Vidence of common descent<span> of </span>living organisms<span> has been discovered by scientists researching in a variety of disciplines over many decades, demonstrating the </span>common descent<span> of all </span>life on Earth<span> developing from a </span>last universal ancestor<span>. This evidence constructs the theoretical framework on which evolutionary theory rests, demonstrates that </span>evolution<span> does occur, and is able to show the natural processes that led to the emergence of Earth's </span>biodiversity<span>. Additionally, this evidence supports the </span>modern evolutionary synthesis<span>—the current </span>scientific theory<span> that explains how and why life changes over time. Evolutionary biologists document evidence of common descent by developing testable predictions, testing hypotheses, and constructing theories that illustrate and describe its causes. Hope you get it!</span>
Answer: The different layers are a result of lighter parts (such as the continental crust) settling at the surface level and heavier parts (such as iron and nickel in the core) settling in the middle. The layers separate by density, otherwise known as compositional layering. The earth did not always have these layers, as it had to undergo cooling to form some of them (like the continental crust).
In order for gas to leave a planet it needs to be hot enough and to overcome the planets gravity. The outer planets are colder and are very big compared to earth.
