There are more than 400,000 types of plants, and they include the tallest, heaviest, and oldest living things on Earth. Together, they make up the plant kingdom, one of the five kingdoms of living things. Like animals, plants need energy to survive and to grow, but they get it from sunlight instead of from food. Life on Earth depends on plants. All animals eat plants or plant-eaters. As a by-product of making their own food, plants release oxygen—the gas that all animals need to breathe.