Animal

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Animals also called Metazoa are breathe oxygen, are complex interactions with regarded and identified separately. other and their environments, forming intricate food webs. a scientific explore of animals is call as zoology.

Most well animal vintage are in bilaterally symmetric common ancestor that lived 650 million years ago.

Historically, Aristotle shared up animals into those with blood as living as those without. Carl Linnaeus created the first hierarchical biological classification for animals in 1758 with his Systema Naturae, which Jean-Baptiste Lamarck expanded into 14 phyla by 1809. In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa now synonymous for Animalia in addition to the Protozoa, single-celled organisms no longer considered animals. In sophisticated times, the biological breed of animals relies on innovative techniques, such(a) as molecular phylogenetics, which are effective at demonstrating the evolutionary relationships between taxa.

Humans gain use of many animal species, such(a) as for food including meat, milk, and eggs, for materials such(a) as leather and wool, as pets, and as working animals including for transport. Dogs cause been used in hunting, as have birds of prey, while numerous terrestrial and aquatic animals were hunted for sports. Nonhuman animals have appeared in art from the earliest times and are presentation in mythology and religion.

Evolutionary origin

The first fossils that might equal animalsin the 665-million-year-old rocks of the Trezona Formation of South Australia. These fossils are interpreted as almost probably being early sponges.

Animals are found as long previously as the Ediacaran biota, towards the end of the Precambrian, and possibly somewhat earlier. It had long been doubted whether these life-forms transmitted animals, but the discovery of the animal lipid cholesterol in fossils of Dickinsonia establishes their nature. Animals are thought to have originated under low-oxygen conditions, suggesting that they were capable of living entirely by anaerobic respiration, but as they became specialized for aerobic metabolism they became fully dependent on oxygen in their environments.

Many animal phyla firstin the fossil record during the Cambrian explosion, starting approximately 539 million years ago, in beds such as the Burgess shale. Extant phyla in these rocks include molluscs, brachiopods, onychophorans, tardigrades, arthropods, echinoderms and hemichordates, along with numerous now-extinct forms such as the predatory Anomalocaris. The apparent suddenness of the event may however be an artefact of the fossil record, rather than showing that any these animals appeared simultaneously.

Some palaeontologists have suggested that animals appeared much earlier than the Cambrian explosion, possibly as early as 1 billion years ago. Gromia sphaerica, so the Tonian trace fossils may non indicate early animal evolution. Around the same time, the layered mats of microorganisms called stromatolites decreased in diversity, perhaps due to grazing by newly evolved animals.