22-year-old medical student Joined the HMS Beagle as the ship’s naturalist - A naturalist was a scientist that studied the world, specifically the new plants and animals. The world was still a very new place with many undiscovered organisms. Every exploratory ship (like the HMS Beagle) took a naturalist along to study and discover new species.

A species is a group of similar organisms that can mate with each other and produce fertile offspring. This is a tigon. His mom was a lion and his dad was a tiger. Tigons are not a new species because they cannot produce fertile offspring. These are all known species. Write down 5 that you can identify!

Darwin’s most famous observations came from the Galapagos Islands (4 years into the voyage)

 Here is an up-close view of the Galapagos Islands  This also shows how the HMS Beagle sailed around the islands, constantly stopping and sending out survey boats to discover new species, people, and lands.

Galapagos Iguana Mainland Iguana  Darwin noticed that the iguanas on the Galapagos Islands had claws that were larger and more dull, which helped them keep hold of the slippery rocks they stood on as they ate seaweed  Mainland iguanas (those found on the main continent of South America) had skinnier, sharper claws that allowed them to climb trees to eat leaves

 Darwin also made observations about the finches found on the different Islands that make up the Galapagos. He noticed their beaks differed based on what they ate. For example, finches that ate insects had more narrow, needle-like beaks. Finches that ate seeds had more strong and wide beaks.

 The finches’ beaks are an example of an adaptation.  Adaptation – a trait that helps an organism survive and reproduce  This is a moth that blends well with tree bark. For his family members that are a slightly lighter or darker shade, they are more likely to be eaten by hungry birds because they would stand out more than this moth.

Darwin eventually returned to England and thought on his ideas for the next 20 years. He reasoned that when a species faces a new or different condition, they gradually change from generation to generation to be better adapted to the new environment. For example, that moth we just looked at… The darker moths blended in better because there was a lot of soot in the air that stuck on the trees and made them darker. However, restrictions were then put in place that got rid of a lot of soot in the air. The trees then started getting lighter, so the lighter moths then started doing better, and the darker moths started being eaten by birds.

Natural selection – process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species

The short-necked giraffes will not get much food, and will die. Because of this, they will not pass on their short-necked alleles to any offspring. Eventually, all shorter- necked giraffes will die, and all new giraffes being born will have long-necked alleles.

All long-necked giraffes are left. This is the same exact thing that happened with the happy bears and sad bears in the Teddy Graham Lab! The happy bears had the favorable trait, so they survived and had offspring much more often than sad bears. Eventually, all the sad bears would disappear, and only happy bears would have been left.

Overproduction (1) Variations (2) Competition (3) Environmental Change (4)

 Most organisms create many more offspring than can survive. There is not enough food, water, etc. Overproducing provides the whole species a better chance of surviving by having many offspring with many different types of traits.  The environment will naturally select for the best traits, and those will survive.  Variations are any difference in individuals among a species. For example, color. In the moths from earlier, their color was a variation that benefitted them at different times. Below is several variations of rabbit fur color. If these were living in the tundra where there is snow a lot, the lighter- colored rabbits would benefit and survive longer. If they were living in a lava field, the darker-color rabbits would survive better. Either way, the ones that survive pass on their fur color alleles to their offspring, so the population would begin to have more and more of that color fur.

 Most resources for a species are limited. There is usually not enough food, water, and shelter for all offspring to survive. Individuals are constantly competing indirectly for these resources.  A change in the environment can lead to different variations surviving. For example, when we looked at the moths… The soot in the air made the trees darker, which favored the dark moths. When the government put restrictions on the amount of soot that could be in the air, the tree trunks got lighter again. This was an environmental change. It cause the lighter-colored moths to be able to survive better and produce more offspring.

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