Darwin’s Theory of Evolution

What is a scientific theory? A well substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment.

The Puzzle of Diversity Evolution ◦ Change over time ◦ Change in the inherited characteristics of populations over successive generations.

Evolution how ◦ Mutations that result in better chance for survival  Traits are passed on to offspring

The puzzle of diversity Charles Darwin ◦ Largest contributor to current understanding of evolution ◦ Voyage of the H.M.S. Beagle  Collected samples of life in different parts of the world. ◦ Galapagos Islands  Patterns of diversity  Fossils

Voyage of the Beagle

Galápagos Islands

Galápagos Species Turtles ◦ Different length necks ◦ Different shells ◦ Work perfectly for the island on which they live

Galápagos Species Finches ◦ Different beaks ◦ Different colors ◦ Traits correlate to environment

Artificial Selection If we can change a species through our choosing, why could nature not choose and change? Humans choose which organisms survive and reproduce

Thomas Malthus 1798 Human populations will out grow space and food supplies. Can you see this theory at play today?

Natural Selection Some organisms in the fight for life are better equipped than others Those best equipped will survive

Natural Selection Some organisms in the fight for life are better equipped than others Those best equipped will survive

Natural Selection Principles on pg 422

Ideas That Shaped Darwin’s Thinking Influences on Darwin’s Thinking ◦ James Hutton (1785)  Geological forces shaped Earth.  Earth millions of years old, not thousands.

How are mountains formed?

Tectonic Plates

Are Scientific Discoveries Unique? Alfred Russel Wallace

Influences on Darwin ◦ Jean-Baptiste Lamarck (1809)  Living things have changed over time ~ all species descended from other species.  Species are adapted to their environment.

Jean-Baptiste Lamarck Organisms acquired or lost certain traits during their lifetime. These traits could be passed on to their offspring. 3 parts to this idea…

Tendency Towards Perfection All organisms seek perfection Acquire traits that help them flourish ◦ Birds’ desire to fly led to flight

Use and Disuse Change parts of body through use and disuse Bird tries to fly, wings develop over time ◦ Bird does not fly, wings fall off over time Tie an arm behind your back…

Inheritance of Acquired Traits Gained during an organism’s lifetime ◦ Body builders, strong heart, obesity Traits passed directly to offspring ◦ Since I run a lot, my child will see the advantage Epigenetics?

Evaluating Lamarck was wrong; so, what did he contribute? Laid the foundation for evolutionary theory First to document that organisms adapt to their environment

Influences on Darwin ◦ Charles Lyell – Principle of Geology  Past events must be explained using processes that can be observed.  Slow process ~ These processes are still occurring! ◦ Robert Frost once said,  “In three words I can sum up everything I know about life: it goes on.”

Stop, collaborate, and listen… Could one person come up with and completely legitimize a theory on his/her own? Could Darwin have drawn the picture of Evolution all by himself? ◦ Who were four of the main contributing artists to his first proposal?

Darwin Presents His Case Publication of On the Origin of Species ◦ Inherited Variation ◦ Artificial Selection ◦ Natural Selection  Struggle for existence  Fitness and Adaptation  Survival of the Fittest  Natural Selection  Descent with modification  Common descent

15-3: Darwin Presents His Case Publication of On the Origin of Species ◦ Evidence  Fossil record  Geographic distribution  Homologous body structures  Vestigial organs  Similarities in Embryology Strengths and Weaknesses of Evolution