Darwin and EvolutionDarwin and Evolution

Darwin’s Darwin’s VoyageVoyage

• 1831 Charles Darwin accepted a naturalist position aboard the HMS Beagle.

• 5-year voyage that provided Darwin with many observations.

The The Galapagos Galapagos

IslandsIslands• Darwin’s comparison of animals in South America and

the Galapagos Islands caused him to conclude that adaptation to the environment can cause diversification, including origin of new species.

• Island species varied from the mainland species and from island-to-island.

Darwin’s Darwin’s FinchesFinches

• Finches in the islands resembled a mainland finch, but there were more types.

• Finches varied in nesting sites, beak size, and eating habits.

•Finches posed questions to Darwin:

–Did they descend from one mainland ancestor?–Did islands allow isolated populations to evolve independently? –Could present day species have resulted from changes occurring in each isolated population?

Reality of Reality of Darwin’s Darwin’s FinchesFinches

• Darwin actually studied mocking birds more and couldn’t really explain what was going on with the finches.

• A crew member on the beagle is the one who took samples and organized them by island.

•14 species of finches with different beaks (14th is on the Isla del Coco-Costa Rica).

Blue Footed Blue Footed BoobyBooby

• Blue-footed boobies breed from the Gulf of California south to Peru. 

• Blue-footed boobies have long necks, sharp bills, and bright blue feet.

• The blue-footed booby lives on the open sea except when it is breeding. It breeds on ocean islands. 

Masked Booby Masked Booby (Nasca Booby)(Nasca Booby)

• The largest of the Galapagos Booby.• Masked Boobies are common in the

tropics and subtropics nesting in colonies along cliffs or at the sea edge.

• These are the only boobies in the Galapagos to have an annual breeding cycle, though the cycle varies between islands.

• Mate for life and second egg is always for insurance.

Prickly Pear Prickly Pear CactusCactus

and the and the Land IguanaLand Iguana

• Land Iguanas can grow to 3 ft (1 m) in length.

• The Land Iguanas live in the arid portion of the islands.

• The mainstay of its diet is the Prickly Pear Cactus.

• The cactus provides both food and water for the Land Iguanas who can go without fresh water for a year.

• Part of the adaptation to the drier environment includes a conservation of energy by slow movement.

Marine Marine IguanasIguanas

• These sea-going Iguanas exist only in the Galapagos Islands.

• Living on the black lava shore rocks they have developed into efficient swimmers feeding off shore mostly on marine algae and seaweed.

• The black rocks under the equatorial sun provide needed warmth for the iguanas in the day. At night the iguanas pile by the hundred in order to provide heat for one another.

TortoisesTortoises

• Tortoises can have weights over 500 lbs and shells measuring 59 inches-Galapagos Tortoises are among the largest on earth.

• These land-based turtles are

slow moving and known for their long life span of more than 150 years.

•The Tortoise played an important role in the Theory of Evolution.

•They are the most recognized symbol of the Galapagos Islands.

• There are 10 varieties of Tortoises left. (once used for target practice!)

• Strict Vegetarians• Growth rings on

shell indicate age.• Females have no

voice box.• Horrible listeners

but exceptional sense of smell.

LonesomeLonesomeGeorgeGeorge

• Isla Pinta was once home to thousands of tortoises. • The tortoises were a valuable source of meat to

seaman as they could remain alive in a ship hold for up to a year at sea with little food or other necessities.

• Over the years the tortoise population on Pinta diminished.

• In 1971 the park service found the one remaining Pinta Tortoise. He was named "Lonesome George", because he is the last of his subspecies.

• The Park Service moved 'George' to the Darwin Station where they have made every effort to encourage him to breed with female tortoises from Wolf Volcano on Isabela (Wolf Tortoises were found to be the closest morphologically to the Pinta Tortoises). Yet over the past nearly 30 years of trying, no new tortoises have been born.

Mechanism for EvolutionMechanism for Evolution

• Darwin decided adaptations develop over time; he sought the mechanism by which these adaptations might arise.

• Natural Selection was proposed as the mechanism.

• Because the environment is always changing, there is no perfectly-adapted organism.

• The organisms that are best fit to reproduce will.

Preconditions for Natural Preconditions for Natural SelectionSelection

• Members of a population have random but heritable variations.

• More individuals are produced each generation than the environment can support.

• Some individuals have adaptive characteristics that enable them to survive and reproduce better.

On the Origin On the Origin of Speciesof Species

• Darwin waited over 20 years to publish his works.

• He used the time to test his hypothesis that life forms arose by descent from a common ancestor and that natural selection is the mechanism by which species can change and new species arise.

Evidence for EvolutionEvidence for Evolution

• Evolution is one of the great unifying themes of biology and it is supported by the following evidence:– Fossil Evidence– Biogeographical Evidence– Anatomical Evidence– Biochemical Evidence

Fossil EvidenceFossil Evidence

• Supports the common descent hypothesis

• Fossils can be linked over time because they reveal a similarity in form, despite observed changes.

• Transitional forms reveal links between groups.

Biogeographical Biogeographical EvidenceEvidence

• Biogeography studies the distribution of plants and animals worldwide.

• Distribution of organisms is explained by related forms evolving in one locale and spreading to other accessible areas.

• Finches in Galapagos

Anatomical EvidenceAnatomical Evidence

• Homologous Structures -due to common ancestry.

• Analogous Structures -not due to ancestry but rather similar function.

Anatomical EvidenceAnatomical Evidence

• Vestigial Structures -Structures that no longer serve functions in modern day organisms.

• Embryology

Biochemical EvidenceBiochemical Evidence• Genetic code is the same in all

organisms.

• By evaluating DNA we can make comparisons and draw conclusions about ancestry.

• Cytochrome c