It is distributed in the intertidal zone to the seabed thousands of meters deep, mostly concentrated in the rocky seabed or sandy seabed in the coastal zone, or widely distributed or limited to specific sea areas, which varies from species to species. Sea urchin is the earliest model organism used in the history of biological science, and its eggs and embryos play an important role in the development of early developmental biology. It is one of the longest-lived marine life on earth.
Second, shellfish, that is, a class of mollusks. It is an animal with three layers of germ layers, symmetrical left and right, and true cavity. The eucoeloma of mollusks is formed by the split cavity method, that is, the body cavity formed by mesoderm. However, the eucoeloma of mollusks is underdeveloped and only exists in the pericardial cavity and gonad cavity. Mollusks differ greatly in morphology, but they can be divided into four parts in structure: head, feet, viscera and mantle.
Jelly Fish (English name: Jellyfish) is an important plankton in aquatic environment, including Cephalopods, Cephalopods, Cruciferae and Cubes. Jellyfish is a very beautiful aquatic animal. Its shape is like a transparent umbrella, and the diameter of the umbrella is large or small. The diameter of the umbrella of the big jellyfish can reach 2 meters. There are some whisker-like tentacles on the edge of the umbrella, and some tentacles can be as long as 20-30 meters.
4. Sharks belong to cartilaginous fishes and a subclass of vertebrates. They are marine, a few species enter fresh water, and they are a group of medium and large marine fish that swim very fast.
The endoskeleton of sharks is completely composed of cartilage, which is often calcified, but there is no real bone tissue. The exoskeleton is not developed or degenerated. The body is often covered with skin teeth (thin-walled scales), with various teeth and hard muscles, but the membranous bone never exists and the skull is seamless. The upper forehead is composed of palatal cartilage and the lower forehead is composed of Mayer cartilage.
5. Dolphin is the general name of a class of aquatic mammals in Dolphinidae (scientific name: Delphi). They are small or medium-sized toothed whales, which widely live in the oceans of the world, and are also distributed in brackish fresh water near inland seas and river estuaries, and some species are also found in inland rivers. Usually like to live in groups and prey on fish, squid and so on.