Final answer:
The concept from Darwin's theory that relates to organisms producing more offspring than can survive, leading to competition and variation, is known as Overproduction. It is a key element of the principle of natural selection.
Step-by-step explanation:
The part of Darwin's theory that describes the concept where animals and plants tend to produce more offspring than can survive is known as Overproduction. This principle is a cornerstone of the theory of natural selection, which is further supported by the principles of variation in traits and competition for limited resources. Charles Darwin and Alfred Russel Wallace, both discoverers of natural selection, understood these concepts partly from reading Thomas Malthus' essay about human population growth, which suggested that not all individuals in a population will survive and reproduce due to limited resources. Because organisms vary in their traits, and because these traits can be inherited, offspring with traits that confer a survival advantage in their particular environment are more likely to survive and reproduce, thus passing on these advantageous traits to their offspring. Over generations, this process can lead to the evolution of populations, with traits that are better adapted to the local environment becoming more common.