Complex sentence: T.H. Huxley, commonly known as Darwin's Bulldog, clearly explains the struggle for existence in terms of natural selection: the struggle for existence is inferred based on the fact that populations would grow geometrically if unchecked but populations tend to stay constant in number over time.
Split into simpler sentences: T.H. Huxley, commonly known as Darwin's Bulldog, clearly explains the struggle for existence in terms of natural selection. Huxley explains that the struggle for existence is concluded based on the fact that populations grow geometrically if unchecked but populations tend to stay constant in number over time.