Sexual reproduction cells. Or just sex cells
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Animal Respiration Every cell in an animal requires oxygen to perform cellular respiration. Cellular respiration is the process by which animals take in oxygen and exchange it for carbon dioxide and water as waste products.
Answer:
A closed system is a physical system that does not allow transfer of matter in or out of the system, though, in different contexts, such as physics, chemistry or engineering, the transfer of energy is or is not allowed.
After the Big Bang happened, the universe is constantly expanding. The Universe has expanded for around 13.7 billion years. The further a galaxy is, the faster it would move away from Earth. This principle is called the conservation of momentum.