Famine- High population means more mouths to feed
Disease- Diseases usually spread more quickly with people who live closer( as it can just move from one person to the other)
War- People like to fight for land, resources, money, etc. And having more of those things mean they are more able to support families, communities, and more.
(Hope this helps a little)
Answer:
Cell is the basic , functional unit of life
An atom is the smallest unit of ordinary matter that forms a chemical element .
Ozone protects the Earth from harmful UV rays from the Sun.
