Now listen to part of the lecture from an environmental science class.
Okay, so an example of this is when chickens are used to prepare a field for planting. Farmers who do this have a special kind of little house that they keep their chickens in. This little house has four walls and a roof but it doesn't have any floor. And it has wheels attached to it so it can easily be moved from one location to another. So farmers move this little house to a field where something is going to be planted. Say, bean plants. And then the chickens are placed inside the house, now remember there is no floor in this house and what the chickens do is they walk around inside the house and peck up the soil and eat any weeds or wild plants that they find. And then when the chickens are done eating the weeds in that location, the farmers move the house to the next section of the field. And again the chickens peck up the soil and eat the weeds. So the chickens get to eat a lot of weeds which are good for them. Now this activity is also good for the bean plants that'll be growing in the field, because when the chickens eat the weeds they're improving the quality of the soil. Thanks to the chickens when the bean plants start to grow there won't be any weeds there to compete with them for crucial resources, like sunlight and water.