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