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HermaphroditismA Primer on the Biology, Ecology, and Evolution of Dual Sexuality$
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John Avise

Print publication date: 2011

Print ISBN-13: 9780231153867

Published to Columbia Scholarship Online: November 2015

DOI: 10.7312/columbia/9780231153867.001.0001

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Two Sexes in One

Two Sexes in One

Chapter:
(p.1) Chapter One Two Sexes in One
Source:
Hermaphroditism
Author(s):

John C. Avise

Trudy Nicholson

Publisher:
Columbia University Press
DOI:10.7312/columbia/9780231153867.003.0001

This chapter defines hermaphroditism, and contrasts male with female in diverse organisms. A hermaphrodite is a dual-sex organism that has the capacity to reproduce as both male and female during its lifetime. Hermaphroditism is relatively rare in vertebrates, but extremely common in plants and invertebrate animals. Anisogamy refers to the bimodal distribution of gametic sizes that characterizes all multicellular sexual species; by definition, male gametes are relatively small, and female gametes are relatively large. It arose early in the history of multicellular life, probably through a combination of evolutionary factors, including disruptive selection on gametic size, selection against sexual diseases housed in the cell cytoplasm, and the resolution of potential evolutionary conflicts between nuclear and cytoplasmic genomes. It implies that males have an inherent capacity to produce large numbers of small and energetically cheap gametes, whereas females can produce far fewer and individually more expensive gametes.

Keywords:   hermaphroditism, hermaphrodite, male, female, anisogamy, gametes, sexual diseases

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