How Many Animal Phyla are There?

The animal phylum includes more than 40,000 animals living in modern times, and is divided into three subphylums: chordal animal phylum, mollusk phylum, and timid animal phylum.

Animal door

The chordal phylum includes more than 40,000 animals that live in modern times and is divided into three subphylums:

They are a door to the animal world of tardigrade animals, and are commonly known as

The highest animal in the animal kingdom. Its common feature is that it has

Mollusca (Mollusca) The second gate of the animal kingdom. The body is soft, symmetrical, and not segmented. It consists of the head, feet, visceral sac, coat and shell. Because most mollusks have shells, they are commonly referred to as shellfish. There are more than 100,000 species of this species, which are widely distributed, from cold to temperate to tropical, from oceans to rivers and lakes, from plains to mountains. For example, abalone, baby, field snail, snail, cormorant, oyster, clam, octopus, squid and so on. Molluscs have antennae, eyes, balance sacs, and olfactory devices. The number and shape of the antennae are different: the new disc shell has 2 small antennae in front of the mouth; the gastropods have 1 pair of tentacles in the anterior gill subclass; the pulmonary snails have 2 pairs of antennae, 1 of which has a pair of large antennae. The olfactory angle of the posterior gills and the olfactory depression of the cephalopods are similar to the large antennae of the snails. In bivalves, sensory cells play a tactile role at the edges of the mantle and the tentacles of the water pipe. Mollusc fertilized eggs are typical spiral-shaped cleavages. They form a gastrointestinal embryo by outsourcing or introversion or by both. After the gastrointestinal embryo is formed, it quickly develops into a free-swimming tranny larva. Some species develop directly from adult larvae into larvae, but most species develop from face larvae to larvae before they become adult. Most marine gastropod trojan larvae spend in egg bags, and some pre-gills and freshwater gastropods, snails, and disc larvae spend in egg bags. The mussels that live in fresh water are specialized in the larvae of the discoid larvae that adapt to the parasitic life. This larva is parasitic on the gills, fins or other parts of the fish, forming cysts on the fish. The larva obtains nutrition from the host's body, gradually develops into an adult, bursts out of the capsule, and sinks to the bottom of the bottom camp to live. Cephalopod egg division is a type of incomplete division of the discoid division and is a direct development. Mollusk phyla has many finger fossils that can be used as an indicator of sedimentary environment in the history of geology. At the bottom of the Cambrian system in the world and China, there have been fossils of veneer and other mollusks. Many chrysanthemums in the Mesozoic have become fossils that are divided and contrasted in the intercontinental zone, and some can be used to understand the temperature of the ancient waters. And salinity; snail fossils can reflect the quaternary climate and environment.

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