Evolution week 1 Darwin’s Theory & Natural Selection

Evolution  Nothing in biology makes sense without the unifying concept of evolution!

Darwin Developed a theory of Evolution  A new view of life came into focus in 1859, when Charles Darwin published his book The Origin of Species.  On its grandest scale, evolution is all of the changes that have transformed life over an immense time.  In a sense, evolution is the biological history of life on Earth.

Before Darwin  Before Darwin there were two ideals about life on Earth 1. One was that species were fixed, or permanent 2. The other was that the Earth was less than 10,000 years old and also relatively unchanged. These ideals were challenged as people became aware of the incredible diversity of organisms past and present, and the nature of Earth’s geologic processess. These ideals were challenged as people became aware of the incredible diversity of organisms past and present, and the nature of Earth’s geologic processess.

In the 1700’s  The study of fossils led by French naturalist Geoges Buffon suggested that the Earth might be much older.  Another scientist of the time – Lamarch, was the 1 st to suggest that similarities between species are because they evolve. His explanation was ultimately flawed. Use and disuse. Use and disuse.

Use or disuse Lamarch also thought that living things might have evolved. But, his reasoning was flawed in that he thought that acquired characteristics could be passed down from parent to offspring.

Voyage of the Beagle!  On a cold December day in 1831, the HMS Beagle set sail from England on a voyage around the world.  The main mission was to chart poorly known stretches of S. America for the British navy.  Aboard was a 22-year old college graduate, Charles Darwin. There to study the geology, plants and animals encountered on the trip.

Darwin’s Observations  Plants and animals throughout the continent all had a definite south American character.  Some of the fossils were gigantic forms of modern animals.  His observations supported his idea that species living in S. America today were descendants from ancestral species on that continent

The Galapagos  The Galapagos are a chain (archipelago) of young islands 900 km of the west coast of Ecuador, S. America.  The Islands had similar plant and animal species to those found on the mainland.  Yet, these organisms were different from island to island.

Blue footed boobies (bobos ~ clown)

Marine & land iguanas

Ahhh!!!

Neck-size vs. Vegetation height

Galapagos’ Finches

Darwin’s Two Main Points  Species of organisms living on Earth today descended from ancestral species. They spread in to different habitats where they accumulated different modifications (adaptations) to diverse ways of life. (Descent with modification)  Natural Selection is the mechanisms for evolution. Natural selection is the process by which individuals with inherited characteristics well-suited to the environment leave more offspring on average than do other individuals. As time passes, populations change through time….they evolve!As time passes, populations change through time….they evolve!

Summary of the Theory of Evolution  DNA is the blue-print for building ALL living things on planet Earth.  DNA sequences are changed by random mutations, radiation, viruses, chemicals, sexual reproduction, migration, geological events, etc.  As a result there is variation within populations of a species.  Those individuals of a particular species with a phenotype (as a result of their genotype) that is more fit to survive in a given environment has a better chance to reproduce.  Those individuals who reproduce more pass-on their genes at a higher frequency than those who do not.  Given enough time anything is possible!!! (Earth is 4.6 billion years old)

The End Bring book tomorrow for a grade!!!