Which characteristic is common to all hermaphrodites?

Hermaphrodites are organisms that possess both male and female reproductive organs, allowing them to have the potential for both reproductive roles. The characteristic that they can change their reproductive roles in response to environmental factors is fundamental to many hermaphroditic species. This adaptability can be advantageous in various situations, such as when the population density alters the availability of partners, thus maximizing reproductive success.

For instance, if a hermaphrodite finds itself in an environment with a low number of potential mates, it may switch roles to ensure that reproduction occurs. This flexibility enhances genetic diversity and survival chances for the species.

The other options do not accurately describe hermaphrodites. While some hermaphrodites can reproduce asexually, many have the ability to reproduce sexually as well. Not all hermaphrodites exclusively utilize external fertilization; in fact, some can also reproduce via internal fertilization. Lastly, hermaphrodites are capable of reaching sexual maturity; this characteristic is essential for their role in reproduction and their life cycle. Therefore, the ability to change reproductive roles in response to environmental conditions is a key characteristic that defines hermaphrodites.