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It occurs when the organism's sex changes at some point in its life. [1] A sequential hermaphrodite produces eggs (female gametes) and sperm (male gametes) at different stages in life. [2] Sequential hermaphroditism occurs in many fish, gastropods, and plants. Species that can undergo these changes do so as a normal event within their ...
The XX/XY sex-determination system is the most familiar, as it is found in humans. The XX/XY system is found in most other mammals, as well as some insects. In this system, females have two of the same kind of sex chromosome (XX), while males have two distinct sex chromosomes (XY).
The ZW sex-determination system is a chromosomal system that determines the sex of offspring in birds, some fish and crustaceans such as the giant river prawn, some insects (including butterflies and moths), the schistosome family of flatworms, and some reptiles, e.g. majority of snakes, lacertid lizards and monitors, including Komodo dragons.
Sexual differentiation is the process of development of the sex differences between males and females from an undifferentiated zygote. [1] [2] Sex determination is often distinct from sex differentiation; sex determination is the designation for the development stage towards either male or female, while sex differentiation is the pathway towards the development of the phenotype.
The female-biased sexual size dimorphism observed in many taxa evolved despite intense male-male competition for mates. [28] In Osmia rufa, for example, the female is larger/broader than males, with males being 8–10 mm in size and females being 10–12 mm in size. [29] In the hackberry emperor females are similarly larger than males. [30]
In a large number of organisms, the sex-determination systems presently observed are products of sex chromosome turnover. Sex chromosome turnover is a process defined as when the type of the sex chromosome changes as a product of a change in the identity of the sex-determining genes (such as by mutation) or by a change in their location. [ 29 ]
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The XY sex-determination system is a sex-determination system present in many mammals, including humans, some insects , some snakes, some fish , and some plants (Ginkgo tree). In this system, the sex of an individual usually is determined by a pair of sex chromosomes .