All about Pets

Animals are a traditionally (since the time of Aristotle) distinguished category of organisms, currently considered as a biological Kingdom. Animals are the main object of Zoology study.

The animals are thought to have descended from flagellate unicellulars, and their closest known living relatives are choanoflagellates, collared flagellates morphologically similar to the choanocytes of some sponges. Molecular studies have determined the place of animals in the supergroup Opisthokonta, which also includes choanoflagellate, fungi, and a small number of parasitic protists. The name Opisthokonta refers to the posterior location of the flagellum in a mobile cell, as in most animal spermatozoa, while other eukaryotes tend to have an anterior flagellum.

It is believed that the first animals appeared in the middle of the Proterozoic. This is a creature called Grypania in the form of spiral carbon bands, whose prints are found in rocks aged 1.9—1.4 billion years in the vicinity of lake Superior. There is no doubt that the find belongs to animals. Some researchers consider it the remains of primitive multicellular algae-eukaryotes or a highly developed colony of cyanobacteria.

Another presumed ancient animal is called Horodyskia, found in 1.44 billion-year-old sediments in North America and 1.4-1.07 billion years in Australia.