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Evolutionary TheoryThe Theory of Evolution is based on many types
of data.
Fossil Record
Morphological Evidence
Embryological Evidence
DNA Evidence
Homologous StructuresBody parts with
the same structures but have different functions
Analogous StructuresBody parts with
similar functions but with different anatomy (not good evidence)
Vestigial StructuresBody parts that are
reduced in size and are no longer used
Hip bones in snakes have no purpose, but they suggest that snakes evolved from ancestors with hips
Embryological StructuresDifferent
species have similar embryos
At certain stages of development many animal embryos are difficult to identify
Theories of EvolutionJean Baptiste Lamarck (1744 –
1829)
Theory of Acquired Characteristics
1. Living species descended from a common ancestor (True)
2. Acquired characteristics could be passed on to offspring (False)
-an acquired trait is one that is not determined by genes.
Ex.-birds’ feet, giraffe necks
Charles DarwinDarwin (1809 -
1882)
Darwin studied many animals but the finches from the Galapagos Islands were of great interest to him.
The Journey
Galapagos Islands
FinchesFinches on
different islands had different characteristics.
It is thought that a single species from S. America flew to the islands and the different islands caused the finches to evolve.
. Charles Darwin (1830)
1. Overproduction2. Struggle for existence
(survival)3. Variation 4. Survival of the fittest5. Natural selection6. Evolution of new species
Natural SelectionThe environment
selects the most-fit organisms.
The environment selects organisms with beneficial traits
Natural SelectionVariation exists within a species
Among members of a species, traits vary
Natural selection is based on . . .
Non-random survivalAlbino squirrels
Non-random matingMate selection
Woman’s choice
Non-random fecundityProduction of offspring
Advantageous Traits/Adaptations
MIMICRY- advantage gained by copying the appearance of another, more dangerous, species.Ex.- flies and hornets
CAMOUFLAGE- advantage gained by blending in w/ surroundings.Ex.- walking stick, tiger, leaf fish, etc.
Types of Natural SelectionStabilizing
Selection -
Individuals with the average form of a trait have the highest fitness
Types of Natural SelectionDirectional
Selection -
Extreme forms of a trait are more fit
Types of Natural SelectionDisruptive
Selection -
Either extreme form of a trait is more fit.
Patterns of EvolutionCoevolution
The change of two or more species in close association with each other
Parasites & host, predator & prey
Patterns of EvolutionConvergent
Evolution
The environment selects similar phenotypes even though the organisms are quite different
Sharks and dolphins
Patterns of EvolutionDivergent
Evolution
Two or more related populations or species become more and more dissimilar.
Galapagos finches