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Animals are unique in having the ball of cells of the early embryo (1) develop into a hollow ball or blastula (2). Animals have several characteristics that set them apart from other living things. Animals are eukaryotic and multicellular.
Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million in total. Animals range in size from 8.5 millionths of a metre to 33.6 metres (110 ft) long and have complex interactions with each other and their environments, forming intricate food webs .
Deserts, plains, grasslands, woodlands, forests, and other areas including the most developed urban areas, all have distinct forms of wildlife. While the term in popular culture usually refers to animals that are untouched by human factors, most scientists agree that much wildlife is affected by human activities. [2]
In the English language, many animals have different names depending on whether they are male, female, young, domesticated, or in groups. The best-known source of many English words used for collective groupings of animals is The Book of Saint Albans , an essay on hunting published in 1486 and attributed to Juliana Berners . [1]
Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia (/ ˌ æ n ɪ ˈ m ɑː l i ə /). With few exceptions, animals consume organic material, breathe oxygen, have myocytes and are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development.
Animals are a major group of organisms, classified as the kingdom Animalia. This category includes animals, their study, and their classification.
A mammal (from Latin mamma 'breast') [1] is a vertebrate animal of the class Mammalia ( / məˈmeɪli.ə / ). Mammals are characterized by the presence of milk -producing mammary glands for feeding their young, a neocortex region of the brain, fur or hair, and three middle ear bones.
