1. Explain why any one species cannot live everywhere. Any species cannot live everywhere because this would effect the natural balance. Also one species cannot adapt to all the different environments of our planet. For example a marine creature can only live underwater and cannot live on ground. 2. Explain how the activities of some species can lead to: b) a decrease in the population size of another species. Some species act as population controllers of other species. There must be a 'balance' between the two and this is important to a healthy landscape. The decrease in the population is caused by the food