Final answer:
Darwin understood from Malthus that populations could grow exponentially, but this growth was limited by resource availability, leading to a struggle for existence where only some individuals survive and reproduce.
Step-by-step explanation:
Charles Darwin obtained important insights from reading Thomas Robert Malthus's An Essay on the Principle of Population, which influenced his theory of natural selection. The key idea Darwin got from Malthus was that populations grow exponentially when unchecked, but their resources do not, leading to a 'struggle for existence.' Darwin applied this understanding to his concept of natural selection, concluding that in nature, organisms produce more offspring than can survive in their environment. This overproduction results in competition for resources, where only individuals with favorable inherited traits are likely to survive and reproduce, passing those traits on to the next generation, a process he termed 'descent with modification.' Thus, the correct answer is that from Malthus's work, Darwin understood that more individuals of a population are born than survive to reproduce.