Happy Birthday Mr. Darwin

What concepts did Darwin develop, and why were they so revolutionary?

Species can change- Living things are not fixed, but can change over many generations.

Common Descent—All life on Earth shares a common ancestry. Yes, even humans.
Drawing from one of Darwin's notebooks

Gradualism--The change of a species takes a long time.
Marine Iguana, Isabela Island, Galapagos

Land Iguana, North Seymour Island, Galapagos.
The land iguana and marine iguana evolved from a common ancestor, probably an iguana from the mainland of South America.

Natural selection
Certain randomly acquired traits are helpful.

Individuals with helpful traits survive longer, have more offspring, so over time these traits increase in a
population.

Nature selects which traits are beneficial, and which are not.

Small ground finch, San Cristobal Island, Galapagos

Medium ground finch, San Cristobal Island, Galapagos.

The main difference between "Darwin's finches" is the size and shape of their bills. What advantage would their be to an individual with a beak like the one found on the medium ground finch? What about the the bill found on the small ground finch?

Others prior to Darwin had suggested species may have changed over time, and were not fixed. However, Darwin was the the first to suggest a logical mechanism (natural selection) though which these changes occurred.

Happy Darwin Day

Have you googled today? If you have then you might have noticed the tribute to Mr. Dawin. I see some of "Darwin's finches", from the Galapagos Islands in the illustration. When Darwin collected the birds, he actually thought he had a mix of finches, blackbirds, and warblers only to discover after the birds were examined back in England, by ornithogist John Gould that indeed they were all finches.

The bird that really go his attenion in the Galapgos were the mockingbirds on different islands.

Darwin wrote in The Voyage of the Beagle:
"My attention was first thoroughly aroused, by comparing together the numerous specimens, shot by myself and several other parties on board, of the mocking-thrushes, when, to my astonishment, I discovered that all those from Charles Island belonged to one species (Mimus trifasciatus); all from Albemarle Island to M. parvulus; and all from James and Chatham Islands (between which the other two islands are situated, as connecting links) belonged to M. melanotis."

He also noticed that the different species did not occur together on the various islands he visited and he wondered why this was...

Darwin Day Special: Links

I've come across a couple of websites of interest to those of you who wish to learn a bit more about Charles Darwin.

This site by David Leff, has an amazing amount of information about Darwin the man as well as Darwin the scientist.

The complete works of Charles Darwin are online. This is a wonderful resource for exploring some of his letters, books and other publications

David Attenborough's new program: Darwin and the Tree of Life--

My favorite natural historian, Sir David Attenborough has developed a new program about Darwin and evolution. I am not sure when it will be broadcast, but I imagine it will be ready by the 200th anniversary of Darwin's birth which is Feb. 12.
Take a look at this short interview of Sir David for a preview of the coming show.