Answer:
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Answer:
Volcanoes, geysers, and hot springs all provide clues about Earth's interior. They also show one of the ways that Earth's layers interact with each other.
Explanation:
There are three sources of genetic variation: mutation, gene flow, and sexual reproduction. A mutation is simply a change in the DNA.
Answer: The immune system
Explanation:
The immune system is a complex network of proteins and cells that defends the body against infection or any invasion. The human defense system in the body is actually made up of entire organs and vessel systems like the lymph vessels. The immune system is made up of organs that control the production and maturation of certain defense cells.
Initially, all living things are subjected to attack from disease causing agents. Even bacteria, so small that more than a million could fit on the head of a pin, have systems to defend against infection by viruses. This kind of protection gets more sophisticated as organisms become more complex.
