What are Metazoans? What are metazoans

Metazoans are divided into metaphytes and metaphytes, such as thallophytes with a lamellar structure, while metaphytes are mostly multicellular animals, and the reliable fossil record is from the earliest Ediacara fauna (ediacarafauna).

With the evolution of organisms, the cells in multicellular organisms begin to differentiate and divide labor. Different cells perform different physiological functions, i.e. there is differentiation of tissues and organs. We call this organism composed of multiple cells and differentiated tissues and organs metazoans.

Metazoans may have appeared between 1 and 700 million years ago. The fossil record of metazoans that we know is about 600 million to 700 million years old and exists in many parts of the world. The most famous of these is the Ediacaran Fauna Cluster, discovered in Australia in 1946, which consists of a number of fossilized soft impressions of animals resembling jellyfish and worms, without hard shells (Figs. 2-34).

From the fossils, these organisms already have highly differentiated tissues and organs, indicating that they are no longer the most primitive type. They represent the first radiative evolution after the emergence of metazoans. Generally speaking, the biological world from the emergence of life to the emergence of metazoan organisms is dominated by tiny prokaryotic organisms (bacteria and cyanobacteria) and lower single-celled eukaryotic organisms, and the fossil record is very poor and monotonous.

A type of fossil known as stromatolite, the most common type of fossil 600 million years ago, is a layered bio-sedimentary structure formed by a mat-like colony of fungal algae during the metabolic activity and growth of life. The biological evolution of this period was the evolution of cellular structures (from prokaryotic cells to eukaryotic nematocytes) and metabolic pathways (from anaerobic respiration to aerobic exhalation). The emergence of metazoan marks the evolution of organisms into the development of the complexity of tissues and organs and the diversification of species, that is, biological, phylogenetic evolution.

Animals that emerged in the later era such as pterohands, rodents, neocarnivores, and pinnacles.

Protozoa phylum Protozoa is the lowest class of eukaryotic single-celled animals in the animal kingdom, and the individual is composed of a single cell. In contrast to protozoa, all animals that are composed of multiple cells are called metazoans.

It is characterized by the fact that the body is composed of a large number of cells with differentiated morphology and division of functions. Unlike the cells of the population protozoa, which have both vegetative and reproductive functions, their germ cells and vegetative cells have obvious differentiation.

What kind of creatures live in the posthoric era, of course, it is to look at pigs and dog hair.

There is no such thing as metazoic, so do you want to ask about the Mesozoic?