Download Evolution-ppt

E
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L
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T
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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
 Jean Baptiste de Lamarck (1744-1829)
 Theory: Similar species descend from a
common ancestor (evident in fossil record)
To Explain how species change he hypothesized:
 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
Acquired Trait
Example: giraffes
evolved their long
necks by each
generation
stretching further
to get leaves in
trees and that this
change in body
shape was then
inherited.
CHARLES DARWIN (1809-1882)
 Darwin was recommended to be a
naturalist on the ship H.M.S. Beagle
 Sailed around the World in Beagle for five
years-collected specimens and recorded
lots of data
Voyage of the Beagle
 Darwin reasoned that Earth is dynamic,
constantly changing –earthquakes,
volcanoes, mountain formation Changes are a long slow processorganisms must adapt to changes or ?
The study of the Galapagos
finches led Darwin to his TWO
theories!
Darwin’s Theories
Descent with Modification
 Newer forms appearing in the fossil record are
modified descendents of older species
 All species had descended from one or a few
original types of life
Descent With Modifications - tree of life
that links all living things!
Modification by Natural Selection
Describes how evolution occurs!
1. Living things face a constant struggle for
existence
**organisms in nature produce more than
can survive**
2. Variation exists within populations:
- mutation
- Crossing Over/Independent
Assortment (make different gametes)
- Sexual reproduction - Random fusion
of two gametes
**POPULATIONS
HAVE
VARIATIONS**
Through
mutation
three
variations
of neck
length
exist:
Short,
Medium
and long
necks.
3. Non-random Survival and Reproduction
-Individuals with traits best suited to their
environment (favorable traits) survive and
reproduce in high numbers
** SOME VARIATIONS ARE FAVORABLE**
-Having a high number of favorable traits gives
the organisms an adaptive advantage
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)
**SURVIVORS HAVE FAVORABLE TRAITS TO
PASS TO OFFSPRING**
- Fitness: organisms ability to survive and pass
on its genes
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 ...
Outcomes of Natural Selection
Natural Selection can alter variation in
a population in three ways:
 Most traits resemble bell curve for
phenotypes
Stabilizing Selection
 Favors individuals with the average
phenotype of the trait (average form have
the highest fitness)
Directional Selection
 Environmental conditions favor individuals
of one extreme phenotype
Disruptive Selection
 Environmental conditions favor individuals
of both extremes of the phenotype.
 Can lead to creation of a new species
Evidence of Evolution
Homologous
Structure
Analogous
Structure
Vestigial
Structure
Same
Structure
Different
Function
Same
Function
Different
Structure
Reduced
Function
of
body part
similiar
embryos
similar
DNA
incomplete
record
of life
on Earth
Similar
amino acids
and
proteins
Law of
Superposition
New layers on
top of old layers
Evidence of Evolution
Comparative
Anatomy
Homologous
Structure
Analogous
Structure
Vestigial
Structure
Same
Structure
Different
Function
Same
Function
Different
Structure
Reduced
Function
of
body part
Embryology
Molecular
Biology
Fossil
Record
similiar
embryos
similar
DNA
incomplete
record
of life
on Earth
Similar
amino acids
and
proteins
Law of
Superposition
New layers on
top of old layers
Evidence of Evolution
Comparative Anatomy
Homologous Structures: same structure but
different function
Evidence of Evolution
Comparative Anatomy
 Analogous Structure
- same function but
different structures
Evidence of Evolution
Comparative Anatomy
Vestigial Structure - body part that is
reduced or has no use
Evidence of Evolution
Embryology
Evidence of Evolution
Fossil Record
Evidence of Evolution
Molecular Biology
Patterns of Evolution
Ways species change to adapt to their
habitats:
o Coevolution
o Convergent Evolution
o Divergent Evolution
Patterns of Evolution
Coevolution: Two or more species change
together!
Examples:
1) Predator/Prey
2) Plant and pollinator
Patterns of Evolution
Convergent: Two dissimilar species
becoming similar
Environment selects for similar
phenotype (but ancestors were
different)
Patterns of Evolution
Divergent: Two similar species become
dissimilar in response to environment