Which of Darwin's ideas had the strongest connection to Thomas Malthus's essay on human population growth? a. descent with modification b. that the ancestors of the Galápagos finches had come from the South American mainlandc. variation among individuals in a population d. struggle for existencee. the ability of related species to be conceptualized in "tree thinking"

d. struggle for existencee.

Explanation:

Malthus's essay main theme was that - population size will always undergo an exponential growth; and as this continues this supersedes available food supply growth. The negative effects of this on the population is struggle for survival for limited food available leading to hunger, famine and death.

The word ' struggle' for survival in Malthus essay intrigued Darwin's, and this formed the basis of his theory.

Darwin discerned that some organisms within the population will be able to struggle and survive and therefore withstand the selective pressure of limited food supply, while those without ability to struggle will die of hunger, and diseases. He concluded that, the ability to struggle for existence by some members of the population, was due to some inheritable characteristics which they must have inherited from their previous generation. While those that could not withstand the selective pressure, died of hunger.

Basically, variation (not mentioned by Darwin) was the factor that ensure struggle for existence for the survival of the fittest, and nature will select the fittest compare to those without variation. The organisms without ability to struggle will die, and the new population with ability to struggle to survive will evolved. - this is the theory of evolution, this is Dawin's theory of natural selection.