Presentation on theme: "A Scientific Explanation of How All Living Things Came to Be."— Presentation transcript:
A Scientific Explanation of How All Living Things Came to Be
The Theory of Evolution is the Scientific explanation for how all of Earth’s living organisms came to be, and how we grew to be so different. This modern theory began around 150 years ago when a British scientist named Charles Darwin made an amazing discovery that revealed how creatures adapt to their environments. Since that time the theory has grown in complexity and strength.
Before the Theory of Darwin different cultures had many different ways for explaining the world and all the creatures in it. Many believed that the creatures currently on the planet were the only creatures that had ever been on the planet. However, people began to come across the remains of bizarre creatures that did not exist anywhere on the planet. What they had found was the remains of creatures that used to live on the planet. That revelation changed our world view and eventually opened up the way for Darwin’s ideas.
Jean Léopold Nicolas Frédéric Cuvier, known as Georges Cuvier, was a French naturalist and zoologist. Often viewed as the man who brought vertebrate paleontology into existence Cuvier made a ground breaking discovery while exploring the remains of a mammoth: the mammoth was not a modern elephant! In the 1790s he began comparing the remains of mammoths to those of living elephants. He soon discovered that not only were the mammoths very distinct from the living elephants on the planet but that the mammoth was an extinct species!! Before then people simply thought they were a hairy version of the living elephants.
Mary Anning was a young English girl who would become one of histories most famous fossil hunters. Around 1810, she discovered the first complete specimen of an extinct ichthyosaur (a marine reptile with a sharklike body). Discoveries like this one, and others made by her and others, would confirm Cuvier’s idea that some animals had become extinct. However, no one had an accurate Scientific sense of the Earth’s age or from when in our past these creatures had died out.
In the 1800s, geologists began to realize that the layers in the Earth’s rocks were actually a record of time; particularly sedimentary rock. As new layers of sediment, lava, etc. were deposited on top of older layers, a stack was created. People began to realized that in some regions the layered rock record was many miles thick. More importantly, certain fossils only ever showed up in certain layers. So collections of fossils were specific to time periods. Lastly, the further back in time you went, the more alien looking the fossils became. Recent rock layers had creatures that resembled modern animals but ancient layers had very strange, unique looking specimens.
Charles Darwin was a young English naturalist who volunteered to serve on the Beagle; a ship on a map making mission around the globe. He was to serve as the captain’s company at dinner and to collect plant and animals species from the various places they stopped. While at the Galapagos Islands, he collected tortoises and birds. Later, when he was back in England, a bird expert noticed something remarkable about some of the birds from this region. Though they all looked different from one another, they were in fact all finches.
He began to explore how did one island’s finches become so different from one island’s finches. Darwin formed a theory that they were all descended from a species of mainland finches that had made their way to the islands. However, different islands had different food sources available for the finches. Therefore, in order to eat, the finches somehow developed beaks suited to the food sources available. But how? How could one species turn into several new species?
A species is a group of living things that can reproduce (create new life) with one another but not with other life-forms. E.g. Cobras can breed with other cobras, giraffes with giraffes, but cobras and giraffes could not breed with each other. In fact, just because a cobra is a snake does not mean it can breed with all other snakes. So how can a new species be created. Well, that was the easy part to discover as humans have been creating new species for thousands of years.
People have been creating new species of animals for thousands of years. The vast variety of dog breeds, cat breeds and horse breeds are amazing examples of this. Darwin had a barnyard hobby; he bred pigeons. This was quite popular in his day. People would find pigeons with certain traits (e.g. fluffy feathered feet) and breed them with other pigeons with that trait. Some of the pigeons’ offspring would be normal, but some would have fluffier feet. Repeat this process for a few generations and you end up with pigeons with ridiculously feathered feet.
So if people could change a species in a few generations, could this occur naturally. Darwin began to examine the creatures of the world and came to the conclusion that it could. Over a time a species could adapt to survive. He refined his thoughts into what would become the Theory of Natural Selection. Fancy Pigeons
1) All creatures struggle to survive and reproduce, but many fail. 2) Creatures that happen to be born with an advantageous trait are the most likely to reproduce. 3) Parents can pass on their advantageous traits to their offspring. 4) From there, all it takes is time. **Vice versa – creatures born with disadvantageous traits are less likely to survive and reproduce, so their traits disappear.
Darwin knew his ideas would be controversial and had difficulties with them himself. For years he kept his ideas to himself. However, another English naturalist called Alfred Wallace made his own discoveries and formed his own theory similar to Darwin’s theory of natural selection. When they compared notes and realized that they had both independently come to the same conclusion they decided to share their idea. In 1858 they presented their idea together to the Scientific society.