Kingdom Animal


The animal kingdom , kingdom Animalia  or kingdom Metazoa , is the kind of kingdom that includes all animals that exist on the planet. Let us remember that animals are multicellular , eukaryotic organisms , which are heterotrophs , which means that they obtain their nutrition from organic sources . Most animals eat by ingesting other organisms or by breaking down organic material. All animals, with the exception of sponges , are made up of cells organized in tissues that have been created and specialized for somedetermined function . As a result, most animals are capable of complex behavioral responses and rapid movements.


What is the animal kingdom?

The animal kingdom is a set of living beings that have or share relevant characteristics that make them different from others, that have morgological and behavioral diversity and that are divided into phyla or taxonomic organizations .

  • What does it consist of
  • Characteristics of the animal kingdom
  • Source
  • Evolution
  • Classification of the animal kingdom
  • Habitat
  • Nutrition
  • Reproduction
  • Breathing
  • Cell types of the animal kingdom
  • Domain of the animal kingdom
  • Examples of animals
  • Importance

What does it consist of

The animal kingdom is a diverse group of organisms that share certain characteristics . It is undoubtedly the largest of all the kingdoms with more than a million species. It can be said that they are all those organisms that we generally know by the name of animals , beings that we can also come to recognize by the characteristics of their movements and their reactions to the environment .


Characteristics of the animal kingdom

The main characteristics of the animal kingdom are the following:

  • They are eukaryotic so their cells contain a defined cell nucleus and a nuclear membrane.
  • They are multicellular because they have two or more cells with specialized functions.
  • They are heterotrophs because they must ingest and absorb nutrients from other living beings since they do not have the ability to produce their own.
  • They are aerobic because they breathe either through the skin , or with the oxygen they get from the environment.
  • They reproduce through male and female sex cells, although some invertebrates reproduce asexually with mitosis .
  • They have the ability to develop and be born in different ways depending on their species, so they can be oviparous (they develop and hatch from eggs), viviparous (they develop and hatch directly from the mother) and ovoviviparous (the eggs remain within the female until birth).
  • They have a series of tissues and organs that make them different and thanks to them they have skin, muscles, organs, nerve endings, digestive system and nervous system, among others.
  • They have symmetry which depends on their physical structure.


According to experts, the animal kingdom has its origin in a microorganism that would be their common ancestor . It is known by the name of choanoflagellates and is believed to have existed more than 600 million years ago. Scientists explain that choanoflagellates possess genes involved in animal development with variations between species.


It is believed that the first animals that existed were aquatic animals that lived on land approximately 500 million years ago, where the main groups of invertebrates also emerged . Later, there was enough vegetation on the land for some of the invertebrates to begin to colonize the terrestrial environment . Over time the primitive chordates appeared that were more evolved and possessed a nervous system, the spinal column . The reptiles , amphibians then be born when began to evolve and then came the mammals, which expanded into thousands of habitats once the dinosaurs disappeared.

Classification of the animal kingdom

The classification of the animal kingdom is as follows:


They have a spinal column that supports the body. In this group there is a special consideration that corresponds to fish are vertebrate beings. Some 50,000 species of vertebrates have been identified and there are five different groups of them:

  • Fish : they were among the first vertebrates and evolved from animals with backbones about 500 million years ago. They are adapted to the aquatic environment , breathe through gills and move through fins . They can have cartilage or bone skeletons.
  • Mammals : they are the last animals to emerge on earth and there are more than 5,000 species that are warm-blooded , give birth to live young, and are fed breast milk after birth.
  • Birds : they are homeothermic reptiles and they descend from dinosaurs . There are about 10,000 species of birds in the world except in polar regions with extreme temperatures. Almost all can fly although there are some exceptions.
  • Reptiles : they were the first vertebrates that managed to live out of water and the group includes turtles, lizards, snakes, crocodiles and tuátaras. Their blood is cold and their skin is covered with hard and dry scales , they can also regulate their temperature .
  • Amphibians : they are cold-blooded but their skin is smooth in addition to having 4 legs . They live in terrestrial habitats and lay their eggs in fresh water .


They constitute the oldest form of animal life on the planet, they are classified into about 30 phyla, and it is the group with the largest number .


Habitat is the place or area in which a certain animal or plant species lives . It is the space that has all the right conditions for a species to survive and reproduce properly to perpetuate the species. In this way, we have aquatic and terrestrial habitats .


Animals that belong to the animal kingdom are heterotrophs and feed directly or indirectly on other living beings.  Their diet varies depending on the species and they can feed on plants and other species. According to the diet, they are classified into:

  • Carnivores : they eat meat and can hunt their prey to eat them. Some of them feed on lifeless animals and are known as scavengers .
  • Herbivores : they feed on plants and vegetables although they can also feed on animal proteins such as eggs.
  • Omnivores : they feed on animals and vegetables , so their diet is mixed.


The Animal Kingdom is very diverse and in it there are different patterns of reproduction and cycles of life . There is asexual reproduction in which there is a single parent and there are no reproductive organs or sex cells involved, it does not need mating but it does not generate genetic diversity either . Sexual reproduction includes all the processes of biparental reproduction which involve two individuals . This type of reproduction includes haploid sex cells or gametes that reproduce by meiosis. Sexual reproduction includes gametogenesis , mating, and fertilization .


Respiration is carried out in the mitochondria through a process that consumes oxygen, releasing carbon dioxide and obtaining energy . All animals need a respiratory system to carry out this gas exchange . Depending on the type of respiratory system, we can find four different types of respiration:  cutaneous , branchial, tracheal and pulmonary .

Cell types of the animal kingdom

All living things are made up of cells. In the case of the animal kingdom, all the living beings that compose it have eukaryotic cells since they have a well-differentiated nucleus, with a cell membrane , nucleus and genetic material and they are also multicellular organisms since they are made up of a large number of them. The cells of the animal kingdom can be white blood cells , in the form of neurons, ciliated, flattened, somatic and reproductive .

Domain of the animal kingdom

In biology, the taxonomic category used for biological classification is known by the domain name , above the kingdom and the superkingdom. All organisms that have a complex type of anatomy , along with some other organisms that are simpler or unicellular, belong to the Eukarya domain, also known as eukaryotes , which in this case includes the animal kingdom.

Examples of animals

Some examples of animals that belong to the animal kingdom are the following: humans, the ant, bees, elephants, domestic cats and dogs, butterflies, clams, salmon, dolphins, shark, bats and earthworms.


All the animals that we find in the animal kingdom play a key role or ecological niche within all ecosystems , it is for this reason that the animal kingdom is very important, because it helps to control the different populations that some species exert on others. They are also of ecological importance because they help to control the population of other animals, they are an important source for the economy and for the feeding of other living beings.

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