Final answer:
Among the listed options, agave plants (a) are semelparous, which means they reproduce only once before they die, contrary to dogs, bears, humans, and oak trees that can reproduce multiple times (iteroparous).
Step-by-step explanation:
The organism that is semelparous among the options given is (a) agave plants. Semelparity, also known as big bang reproduction, is a life history strategy characterized by a single reproductive episode before death. In contrast, iteroparity refers to multiple reproductive cycles over the course of an organism's life.
Unlike dogs, bears, humans, and oak trees, which can produce offspring multiple times in their lifetimes; agave plants typically flower once, produce seeds, and then die. This strategy is effective in certain environments where the chance of survival for offspring may be higher during certain conditions, leading to a synchronization of reproductive efforts for maximum impact.
Semelparity is not exclusive to agave plants; many other organisms, including some insects, fish (like salmon), and annual plants, also exhibit this reproductive strategy. It's important to note that semelparity and iteroparity are evolved life-history traits that represent adaptations to specific environmental conditions.