body parts of animal are arranged around a central axis in radial symmetry.
body parts of animal are arranged around a central axis in radial symmetry.
body parts of animal arranged around a central axis?
radial symmetry
like all echinoderms, sea cucumbers possess pentaradial symmetry, with their bodies divided into five nearly identical parts around a central axis. however, because of their posture, they have secondarily evolved a degree of bilateral symmetry. for example, because one side of the body is typically pressed against the substratum, and the other is not, there is usually some difference between the two surfaces (except for apodida). like sea urchins, most sea cucumbers have five strip-like ambulacral areas running along the length of the body from the mouth to the anus. the three on the lower surface have numerous tube feet, often with suckers, that allow the animal to crawl along; they are called "trivium". the two on the upper surface have under-developed or vestigial tube feet, and some species lack tube feet altogether; this face is called "bivium".
sea cucumber
the layout of the vernacular residential houses also reflects the patriarchal ethical concepts and ritual-level thinking. reflected in the architecture, it is the dedication and preference of the central axis. the courtyard is always located at the centerline, and the central axis runs through the entire building. the layout of the building is symmetrical and balanced, with a smooth and dignified outline, reflecting a rigorous and honest style. if there is more than one courtyard, it is generally developed along the central axis or vertically to the axis. the furniture in the hall of the house is symmetrically arranged along the central axis. the indoor core space is organized by screens and main seats inside. in the distribution of family members' rooms, it is strongly influenced by the confucian ethics and morals，which advocates to distinguish between different hierarchy status.
vernacular residential architecture of western sichuan