What’s Natural Selection?

We’ve all heard about Charles Darwin and his voyage on the HMS Beagle. He looked at some finches. He found out about natural selection. He wrote a book. What was it called?

The Origin of the Species.

It was much more than that. Darwin didn’t suddenly get the idea of evolution in his head after gawking at some animals. Darwin knew about the study of fossils (evidence of past organisms) and strata (layers of rock that cover fossils over time). So he had context before he set foot on the HMS Beagle.

He loved looking at nature even as a kid. After dropping out of medical school to go to Cambridge, Darwin, a protegé to John Henslow, met Captain Robert Fitzroy of the HMS Beagle.

They set off to their journey December 1831. Fitzroy wanted to document the shorelines of South America, but Darwin had other plans. Most the time, Darwin observed nature. While observing (he was a naturalist) he made some startling discoveries.

Darwin noticed that animals and plants were right for their environments.
He found out that organisms who lived in South America looked like other animals and plants in temperate places of Europe.

Darwin also discovered fossils that didn’t look like the organisms who lived in South America.

Returning the original quest, Darwin did explore geology. When he wasn’t seasick, he read Lyell’s Principle’s of Geology. He also found fossils in the Andes showing that a possible earthquake event happened.

Later, Darwin became interested in the different species of birds on the Galápagos Islands such as the mockingbird and the finch. While observing the mockingbirds, he noticed that they were unique to each other in different environments.

There were many organisms that showed adaptations. Adaptations are traits that are given to offspring by one or both parents that help that organism survive and pass on its genes in certain environments (Reece 440).

When Darwin observed finches, he found that different finches eat different things and have unique beaks to suit their needs. How did these animals become different from each other? Darwin’s explanation was natural selection.

Natural selection is process in which organisms that are a better suited for their environment survive and reproduce (Reece 441). A parent who has a trait that helps them live is more likely to pass on that trait to its offspring allowing that offspring to do the same. For natural selection to work, reproduction is at its highest.

A great example of natural selection is Darwin’s finches.

• There’s the cactus-eater (example: Geospiza scandens). The cactus-eater is able to eat cacti with its long sharp beak.

• There’s the insect-eater (example: Certhidea olivacea). The insect-eater with its small pointy beak can smash insects and eat them.

• There’s also the seed-eater (example: Geospiza magnirostris). The seed-eater has a very large stout beak to crush seeds with.

These different birds deal with different environments. If the cactus-eater was somehow transported to the insect-eater’s environment, they wouldn’t survive. The cactus-eater doesn’t have the right beak to eat insects.

In The Origin of the Species Darwin called evolution “descent with modification” meaning organisms become different species. In his book, he never used the word “evolution.” He believed that every organism descended from one life form (Reece 441).

Darwin perceived life as a tree. Different branches and twigs are different species.

Darwin’s Tree of Life. [Source https://www.age-of-the-sage.org/evolution/charles_darwin/tree_of_life.html]

This way of looking at different forms of life is still used.

Let’s Recap

Natural selection involves an inheritable trait or adaptation that an organism uses to survive and give to its offspring. After long time, organisms living in a certain area will become better suited for that area. When or if the habitat changes, life may also adapt bridging a way for a new species.

https://slideplayer.com/slide/9367977/
http://www.basfeijen.nl/evolution/darwinsfinches.htm
http://theoatmeal.com/blog/jibbers_crabst