True all because of the food chain. For example when predators get killed then the predators prey overpopulates and causes the prey to eat too much of the plants. Causing us to loose food supplies and oxygen.
I'm thinking true heres why lets say you have a bird and the bird eats worms.. and all the worms in the world are gone the bird will die and what ever animal ate that bird will die and what ever animal ate that bird will die and so on
