Animal introduction:

An animal is a creature. They generally feed on organic matter, are sentient creatures, and can move or move autonomously. Man is also one of the animals. According to fossil research, the earliest animals on earth originated from the ocean. After a long geological period, early marine animals gradually evolved into various branches, enriching the early life forms of the earth.

Historical evolution:

Prehistoric animals appeared in their respective activities before human beings appeared. Later, they became extinct in the ever-changing living environment. However, the animals on the earth are still evolving and multiplying from low to high and from simple to complex, with today's diversity.

Scientists divide the known living animals into invertebrates and vertebrates according to whether there are thorns in animals. Scientists have identified more than 46,900 species of vertebrates. Including cartilaginous fish such as sharks and rays, bony fish such as carp, yellow croaker and grass carp, amphibians such as frogs and giant salamanders, reptiles such as snakes and lizards.

Birds such as chickens, pigeons and sparrows, and mammals such as monkeys and red pandas. Scientists have also discovered more than 654.38+300,000 species of invertebrates. Most of these animals are insects, most of which are beetles.

Sponges, earthworms, squid, oysters, red starfish, jellyfish, spiders, corals, radiolarians, roundworms, pork tapeworms, worms, snails and slugs all belong to invertebrates. The bodies of all members of the animal kingdom are heterotrophs composed of cells. On May 17, 2023, scientists discovered that ctenophore is the "brother and sister" of all animals, and strong evidence solved the mystery of the earliest animal evolution.

The earliest animals:

Most animals known to appear in fossils are marine species during the Cambrian explosion 540 million years ago. The CAMBRIAN explosion is a great challenge to evolution. The ocean is the largest ecological group on the earth, and it is the first place where life breeds on the earth.

Moreover, the early life of the earth only existed in an environment with water, and the earliest animals and marine animals were invertebrates. It was not until 500 million years ago that the earliest vertebrate turtles appeared in the ocean.