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The locking is completed by circular muscles just inside the female's vagina; this is called "the knot" tightening thus preventing the male from withdrawing. The circular muscles also contract intermittently, which has the effect of stimulating ejaculation of sperm, followed by prostatic fluid, as well as maintaining the swelling of the penis ...
Many mammalian species have developed keratinized penile spines along the glans or shaft, which may be involved in sexual selection. These spines have been described as being simple, single-pointed structures or complex with two or three points per spine (strepsirrhines). [1] Penile spine morphology may be related to mating system. [2] [3]
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]
The reason why some researchers are skeptical about animals having a sense of humor is that it serves no evolutionary purpose. For humans, it's a bonding strategy. For humans, it's a bonding strategy.
This is a list of animals that have a naturally occurring hump or humps as a part of their anatomy. Humps may evolve, as a store of fat, as a heat control mechanism, as a development of muscular strength, as a form of display to other animals, or be apparent as a consequence of some behaviour such as the diving of whales. Enlarged humps have ...
In passive electrolocation, the animal senses the weak bioelectric fields generated by other animals and uses it to locate them. These electric fields are generated by all animals due to the activity of their nerves and muscles. A second source of electric fields in fish is the ion pump associated with osmoregulation at the gill membrane. This ...
Nature is full of many patterned animals, from the stripes on zebras, spots on leopards, to the intricate details on sea creatures.. Researchers have studied for a long time the biological ...
Burrs on a tree trunk in Norfolk, England. A burl (American English) or burr (British English) is a tree growth in which the grain has grown in a deformed manner. It is commonly found in the form of a rounded outgrowth on a tree trunk or branch that is filled with small knots from dormant buds.