CHANGES OVER TIME. Darwin’s Theory Evidence of Evolution The Fossil Record. Unit Preview. Darwin’s Theory. What important observations did Darwin make on his voyage? What hypothesis did Darwin make to explain the differences between similar species?
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Scientific Theory -
Individuals that are better adapted to their environment are more likely to survive.
A well-tested concept that explains a wide range of observations.
A group of similar organisms that can mate with each other and produce offspring.
Any difference between individuals of the same species.Key Terms
Darwin was puzzled by some of the fossils he observed.
He saw fossil bones of animals that had died long ago but yet resembled the bones of organisms alive in Darwin’s time.FOSSILS
He compared Galapagos organisms to organisms that lived elsewhere.
He also compared organisms on different islands in the Galapagos group.
He tried to make connections using the similarities and differences he observed.Galapagos Organisms
Grip slippery rocks
Feed on seaweed
The iguanas on the mainland had smaller claws.
Darwin was able to identify which island an organism came from just by looking at it.Comparisons Among the Islands
Beak shape was based on their diet.
Narrow, needle-like beaks = insects
Strong, wide beaks = seedsGALAPAGOS FINCHES
Evolution occurs by means of NATURAL SELECTION.Natural Selection
GenesFactors Affecting the Process of Natural Selection
A large number of offspring creates competition for resources.OVERPRODUCTION
Variations are linked to environmental conditions.VARIATIONS
Searching for food
Individuals who are better adapted survive and reproduce.
Helpful variations may gradually accumulate in a species, while unfavorable ones may disappear.SELECTION
The environmental change can gradually lead to selection.
The Galapagos Islands are a prime example of how the environment can lead to the evolution of a species by natural selection.ENVIRONMENTAL CHANGE
Natural selection would not occur because all the individuals would have an equal chance of surviving and reproducing.
Variations can result from mutation and the shuffling of alleles during meiosis.
Genes are passed from parents to offspring.GENES
. . . Survival of the Fittest!