Evolution of an idea Evolution Unit

Look at the toes ...

Immutable & unchanging For a long time, European philosophers and people in general believed all living things were created in their present form. But in the 1700s, some people began to question that idea ...

Seeds of change ... Linnaeus & Erasmus Darwin (Charles’ grandfather) proposed that living organisms must have changed over time, but had no explanation for how First mechanism of evolution proposed by Jean-Baptiste Lamarck.

Jean-Baptiste Lamarck

Jean Baptiste Lamarck (1744-1829) He placed fossils in an evolutionary context and published a theory of evolution in 1809.  His theory used two common ideas of his time: 1) Use and disuse - parts of the body used on a regular basis become larger and stronger; those not used deteriorate.                                   2)  Inheritance of these acquired characteristics (I.e., the modifications) are passed onto the offspring.                         Lamarck’s theory was based on observations of fossils, but gave no mechanism for evolution. 

Inheritance of Acquired Characteristics Still ... most people were skeptical. All species evolve over time. A species evolves in response to its environment & become better adapted to that environment. Changes are passed on from generation to generation (inheritance of acquired characteristics).

Lamarck Today we know that Lamarck’s was flawed Ex – your vision does not improve the more you use your eyes It is possible to stretch your neck slightly, but it will not alter you DNA and your children will not be born with longer necks

Lamarck - Contributions All species evolve over time A species evolves in response to its environment and becomes better adapted to that environment Changes are passed on from generation to generation

What about fossils? Georges Cuvier (1769- 1832) noted the following ... Fossils of simple organisms are found at all depths ... but more complex organisms are only found at shallower depths. Fossils in the shallowest depths are more likely to resemble living species.

What possible explanation could there be?

Catastrophism Cuvier explained the fossil record by suggesting that a series of catastrophes had caused widespread extinctions, i.e., species did not change

Meanwhile ... Charles Lyell was about to change everything.

Uniformitarianism James Hutton: concluded from studies on erosion and sedimentation that it took millions of years to form Earth's landscape. Charles Lyell (British lawyer & geologist) in 1830 expanded on Hutton's idea and found more evidence that suggested that geological changes are slow and gradual. Controversial because it suggested that the Earth was very old & that slow processes could result in large changes such as formation of mountain ranges

Fossils Also, palaeontologist Georges Cuvier's work on fossils showed that different species existed in the past. This supported the theory that life had evolved from simple to more complex forms over time. humananatomy1.blogspot.com

Fossil Evidence

These discoveries set the stage for Darwin…

Charles Darwin’s Voyage From 1831-1836, Charles Darwin toured the world in the HMS Beagle gathering thousands of organisms amazing diversity of life

The Galapagos Islands The Galapagos Islands, 18 islands that were formed from volcanoes that rose up from the ocean floor were his discovery

The Galapagos Islands

The Galapagos Islands

Darwin’s Observations 1. Species Vary Globally distantly related species living in similar habitats in different parts of the world looked similar and acted similar Ex: Emus, rheas, and ostriches 2. Species Vary Locally Related animal species that occupied different habitats within a local environment had different features. Ex: Islands (turtles, finches) 3. Species Vary over Time Fossil evidence (Ex: armadillo and glypotodon)

Darwin’s Finches

The Theory of Evolution States… All living things share a common ancestor Species evolve over time via the mechanism of NATURAL SELECTION (descent with modification) where individuals with inherited characteristics best for their ecological niche will have more offspring Survival of the fittest!

Natural Selection (based on observations)... Struggle for existence. Most organisms reproduce in excessive numbers but resources are limited = COMPETITION Variation: differences among members of the same species (hair colour etc.) and certain differences = greater reproductive success and many were heritable. Role of Environment: survival based on how well it suited it’s environment.