Assume that an organism has not reached sexual maturity. What life process will the organism divert the majority of its energy toward? (A) Reproduction, (B) growth, (C) excretion, or (D) parental care.
The question asks us to identify a life process, which is an action that is essential for the survival of an individual or species. There are seven major life processes: movement, respiration, sensitivity to surroundings, growth, reproduction, excretion of waste products, and nutrition. We can remember these life processes using the mnemonic device Mrs. Gren.
Nearly all of the life processes are essential for the survival of an individual. For example, all living things must obtain nutrition and undergo cellular respiration to convert this nutrition into energy for growth. Reproduction is a unique life process because an individual does not need to reproduce to survive. But what do you think would happen if none of the individuals in a population reproduced? As the adults died off, there would be no offspring to replace them and the population would not survive. If this lack of reproduction continued on a larger scale, that is, in multiple populations of the same species, it would eventually lead to extinction of the entire species. So, although reproduction is not essential for survival of an individual, it is essential for survival of a species.
Now let’s return to our question. We’re told to assume that the organism has not reached sexual maturity, which is the physiological capability to produce offspring. The time it takes to reach sexual maturity varies widely among species, from just a few weeks in certain types of killifish to 150 years in the Greenland shark. In any case, an organism that has not reached sexual maturity cannot reproduce. So it would not divert any of its energy toward reproduction. Parental care is not an essential life process, and it can only occur when an individual has offspring to care for. So we can rule out this answer choice as well.
Before reaching sexual maturity, an organism will prioritize its development and survival. And both growth and excretion are absolutely essential during this phase. But the question asks us where the organism would divert the majority of its energy. And growth nearly always requires more energy than excretion. Therefore, an organism that has not yet reached sexual maturity will divert the majority of its energy towards growth.