We’ve all heard about the naturalist, 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 fossils and the layers of rock that cover them (strata). So he had context before he set foot on the HMS Beagle.
After dropping out of medical school to go to Cambridge, Darwin met Captain Robert Fitzroy of the HMS Beagle.
Fitzroy wanted to document the shorelines of South America and asked Darwin if he wanted to come. He said yes.
In December 1831, they set off on their journey. For most of the trip, Darwin observed nature in South America. While observing, 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 Principles of Geology. He 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. According to Campbell Biology, adaptations, in certain environments, are traits given to an offspring by one or both parents that help that organism survive and pass on its genes (2013, 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.
In Campbell Biology, natural selection is the system in which organisms that are better suited for their environment (as opposed to organisms that aren’t) 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 (examples provided by Campbell’s Biology: Reece 467).
These different birds deal with different environments. If the cactus-eater was somehow transported to the insect-eaters 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 (2013, Reece, 441).
With branches and twigs representing different species, Darwin perceived life as a tree.
This way of looking at different forms of life is still used.
Natural selection involves an inheritable trait or adaptation that an organism uses to survive and give to its offspring. After a long time, a species living in a certain area will become better suited for that environment. When or if the habitat changes, said species may also adapt bridging a way for a new species (2013, Reece, 444).
Natural selection is not “survival of the fittest” in which an individual organism is physically apt. Natural selection involves the survival of an entire species in its environment.
Reece, Jane B. Urry, Lisa A. Cain, Michael L. Minorsky, Peter V. Jackson, Robert B (2013). Campbell Biology. (10th ed.) Boston, MA: Pearson.