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Section 7-1
Darwin’s Voyage
• A naturalist that traveled on the HMS Beagle
in 1831
• Developed the theory of evolution by natural
Darwin’s Observation
• Diversity
– Noticed a wide variety of organisms, many of which
hadn’t been discovered
• Species – a group of organisms that can mate and produce
fertile offspring
• Fossils
– Noticed the remains of species no longer in existence
– Wondered why they looked similar to those existing now
• Example: Fossils of sloths much bigger than current sloths
Galapagos Islands
• Small group of volcanic islands off South
– Isolated from the mainland
• Noticed that organisms on the islands had
similar traits to those on mainland
– Traits seemed to match environment
– Iguanas on mainland were green (match jungle)
and grey on islands (match rocks)
• A trait that helps an organism survive and
– Example: Long necks allow giraffes to get food
from tall trees
• Darwin’s Conclusion
– Organisms gradually change over many
generations to match the environment
• Selective Breeding is Evolution
– Nature “selects” organisms with desired traits to
survive and reproduce
– Called Natural Selection
Natural Selection
• Includes three factors that control evolution
– Overproduction – making more offspring than can
possibly survive
• Insects lay thousands of eggs so only the strongest make it
– Variations – differences among members of the same
• Peppered moths come in black and white
– Competition – members of a species compete for living
space and food