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Transcript of Evoultion
Naturalist on the British ship HMS Beagle
Was amazed by the diversity or Variety of the living things he saw.
Was puzzled by bones of animals that had died long ago. What happened to them?
Darwin observed the greatest diversity here
Noticed many organisms on the island were very similar to organisms on the mainland of South America
HOWEVER there were important differences
Example: Iguanas on the mainland have smaller claws then those on the island
Darwin inferred that many of the animals came to the island from the mainland
They could have been blown out to sea during a storm or floated on drift wood
When the animals reached the island, they reproduced and eventually the offspring became different from those on the mainland
There were also differences among the animals
that lived on the different islands of the Galapagos
Example: Tortoises on one island had dome shaped shells while on another island the tortoises had saddle shaped shells.
Finches also had different sized and shaped beaks on different islands
They were each suited for the life they led: if they ate insects they had sharp needle-like beaks.
If they ate seeds they had strong, wide beaks. This is an example of Adaptation
adaptation- a trait that helps an organism survive and reproduce
Darwin thought that species gradually changed over many generations and became better adapted to their new conditions. This idea is referred to as the theory of evolution
Evolution- The gradual change in a species over time
The Origins Of Species
Book Darwin Published to explain how evolution occurs
Explained that evolution occurs through natural selection
Natural Selection is the process by which individuals that are better adapted to the environment are more likely to survive and reproduce.
Role of Genes
Mutations can often show up in an organism's genes. Mutations lead to variations.
Variation- any difference between individuals of the same species
Example: speed in which sea turtles swim
can form when a group of individuals remains separated from the rest of its species long enough to evolve and show different traits than the original species. This is called geographic isolation.
Hundreds of millions of years ago all of earth's landmasses were connected in one supercontinent called PANGAEA
Pangaea gradually split apart in continental drift. As the continents drifted apart the species became isolated