We explain to you what the animal kingdom is, what is its origin and its characteristics. In addition, how is its classification, taxonomy and examples.
What is the animal kingdom?
The animal or animal kingdom constitutes, together with the vegetable kingdom, fungi, protists and moneras, one of the possible ways in which biology classifies known life forms . It is one of the great traditional kingdoms, although the classification has varied markedly over more than 200 years of classification attempts.
The creatures contained in this kingdom are called animals, and are characterized by having an enormous ecological, morphological and behavioral diversity, since they are present throughout the planet. At the same time, they are distinguished from the other eukaryotic kingdoms by lacking chlorophyll (they do not make photosynthesis) and cell wall (present in plant and fungal cells), as well as by their reproduction almost entirely sexual and its capacity for autonomous and voluntary movement.
Around two million different species belong to the animal kingdom around the world, grouped into several taxa or edges, and in two broad categories: vertebrates and invertebrates. In this kingdom, in addition, the human being is also classified.
See also: Animal cell.
Origin of the animal kingdom
The first animals on the planet appeared during the so-called "Cambrian explosion" 540 million years ago, which consisted of an amazing diversification and proliferation of life (especially multicellular life or metazoans) in the seas of the early Earth. The reasons that triggered such an evolutionary boom are ignored, but some possible perpetrators would be the proliferation of oxygen resulting from dominant plant life, as well as the pressures exerted by volcanic and geochemical activity.
The first animal species were sea sponges, some of which could date even 600 million years ago, according to ongoing studies. But since then the animals have a strong presence in the fossil record, as they proliferated in the seas and then on the mainland and through the air.
Characteristics of the animal kingdom
The fundamental characteristics of the animal kingdom can be summarized in the following:
- They are polycellular and tissue eukaryotic organisms. This means that the bodies of animals are made up of tissues that, in turn, are made up of various types of cells organized among themselves. Even the smallest animals have a body made up of numerous cells, and these are of the eukaryotic type: they have a defined cell nucleus, which contains the genetic information of the individual. These cells also lack chloroplasts and cell walls.
- They are heterogeneous and aerobic metabolism. The metabolism of animals cannot produce their own food as plants do, so they must consume organic matter from other living things to survive. Said organic matter is digested until obtaining its essential nutrients and from it obtaining glucose, a biochemical molecule that will then be oxidized to obtain the energy (ATP) that sustains the body walking . Said oxidation is produced by breathing: oxygen is taken from the air or water (depending on the species) and CO2 is released.
- They have their own mobility. This is one of the main distinguishing features of animals: they can move at will, either in water, air or land, using specialized limbs: wings, fins, legs, legs. Thanks to this, they can change their habitats and find a more suitable one, escape from predators or chase their prey.
- They have symmetrical bodies. The bodies of animals can have two types of symmetry, that is, they can be divided into two identical halves. The first is the bilateral symmetry (the body is divided longitudinally) and the second is the radial symmetry (the body is divided based on its radius, since it is circular).
- They practice sexual reproduction. With some specific exceptions, in the case of animals capable of parthenogenesis, animal species reproduce sexually, that is, by means of the dome of two individuals of opposite sexes (male and female) and the exchange of gametes Sex cells equipped with half of the individual's genetic load, and which also have notoriously different sizes and shapes.
- Bodies structured by collagen. Unlike other life forms whose bodies are mainly composed of cellulose, animals have the collagen as their structural protein.
Classification of the animal kingdom
In principle, the animal kingdom can be classified into two large groups: vertebrates (62, 000 species) and invertebrates (95% of the total species) . As the name implies, vertebrates are those that have a skull and a spine or spine, composed of vertebrae; while invertebrates are those that do not have an articulated internal skeleton.
Other forms of classification attend to the specific habitat of animals, being able to distinguish between marine animals (from the sea and the oceans), aquifer (freshwater), terrestrial (from the mainland), flying (from the air), amphibians (mixed life between water and land), parasitic (those that live within the bodies of others) or urban (from the city).
Taxonomy of the animal kingdom
The animal kingdom comprises a vast number of edges or groups of species that share a well-defined body organization, among which are:
- Porfer. Nearly 9, 000 species of immobile, benthic and body sponges with inhaling pores.
- Cnidarians Around 10, 000 species of simple, primitive aquatic animals, equipped with stinging tentacles and sac-shaped bodies.
- Acanthus. An edge of 1, 100 species of parasitic worms, whose bodies range between a few millimeters and 65 cm.
- Annelids Around 16, 700 species of worm-shaped invertebrate animals, segmented into rings.
- Arthropods. A gigantic edge of more than 1, 200, 000 described species of invertebrates equipped with chitin exoskeleton and articulated limbs, such as insects, crustaceans, arachnids and myropods. They are the largest edge of the kingdom.
- Braqui pods. Around 16, 000 species of marine animals endowed with two leaflets or shells, with which they protect their soft body and similar to mollusks. They are usually immobile.
- Bryozoans A set of up to 5, 700 species of marine animals (a few are freshwater) that have a fixed life and have a tentacular crown to capture food by filtering the water.
- Ropes Around 65, 000 species of vertebrate animals, possessing a dorsal cord of cells, of which most are fish, but also includes birds, mammals and reptiles.
- Echinoderms Marine and benthic animals, of which about 7, 000 current species are known, include sea urchins, starfish and the like.
- Mollusks Another of the great edges of the kingdom, includes 100, 000 living species of invertebrate animals, soft body and mainly aquatic habitat, among which are octopus, clams, slugs, etc.
- Nem todos. An edge of worms that covers more than 25, 000 species, commonly called round or cylindrical worms, and represent 90% of life in the oceanic relief.
- Platelmintos The so-called `` flat worms '', are about 20, 000 species of hermaphroditic animals from ohmedal aquatic environments, many of which lead a parasitic life.
It will be missing here to list many other edges of numerous animal species, whose differences can become very specific.
It can serve you: Taxonomy.
Importance of the animal kingdom
The animal kingdom is one of the most studied and the first to be formulated, since human interest in animals dates from ancient times . Not only as a source of food, or of usable raw materials, but also as a source of biological knowledge that allows us to answer fundamental questions about the origin of life, the dynamics of the living body or the maintenance of the ecological cycle that allows a diverse world, vast and beautiful.
Examples of the animal kingdom
Some simple examples of the animal kingdom are:
- Domestic animals: the dog, the cat, the hamster, the birds, the mice.
- Insects and arthropods, from spiders, scorpions and centipedes, to crabs, damp piglets, lobsters and the enormous diversity of insects: mosquitoes, flies, beetles, mantis, cockroaches, bees, etc.
- Marine animals such as fish, dolphins, sea lions, whales, sharks, mussels, sea urchins, starfish, but also simpler ones such as zooplankton, jellyfish, etc.
- The worms in their enormous variety: intestinal parasites, earthworms, crawling worms, etc.