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The hemipenis is the intromittent organ of Squamata, [4] which is the second largest order of vertebrates with over 9,000 species distributed around the world. They differ from the intromittent organs of most other amniotes such as mammals, archosaurs and turtles that have a single genital tubercle, as squamates have the paired genitalia remaining separate. [5]
Parthenogenesis is a mode of asexual reproduction in which offspring are produced by females without the genetic contribution of a male. Among all the sexual vertebrates, the only examples of true parthenogenesis, in which all-female populations reproduce without the involvement of males, are found in squamate reptiles (snakes and lizards). [1]
The increase in stress level causes cloacal gaping, allowing for the courting male to more easily insert his reproductive organ into the female. [1] Snake mating systems are generally believed to be polygynous, where males copulate with multiple females. Many researchers have assumed that multiple male courtships are successful without ...
The cardiovascular system of snakes is unique for the presence of a renal portal system in which the blood from the snake's tail passes through the kidneys before returning to the heart. [79] The circulatory system of a snake is basically like those of any other vertebrae. However, snakes do not regulate internally the temperature of their blood.
Since first appearing during the age of dinosaurs, snakes have authored an evolutionary success story - slithering into almost every habitat on Earth, from oceans to tree tops. Scientists ...
Squamata (/ s k w æ ˈ m eɪ t ə /, Latin squamatus, 'scaly, having scales') is the largest order of reptiles, comprising lizards (including snakes).With over 12,162 species, [3] it is also the second-largest order of extant (living) vertebrates, after the perciform fish.
Many species of snakes have skulls with several more joints than their lizard ancestors, enabling them to swallow prey much larger than their heads (cranial kinesis). To accommodate their narrow bodies, snakes' paired organs (such as kidneys) appear one in front of the other instead of side by side, and most have only one functional lung .
Parthenogenetic offspring in species that use either the XY or the X0 sex-determination system have two X chromosomes and are female. In species that use the ZW sex-determination system, they have either two Z chromosomes (male) or two W chromosomes (mostly non-viable but rarely a female), or they could have one Z and one W chromosome (female).