Which animals do not have a backbone, animals that do not have a backbone

The more common ones are sand silkworms, earthworms, leeches, jellyfish, blood-sucking insects, planarians, nematodes, etc. Invertebrates appeared relatively early, at least more than 1.1 billion years earlier than vertebrates. The so-called invertebrates, simply put, mean that there is no vertebral column on the dorsal side, and such animals are invertebrates.

According to the evolutionary order of invertebrate propellers, it includes groups such as protozoa, sponges, coelenterates, flattened animals, nematozoans, annelids, molluscs, arthropods, echinoderms, etc.

For example: shellfish, mullet, starfish, sponges, jellyfish and corals, etc.

Protozoa: such as amoebae, paramecium, euglena, etc.

Coelenterates: such as polyps, jellyfish (jellyfish), hydroids, etc.

Nematoids: such as roundworms, pinworms, heartworms, etc.

Flattened animals: such as planarians, schistosomiasis, tapeworms, etc.

Echinoderms: such as starfish, sea urchins, sea cucumbers, sea lilies, etc.

Molluscs: such as clams, pearl oysters, squid, snails, various snails, octopus, etc.

Annelids: such as earthworms, leeches, sand silkworms, etc.

Arthropods: This is the most diverse group of animals in existence, with more than 1 million species, of which insects make up the majority. Common arthropods such as bees, flies, dragonflies, beetles, shrimps, crabs, centipedes, scorpions, spiders, horseshoe crabs, horseshoe crabs, etc.

Invertebrates are animals that do not have a vertebral column on the dorsal side, and they are the original form of animals. Its species account for 95% of the total number of animal species. It is distributed all over the world, and there are about 100 million species in existence.

Including protozoa, spiny shed skins, molluscs, flattened cea, annelids, coelenterates, arthropods, nematozoa, etc.

Specific invertebrates are: paramecium, anemones, jellyfish, roundworms, octopuses, jellyfish, earthworms, scallops, crabs, shrimps, dragonflies, ants, etc.

There are two types of organisms that have vertebrates but are not vertebrates, which are sponges and cnidarians.

Sponges are primitive multicellular organisms that have certain characteristics of vertebrates, such as intercellular matrix and collagen fibers, but they do not have real tissues and organs, nor do they have a nervous system and muscular system.

Cnidarians include jellyfish, corals, anemones, etc., which have a coelenteric structure and can ingest food, but their nervous systems are not complex enough and do not have a true muscular system.

Those that have vertebrates but are not vertebrates, are bacteria and protozoa, bacteria do not have vertebral vertebrae but their structure can simulate the form of vertebral vertebrates, whereas protozoa also have vertebral vertebrates but they do not belong to vertebrates.

Reptiles, mammals, birds, amphibians, fish, invertebrates.

An animal is a species of living organism. They generally feed on organic matter, can feel, can move in the wild, and can move autonomously or move things. Including people.

Introduction

According to fossil research, the first animals to appear on Earth originated from the ocean. After a long geological period, early marine animals gradually evolved various branches of repentance, enriching the early life forms on earth. Prehistoric animals appeared before the advent of humans and flourished during their respective periods of activity.

Later, they became extinct one after another in a constantly changing environment. However, the animals on Earth are still evolving and multiplying in a trend from the lowest to the higher, from the simple to the complex, and have the diversity they have today.

Scientists divide the extant animals known to humans into two major types: invertebrates and vertebrates, according to the presence or absence of a vertebrate in their bodies.