The body wall of cnidarians consists of an outer layer or epidermis, an inner layer or gastrodermis, and a middle layer or mesoglea. Cnidarians lack organs and posses a primitive nervous system known as a neural net. Cnidarians exhibit two basic structural forms, a medusa and a polyp. The medusa form is a free-swimming structure which consists of an umbrella-shaped body (called a bell), a fringe of tentacles that hang from the edge of the bell, a mouth opening located on the underside of the bell, and a gastrovascular cavity.
Tropic of Capricorn, parallel of latitude at 23Â°30â south of the equator; it is the southern boundary of the tropics.This parallel marks the farthest point south at which the sun can be seen directly overhead at noon; south of the parallel the sun appears less than 90Â° from the northern horizon at any day of the year.ropic of Capricorn, parallel of latitude at 23Â°30â south of the equator; it is the southern boundary of the tropics.
â¢ Tropic of Cancer: Encloses the North Temperate Zone with the Arctic Circle. â¢ The Equator: Divides the earth in North and Southern Hemispheres. The are around the Equator is referred to as the Tropics and is limited northward by the Tropic of Cancer and southward by the Tropic of Capricorn. â¢ Tropic of Capricorn: Encloses the South Temperate Zone with the Antarctic Circle. â¢ Antarctic Circle: Is the boundary of the South Frigid Zone to the south. Arctic Circle. The Arctic Circle parallel that is currently positioned at 66Â° 33â 46â in the Northern Hemisphere ( or 66.5628Â°). The position of the Arctic Circle fluctuates by about 49 ft each year due to the Earthâs axial tilt that is determined by tidal forces resulting from the pull of the moon on the Earthâs waters.