Explain how oxygen in the atmosphere is responsible for the formation of other elements.

Oxygen is essential to enabling many of the Earths life forms to survive -- without access to oxygen, humans cant live for more than a few minutes. The air that enters human lungs contains about 21 percent oxygen. The process responsible for producing most of the Earths oxygen is known as photosynthesis. In this process, plants and certain other organisms convert sunlight into oxygen and other products.

Explanation:

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.

he forelimbs below belong to four species that descended in a direct line from the ancestral mammal shown above. of the four descendants shown, which species most likely appeared earliest in evolutionary history?