Final Answer:
Thomas Malthus' use of mathematical description of the changes in human population size explained the principle of population growth in relation to available resources.
Step-by-step explanation:
Thomas Malthus' use of mathematical description: Malthus employed mathematical models to illustrate trends in human population dynamics.
Changes in human population size: Malthus aimed to elucidate how the size of the human population undergoes fluctuations over time.
Explained the principle of population growth: Malthus's mathematical analysis served to explicate the principle that population tends to grow exponentially, posing challenges when resources are limited.