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Animals

Animals (also called Metazoa) are multicellular eukaryotic organisms that form the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. 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 animal species in total. Animals range in length from 8.5 micrometres (0.00033 in) to 33.6 metres (110 ft). They have complex interactions with each other and their environments, forming intricate food webs. The kingdom Animalia includes humans but in colloquial use the term animal often refers only to non-human animals. The scientific study of animals is known as zoology.

Most living animal species are in Bilateria, a clade whose members have a bilaterally symmetric body plan. The Bilateria include the protostomes—in which many groups of invertebrates are found, such as nematodes, arthropods, and molluscs—and the deuterostomes, containing both the echinoderms as well as the chordates, the latter containing the vertebrates. Life forms interpreted as early animals were present in the Ediacaran biota of the late Precambrian. Many modern animal phyla became clearly established in the fossil record as marine species during the Cambrian explosion, which began around 542 million years ago. 6,331 groups of genes common to all living animals have been identified; these may have arisen from a single common ancestor that lived 650 million years ago.

Historically, Aristotle divided animals into those with blood and 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) and the Protozoa, single-celled organisms no longer considered animals. In modern times, the biological classification of animals relies on advanced techniques, such as molecular phylogenetics, which are effective at demonstrating the evolutionary relationships between taxa.

Humans make use of many other animal species, such as for food (including meat, milk, and eggs), for materials (such as leather and wool), as pets, and as working animals including for transport. Dogs have been used in hunting, while many terrestrial and aquatic animals were hunted for sports. Non-human animals have appeared in art from the earliest times and are featured in mythology and religion.

Are zoos ethical in the modern age?
No, zoos are good
Zoos provide quick and advanced medical care
Captive animals are able to get the medical care they need.
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Are zoos ethical in the modern age?
Yes, zoos are bad
Predators born in zoos are likely to die if released
Predatory animals born in captivity are unlikely to survive if released into their natural habitat.
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Are zoos ethical in the modern age?
Yes, zoos are bad
Zoo animals attack people
There have been many reported cases of animals injuring people at zoos.
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Are zoos ethical in the modern age?
Yes, zoos are bad
Zoos give animals poor health
Living in captivity is terrible for an animal's health.
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Are zoos ethical in the modern age?
Yes, zoos are bad
Zoos have inadequate living conditions
Ultimately, zoos would have to go to great architectural and environmental lengths to provide the animals with sufficient living space. Zoos cannot give an animal the environment it needs due to monetary and geographical circumstance.
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Are zoos ethical in the modern age?
Yes, zoos are bad
Zoos remove animals from their environment
Placing animals in zoos removes them from their natural environment.
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Are zoos ethical in the modern age?
No, zoos are good
Zoo animals have a longer life expectancy
Captive animals tend to live longer than their wild counterparts.
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Are zoos ethical in the modern age?
Yes, zoos are bad
Zoos are created for profit
Zoos force animals to provide entertainment for people.
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Are zoos ethical in the modern age?
Yes, zoos are bad
Zoos are unethical because they are dangerous for animals
Keeping animals in captivity disrespects their intelligence and puts them at risk of abuse. Humans do not have the right to trap animals in enclosures for the benefit of our own entertainment and research needs.
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Are zoos ethical in the modern age?
No, zoos are good
Zoos conserve endangered species
Zoos protect animals that have the threat of becoming extinct.
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Are zoos ethical in the modern age?
No, zoos are good
Zoos educate about exotic animals
People learn more information about exotic animals while visiting zoos.
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Are zoos ethical in the modern age?
No, zoos are good
Zoos provide research opportunities
Scientists are able to study and better understand animals and their natural environments.
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This page was last edited on Monday, 26 Oct 2020 at 18:21 UTC