Answer:
The mass number of an atom is its total number of protons and neutrons. Atoms of different elements usually have different mass numbers , but they can be the same. For example, the mass number of argon atoms and calcium atoms can both be 40.
Explanation:
At the bottom is the common phospholipid ,phosphatidylcholine.lipids are a group of naturally occurring molecules the include fats ,waxes ,sterols ,fat-soluble vitamins.
Answer:
faced a struggle for survival
Explanation:
The woolly mammoths became extinct, unlike the other species, because the woolly mammoths faced a struggle for survival due to changing of environmental conditions. Global warming is the main cause of extinction of woolly mammoth which destroy their habitats about 10,500 years ago. The environmental conditions are not favourable for them so they faced struggle for survival which causes extinction of woolly mammoth.
