A hermaphrodite is an organism with both male and female genitalia. In sexually reproducing organisms, males have organs that produce male gametes, usually sperm. Females have different sexual organs that produce female gametes, usually called eggs. In sexually dimorphic organisms, each organism only has type of reproductive organs, and the population is divided into genders. Sometimes the organisms are divided almost equally. In these cases, individuals must compete for mates. Sometimes the genders pair off equally, one male for one female. Other times, one male or female will breed with a large group of the other gender.
Hermaphrodites tend to be solitary animals, although exceptions exist. Being a hermaphrodite is thought to increase the chances of solitary organisms reproducing, because they can both give and receive gametes. This allows them to both share their DNA, while at the same time having the chance to develop an offspring of their own. Young developing in two different places also decreased the chance that a random event will wipe out both young. When you live as a solitary animal and mating opportunities are scarce, this is an important advantage for hermaphrodite organisms.
Causes of Normally Dimorphic Hermaphrodites
In sexually dimorphic organisms, a hermaphrodite may arise because of variations in the genetic code. In humans, hermaphrodites are caused by a variety of genetic conditions. In one form, a hermaphrodite or intersex person is created when two fertilized eggs fuse together, giving the zygote two X chromosomes and one Y chromosome. Other cases of hermaphrodites are caused by the SRY gene, the gene responsible for testosterone and male genitals, being transferred to the X chromosome during meiosis, resulting in both male and female genitals.
Examples of Hermaphrodite
In clownfish society, the only two individuals that get to breed are the two largest individuals. Although all clownfish are born with non-functioning genitals, the largest clownfish undergoes a change when it becomes the largest fish, and ovaries develop and start releasing eggs. This female needs a male to reproduce with, and the second largest fish develops testis that produce sperm. The couple continues to reproduce until one of them dies, in which case they are replaced by the next largest individuals. If the female dies, the male converts from female to male genitalia. This is known as sequential hermaphrodism. When the organism starts off as male, they are called protandrous hermaphrodites or “first male” hermaphrodites. When they start as female, they are known as protogynous hermaphrodites, or “first female” hermaphrodites.
A hermaphrodite that can be found in your own backyard is the earthworm. Earthworms spend their days deep beneath the soil, burrowing in random directions and aerating the soil. Two earthworms could be only a short distance apart, and never come into contact. Because of this isolated lifestyle, it is important for the worms to be able to reproduce successfully when they meet. The earthworms are hermaphrodites and have both male and female genitalia. When they copulate, both organism give a gamete and receive a gamete. When they separate, each earthworm wraps its eggs in a cocoon and deposits them in a safe location. This gives the worms two separate populations of offspring that have different chances of surviving. An added benefit of being a hermaphrodite is that if a worm never finds a mate, it can fertilize its own eggs and reproduce that way. Many hermaphrodites experience this benefit.
Some plants are hermaphrodites. In their reproductive organs, flowers, there are both male and female reproductive systems. The pollen or male gamete is released from a stamen. The female part, the stigmata, is a long tube that leads to ovules containing eggs. The pollen must make its way from the stamen to the stigma. Sometimes this happens on the same plant, and sometimes bees and other pollinating insects carry the pollen from one plant to other. Much like the earthworm, plants benefit from being able to fertilize their own eggs and being able to reproduce sexually to increase their variety. Even so, plants always need pollinators, or at least a strong wind, to move the pollen to the stigma. Other plants are not hermaphrodites and produce only one type of flower. It all depends on how the plant species evolved.