EVOLUTION

Charles Darwin & the theory of Natural SelectionBlue Book: Ch. 13

• English Naturalist• 1859 published On The Origin of Species• Served as a naturalist on the HMS

Beagle and traveled around the world over 5 years observing.

Charles Darwin

Darwin’s Observations1. Observed fossils of extinct

armadillos in South America.

2. Visited the Galapagos Islands, and was intrigued by the fact that many plants & animals resembled those found on the coast of Ecuador.

3. Read about how populations can not simply keep growing, that there is balance due to death.

Ideas That Influenced DarwinArtificial Selection:

Selective breeding of plants and animals to pass desirable traits to the offspring.

Ideas That Influenced Darwin: Lamarck vs. Darwin

• Individuals try to improve themselves.

•Effort to improve causes those body structures to develop and others to disappear. (Theory of Use & Disuse)

•Transmission of acquired characteristics (that offspring would receive the changed trait).

• Variation in a population.

•Some variations are favorable improving the organisms ability to survive & reproduce. (Natural Selection)

• Over time, the favorable traits (adaptations) will spread in future populations.

•Over long periods of time, small changes accumulate. (Gradualism)

Evolution by Natural Selection1. VARIATION IN A POPULATION

There are slight differences between organisms of a species.

2. CHALLENGE IN ENVIRONMENTSome individuals are better suited to survive in an environment. Some traits are beneficial, some are not.

3. SURVIVERS REPRODUCE & COMPETEOvertime, the organisms with the beneficial trait survive and reproduce passing on the favorable trait to the offspring.

4. FAVORABLE TRAITS PASS ONThe number of individuals with the beneficial trait increase in a population, and over long periods of time these changes accumulate. Populations evolve.

Evidence of Evolution: Fossil Record

• Fossils = Preserved or mineralized remains or imprint of an organism.

Evidence of Evolution: Fossil Record

Fossils Formation: (See D. Attenborough Video)

Ancestor of Birds!

Evidence of Evolution: Anatomy & DevelopmentHomologous Structures: Structures that share a common ancestry.

Evidence of Evolution: Anatomy & DevelopmentVestigial Structures: A structure that may have had a function in an ancestor, but no clear function in the modern species.

Evidence of Evolution: Anatomy & Development

Embryology = The study of embryos to understand the evolutionary history of an organism.

Evidence of Evolution: Molecular Biology

The study of protein sequences to understand the evolutionary history of an organism.

Species• Species: a population whose members can

breed and produce fertile offspring.

Ligers are not fertile! Proving that Lions & Tigers are separate species

Species

Mules are not fertile! Proving that horses & donkeys are separate species!

Speciation• Speciation: The formation of a new species;

occurs when members of the same species become isolated and can no longer reproduce.

Speciation• Reproductive Isolation: The separation of a

species or population so that members can no longer interbreed.– Geographic isolation

– Behavioral isolation

– Temporal (timing) isolationMale cardinal - YouTube.flv

Tempo (Rate) of Evolution• Gradualism – gradual

changes over a long period of time that leads to the formation of a species.

• Punctuated Equilibrium Rapid changes in species separated by periods of little or no change.