Other Chapters' Lyrics:
Earth Science 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 -:- Life Science 1 - 2 - 3 - 3b - 4 - 4b - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12 -:- Physical Science 3
Other Chapters' Notes:
Earth Science 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 -:- Life Science 1 - 2 - 3 - 3b - 4 - 4b - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12 -:- Physical Science 3
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Life Science Chapter 7 - Summary Notes
What is evolution and how do we track it?
- An adaptation is a characteristic that helps an organism survive and reproduce.
- Species often share similar adaptations. A species is a group of organisms that can mate with each other to produce fertile offspring.
- Populations accumulate inherited changes over time through evolution.
- Scientists use fossils to track these changes. Fossils buried deeper are presumed to be older.
- The fossil record is incomplete because oxygen exposure causes many fossils to decay. Still, there are things to be learned from the fossils we do have.
Shared traits as an indicator of evolution:
- Vestigial structures are remnants of structures that were once useful. For example, whales have incomplete hind limb bones in their body. Whales may have descended from land animals that eventually adapted to water.
- The DNA of some species is more similar to the DNA of others. Scientists think that species with more similar DNA are closer relatives on the evolutionary tree.
- Similar body parts may indicate that species have a common ancestor. For example, the bones of a human arm roughly resemble the bones of a cat’s leg, which could mean we have evolved from the same species.
Natural selection drives evolution:
- After noticing differences between individuals of a species, Charles Darwin proposed the concept of natural selection.
- Natural constraints don’t allow for all individuals to survive. The ones with adaptable traits tend to reproduce, producing more offspring with those traits. As traits keep passing down, species change over generations.
- Individuals within the same species can adapt in different ways, and this can happen so much that speciation occurs. This is when a species becomes two species that can no longer interbreed.