which is the largest of it?
The blue whale
Animal
The blue whale ("Balaenoptera musculus") is the largest animal that has ever lived, weighing up to at least 190 tonnes and measuring up to long. The largest extant terrestrial animal is the African bush elephant ("Loxodonta africana"), weighing up to 12.25 tonnes and measuring up to long. The largest terrestrial animals that ever lived were titanosaur sauropod dinosaurs such as "Argentinosaurus", which may have weighed as much as 73 tonnes. Several animals are microscopic; some Myxozoa (obligate parasites within the Cnidaria) never grow larger than 20 µm, and one of the smallest species ("Myxobolus shekel") is no more than 8.5 µm when fully grown.
what characteristics do all the organisms in the animal kingdom share Animals are eukaryotic, multicellular, heterotrophic, respire aerobically what is meant by the third feature? A heterotroph  is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. can you give example of such species? All animals and fungi, ome bacteria and protists, and many parasitic plants. regarding the first one; how are they classified? Insecta, Pisces, Amphibia, Aves, and Mammalia.
wiki:9100361
Animal [SEP] Largest and smallest
The blue whale ("Balaenoptera musculus") is the largest animal that has ever lived, weighing up to at least 190 tonnes and measuring up to long. The largest extant terrestrial animal is the African bush elephant ("Loxodonta africana"), weighing up to 12.25 tonnes and measuring up to long. The largest terrestrial animals that ever lived were titanosaur sauropod dinosaurs such as "Argentinosaurus", which may have weighed as much as 73 tonnes. Several animals are microscopic; some Myxozoa (obligate parasites within the Cnidaria) never grow larger than 20 µm, and one of the smallest species ("Myxobolus shekel") is no more than 8.5 µm when fully grown.