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The first fossilized evidence of sexual reproduction in eukaryotes is from the Stenian period, about 1.05 billion years old. [19] [20]Biologists studying evolution propose several explanations for the development of sexual reproduction and its maintenance.
The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction.Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system. [1]
In population ecology and demography, the net reproduction rate, R 0, is the average number of offspring (often specifically daughters) that would be born to a female if she passed through her lifetime conforming to the age-specific fertility and mortality rates of a given year.
The American Fertility Society (now American Society of Reproductive Medicine) Classification distinguishes: . Class I—Müllerian agenesis (absent uterus). This condition is represented by the hypoplasia or the agenesis (total absence) of the different parts of the uterus: