The air that we breathe is mostly made up of nitrogen (78%). 21% is oxygen which is needed for animals and humans in respiration and 0.03% is carbon dioxide which is needed for plants to make energy in a process called photosynthesis. The bit that is left is made up of rare gases like helium and argon and methane.
Answer:
Physicals changes, the way your skin wrinkles. Basically all the stuff you body goes through over your life time
Explanation:
Before the discovery of DNA strands, scientists thought that genetic material was stored within protein.
Answer:
secretion
Explanation:
Epithelial cells are usually cells located or found outside the body, skin, urinary tract, vessels, cavities, and organs of the body, and have special modifications of their surfaces which depends upon the specific roles they perform and where they are found. However, many types of epithelial cells perform a common function of secretion. Epithelial cells are closely packed together.
Because a jet engine needs air to propel the plane, and there is no air in space so there is no lift for the plane keep flying.
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