Answer:
Scientists estimate that at least 99.9 percent of all species of plants and animals that ever lived are now extinct.
Explanation:
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Answer:
Disease and Famine
Explanation:
If there is a disease that affects a type of plant, having other types of crops to rely on could save one from starvation. Also, only planting one crop in an area can change the pH and nitrogen levels in negative ways, so that eventually no plants can grow there. Not to mention the obvious balanced diet needed for a healthy body.