey
- early atmosphere had very little
oxygen
- used to create organic compounds
(amino acids)
 Louis
Pasteur – completely
disproved spontaneous generation

Lamark’s Explanation
a. believed that traits were
“acquired” and not
determined by genes
b. traits were results from
organisms experiences or
behavior
c. “necks of giraffes”
Charles Darwin’s
Theory of Evolution
 Galapagos
Islands
a. Darwin’s finches
 Origin
of Species by Natural
Selection – by Charles Darwin
 Evolution
– concept that species
have changed over time
Natural Selection
“organisms best suited to their environment
reproduce more successfully than other
organisms”
1. Adaptation
2. Competition
*selection conditions change as the demands of
the environment change
*if change is too extreme and organism can’t
change, they become extinct or die
Patterns of Evolution


Genetic Drift – the alteration of allele
frequencies by chance events
Punctuated Equilibrium – speciation occurs
during brief periods of rapid genetic change



Divergent Evolution – two or more
related populations or species become
more and more dissimilar
- domestic dogs
Convergent Evolution – 2 organisms
seem to be similar but are not at all
- shark and porpoise
Co-Evolution – 2 species evolve together
- plants and the animals that pollinate
them
Types of Natural Selection
3
types
1. stabilizing selection
2. directional selection
3. disruptive selection
 Stabilizing
Selection
- individuals with the AVERAGE
form of a trait have the highest fitness
- most common
 Directional
Selection
- individuals that display a more
extreme form of a trait have a greater
fitness then those with an average
form of trait
- one extreme > average
 Disruptive
Selection
- individuals with either extreme of a
trait have a greater fitness than those
with a average form
- either extreme > average
Evidence of
Evolution
Evidence from Living
Organisms
Homologous and
Analogous Structures

a. Homologous –
similar features that
originated in a
shared/common
ancestor
b. Analogousfeatures serve
identical functions
and look somewhat
alike
 Vestigial
Organs
“useless features”
a. appendix
b. human tailbone
 Evolutionary
Evidence
- similar DNA, homologous features,
vestigial structures
 Biochemical
Evidence
- similar amino acid sequence
 DNA
and Chemical Studies
a. human and chimp DNA – very
similar
 Embryo
studies
a. all vertebrae embryos are similar
at 4 weeks
b. all vertebrates have gill slits at 4
weeks