Transcript Intro to Evolution

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Questions to Ponder
TRUE/FALSE
1. You can web your hands if you try.
2. You can acquire traits in your lifetime that will
help you survive.
3. All organisms have the same chance for survival.
4. All organisms need the same favorable trait.
5. Evolution of most organisms occurs during their
lifetime.
THEORIES OF EVOLUTION:
LAMARCK VS. DARWIN
• Lamarck (1744-1829)
• Darwin (1809-1882)
LAMARCK’S THEORIES: wrong
Lamarck (1744-1829)
• Acquired trait: a trait NOT determined by
genes, it arises during an organisms lifetime
as a result of behavior and can be passed
onto offspring
WRONGLamarck: Acquired Trait
Example: giraffes
evolved their long
necks by stretching
further to get leaves
in trees and that
this change in body
shape was passed
on.
CHARLES DARWIN (1809-1882)
voyage of the Beagle
The study of the Galapagos
finches led Darwin to his TWO
theories…
1) Decent With Modification
2) Natural Selection
Darwin’s Theories
1) Descent with Modification
• Newer forms appearing in the fossil record are modified
descendents of older species
• All species had descended from one common ancestor
Descent With Modifications - tree of life that
links all living things!
Modification by Natural Selection
Describes how evolution occurs
organisms in nature produce more than can survive
1. THEREFORE living things face a constant
struggle for existence
POPULATIONS HAVE VARIATIONS
2. Variation exists within populations because:
- mutation
- Crossing Over/Independent
Assortment (make different gametes)
- Sexual reproduction - Random fusion
of two gametes
Through mutation three
variations of neck length
exist: Short, Medium and
long necks.
Let’s review Mutations
SOME VARIATIONS ARE FAVORABLE
Having a high number of favorable traits gives the
organisms an adaptive advantage
3. Non-random Survival and Reproduction
-Individuals with traits best suited to their environment
(favorable traits) survive and reproduce in high numbers
The long neck giraffe has the
“best advantage” and
therefore reproduces more
than the others
4. These favorable traits have to be heritable (able to
be passed down to offspring)
- Fitness: organisms ability to survive and pass on
its genes
SURVIVORS HAVE FAVORABLE TRAITS TO PASS TO
OFFSPRING
Long neck
giraffes have
baby long
neck giraffes
5. Adaption: The number of organisms with
favorable traits increases
Populations genetically change to become more
suited to the environment
The entire
population of
giraffes now ALL
have long necks
POPULATIONS
CHANGE OVER
TIME
Summary:
• Natural selection is not an active process: the
environment “selects” the traits that are
favorable and those that are not
• If the environment changes, so must the
...population
**The environment decides which alleles are
favored not the individual**
Evidence of Evolution
1) Fossil Record
Evidence of Evolution
Comparative Anatomy
Homologous Structures: same structure but
different function
Evidence of Evolution
Comparative Anatomy
Analogous Structure:
Same function but
different underlying
structures
Evidence of Evolution
Comparative Anatomy
Vestigial Structure - body part that is
evolutionarily reduced or has no use
Evidence of Evolution
Embryology
Evidence of Evolution
Molecular Biology