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The mammalian male reproductive system contains two main divisions, the penis and the testicles, the latter of which are where sperm are produced and usually held in a scrotum. In humans, both of these organs are outside the abdominal cavity, but they can be primarily housed within the abdomen in other animals.
Parthenogenesis (/ ˌpɑːrθɪnoʊˈdʒɛnɪsɪs, - θɪnə -/; [1][2] from the Greek παρθένος, parthénos, 'virgin' + γένεσις, génesis, 'creation' [3]) is a natural form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization. In animals, parthenogenesis means development of an ...
Parthenogenesis is a form of asexual reproduction in which growth and development of embryos occur without fertilization. In animals, parthenogenesis means development of an embryo from an unfertilized egg cell. The first all-female (unisexual) reproduction in vertebrates was described in the Amazon molly in 1932. [33]
Sex-determination system. Some chromosomal sex determination systems in animals. A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. [1] Most organisms that create their offspring using sexual reproduction have two common sexes and a few less common intersex variations.
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] Unlike most organ systems, the sexes of ...
Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of the defining features of marsupials is their unique reproductive strategy, where the young are born in a relatively undeveloped state and then nurtured within a pouch on their mother's ...
Echinoderms are unusual in having both a coelomic circulatory system (the water vascular system) and a haemal circulatory system, as most groups of animals have just one of the two. [41] Haemal and perihaemal systems are derived from the original coelom, forming an open and reduced circulatory system. This usually consists of a central ring and ...
The reproductive system of marine gastropods such as those from class Opisthobranchia and order Archaeogastropoda from the class Prosobranchia, is a continuous cycle of alternating male and female reproductive role prevalence. Immediately after spawning in late summer, the predominance of the female reproductive functions are terminated and ...