How does parthenogenesis relate to reproduction?

Answer 1

Parthenogenesis is a process whereby a single egg can develop without the presence of biologic material (sperm) from a male. In some lower animals parthenogenesis can lead to reproduction naturally, for example, it is a common form of reproduction in flies, ants, lizards, snakes, fish, birds, reptiles, amphibians, honeybees, and crayfish. Eutherians (mammals with a placenta) are not capable of this form of reproduction; therefore parthenogenesis is not known to occur naturally in primates or most other higher order animals. The advantages of parthenogenetic reproduction are that without sex, parthenogenesis takes less energy and allows for more rapid reproduction in the short term. This is great for insects that may want to increase their numbers quickly to inhabit a new territory. In addition, it allows reproduction to occur in some animals when sexual reproduction is impossible; for example, if a female were isolated and unable to find a male with whom to mate. Finally, if a species is already well adapted to its environment, it may not pay to expose the species to the genetic variation brought by sexual reproduction. However, on the flip side, because only one individual's genes are passed on to the offspring, parthenogenesis limits genetic diversity and without diversity, genetic mutations can amplify within a species. Although mammals do not reproduce using parthenogenesis, parthenogenesis can be used to cause an unfertilized human egg to form a ball of cells called a blastocyst from which human stem cell lines can be created. These stem cell lines (called parthenogenetic stem cell lines) have been shown in published research to have the same capacity as an embryonic stem cell line to create, through differentiation, the basic human tissues that lead to all cells in the human body. In addition, researchers have shown that specific human cells created from parthenogenetic stem cell lines, such as liver-like cells, retinal pigment cells, nerve cells or beating heart-like cells may be useful for research and for therapies based on cell implantation. However, the parthenogenetic blastocyst, even if implanted back into the womb of the donor, would not produce a viable fetus so nothing that could become a viable human life is ever destroyed.