Many organisms can reproduce sexually as well as asexually. Aphids, slime molds, sea anemones, some species of starfish
and many plants are examples. When environmental factors are favorable,
asexual reproduction is employed to exploit suitable conditions for
survival such as an abundant food supply, adequate shelter, favorable
climate, disease, optimum pH or a proper mix of other lifestyle
requirements. Populations of these organisms increase exponentially via
asexual reproductive strategies to take full advantage of the rich
supply resources.
When food sources have been depleted, the climate becomes hostile, or
individual survival is jeopardized by some other adverse change in
living conditions, these organisms switch to sexual forms of
reproduction. Sexual reproduction ensures a mixing of the gene pool of
the species. The variations found in offspring of sexual reproduction
allow some individuals to be better suited for survival and provide a
mechanism for selective adaptation to occur. The meiosis stage of the
sexual cycle also allows especially effective repair of DNA damages
In addition, sexual reproduction usually results in the formation of a
life stage that is able to endure the conditions that threaten the
offspring of an asexual parent. Thus, seeds, spores, eggs, pupae, cysts
or other "over-wintering" stages of sexual reproduction ensure the
survival during unfavorable times and the organism can "wait out"
adverse situations until a swing back to suitability occurs.