ANIMAL KINGDOM: what it is, characteristics, classification and examples - Summary!

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Did you know that, at present, the total of known species of the Animalia kingdom constitute only 20% of the totality of living animals on the planet? And, if we go back to the total animal life that ever existed on the face of the Earth, this figure drops to 1%. These surprising data allow us to get an idea of the immense variety of life forms that the Kingdom of animals hides under its evolutionary history. To get closer to the knowledge of this Kingdom, numerous specialists dedicate their efforts every year to the characterization and in-depth knowledge of the Animalia kingdom, thus allowing the rest of society to delight us with their surprising scientific discoveries.

Do not miss this article by Ecologist Verde in which you will discover the most interesting and striking data of the Animalia kingdom: what is it, characteristics, classification and examples.

What is the Animalia kingdom

The Animalia Kingdom It constitutes, together with the Planate, Fungi, Protista and Monera kingdoms, the five famous taxonomic kingdoms of biological evolution in which the different forms of life that exist (and have existed) on Earth are grouped. As the name suggests, each and every one of the different animal species, grouped in a hierarchical system based on the homologous characters that they share with each other. In this way, animals constitute a large, ancient and well-defined "branch" within the evolutionary tree of life, which originated about 600 million years ago.

Zoology is the part of biology in charge of the exhaustive study of the Animalia kingdom, having as some of its main objectives to discover all the animal species that exist, reconstruct their evolutionary relationships and reflect these relationships in the construction of a taxonomic system.

Characteristics of the Animalia kingdom

The different species that belong to the Animalia kingdom are distributed throughout each and every one of the various ecosystems of the biosphere, with zoogeography being the science in charge of this study of the geographical distribution of animals. Let's see, next, more characteristics of the animal kingdom:

  • All animals are multicellular organisms, whose cells are characterized by the presence of a nucleus well bounded by a membrane, that is, they are eukaryotic organisms.
  • Are heterotrophic beings, that is, they depend on the consumption of other organisms to cover their nutritional needs. They thus have different strategies for capturing and processing the wide variety of foods they consume, as well as regulation of the ingestion and digestion of said foods. Learn more about Heterotrophic Organisms: what they are, characteristics and examples with this other article.
  • They have different locomotion systems that allow them to move and move, as well as the presence of integuments and other support and protection systems.
  • The morphology and size of the animals is surprisingly complex and variable.
  • A complex nervous system and sense organs characterize the vast majority of groups of animals. Made up of a network of neurons and different junction points between nerves, the process of synapses and nervous coordination confers on animals one of the most amazing capacities for interspecific relationships, that is, to relate to other living beings and the nature that surrounds them.
  • They have an endocrine system in charge of the regulation of the numerous and diverse hormones that intervene both in the metabolism of animals, as well as in their behavior and social and reproductive relationships.
  • Animals have circulatory systems to achieve a fast and efficient transport of nutrients and other dissolved substances that guarantee the correct functioning of their organs. These circulation systems transport different body fluids, such as blood, and are sometimes characterized by being open systems (as in arthropods) or closed systems (as in vertebrates).
  • Gas exchange takes place from the complex breathing process, for which animals have various strategies and organs adapted to meet the respiratory needs of the body. The pulmonary respiratory system of mammals, the gill of fish and the tracheal system of arthropods stand out. In other groups of animals, such as some amphibians, respiration is cutaneous, through the skin.

Classification of the kingdom Animalia

Thanks to the study of Phylogeny, zoologists make known the great diversity of animals that exist, taking into account their evolutionary origins, organization models and set of biological properties that relate or distinguish them from each other. For example, the presence or absence of bones allows animals to be classified as vertebrates or invertebrates.

The animal kingdom classification It is currently very complex, recognizing up to 32 different edges. Among them, the best known and most abundant phyla, in order from least to greatest anatomical and functional complexity, are:

  • Poriferous or sponges (9,000 species)
  • Cnidarians (10,000 species)
  • Flatworms or flatworms (20,000 species)
  • Roundworms or nematodes (25,000 species)
  • Annelids or ringworms (17,200 species)
  • Mollusks (93,000 species)
  • Arthropods or jointed legs (1,200,000 species)
  • Echinoderms (7,000 species)
  • Chordates (64,788 species)

To this last edge belong the mammals, birds, reptiles, amphibians and fish; all of them characterized by the presence of a "dorsal cord" during their embryonic development, which is maintained throughout the life of many of the chordate species (in humans, Homo sapiens sapiens, said dorsal cord is the so-called backbone, vital for the correct locomotion and development of the nervous and cognitive abilities that characterize us as a species).

Examples from the Animalia kingdom

Let's put some examples from the animal kingdom, following the classification in the previous section, to learn more about the great diversity of species that fill every corner of the biosphere with life:

  • Poriferous: purple tubular spongeAplysina archeri), freshwater sponge (Spongilla alba) and vitreous sponge (Aphrocallistes vastus)
  • Cnidarians: jellyfish (subphylum Medusozoa), anemones and corals (subphylum Anthozoa).
  • Flatworms: planaria (genus Prostheceraeus), flukes (class Trematoda) and tapeworm (Taenia saginata).
  • Nematodes: potato root nematode (genus Globodera), American necator (Necator americanus) and pinworm (Enterobius vermicularis).
  • Annelids: leeches (class Haemadipsa), earthworms (subclass Oligochaeta) and sea feather dusters (class Sabellida).
  • Mollusks: clams (Veneroida family), mussels (Mytilidae family), octopuses (Octopoda order) and squid (Teuthida order).
  • Arthropods: tarantulas (family Lycosidae), praying mantises (family Mantidae), centipedes (Class Chilopoda) and crabs (Crustaceans).
  • Echinoderms: starfish (class Asteroidea), sea urchins (class Echinoidea) and holothurians (class Holothuroidea).
  • Chordates: White shark (Carcharodon carcharias), Snow Leopard (Panthera uncia), Peregrine falcon (Falco peregrinus), Nile crocodile (Crocodylus niloticus), common salamander (Salamander salamander).

Then you can see images of the Animalia kingdom, specifically of each of the species mentioned in this list in order.

Importance of the Animalia kingdom

Like every link in the complex and surprising evolutionary chain of living beings, the kingdom of animals is of great importance. Each of the species that belong to this kingdom play an essential role within the proper functioning of the ecosystem in which it inhabits. In this way, we can talk about the importance of the Animalia kingdom in ecological terms, since each species is directly related to both its prey and its predators, in circles of energy transformation and balances of the habitat in which it develops and fulfills its vital functions.

As we can see, it is complex to determine for a single purpose the importance of the animal kingdom, going beyond the small and limited vision that human beings may have regarding the existence of the different groups of animals that we have been discovering throughout this article.

If you want to read more articles similar to Kingdom Animalia: what it is, characteristics, classification and examples, we recommend that you enter our Biology category.

  • Núñez-García, R. M. & Meraz, J. (2009) A look at the Animalia Kingdom from the phylogenetic structural perspective. Latin American magazine Ciencia y Mar. Volume 37, pp: 56-68.
  • Hickman, C. et al. (2003) Zoology: Comprehensive Principles, 5th ed. Madrid: McGraw-Hill Interamericana of Spain, pp: 10-15; 199-215.
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