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External factors include physical and chemical signals. Growth factors are proteins that stimulate cell division. – Most mammal cells form a single layer in a culture dish and stop dividing once they touch other cells.
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From Google
Answer: they allow air to enter lungs and also permits air into the body
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Answer:
Ecosystem diversity is a type of biodiversity. It is the variation in the ecosystems found in a region or the variation in ecosystems over the whole planet. Biodiversity is important because it clears out our water, changes out climate, and provides us with food.
Explanation:
Farming meant that people did not need to travel to find food.( nomadic lifestyles became scarce) Instead, they began to live in settled communities,or villages and grew crops or raised animals on nearby land. They built stronger, more permanent homes and surrounded their settlements with walls to protect themselves.
