To study nature, a series of taxonomic categories are used that divide the living beings in groups. Each of these categories groups beings that have some characteristics in common.
A traditional series of taxonomic categories is the following (from the most general to the most particular):
Domain – Kingdom – Phylum or division – Class – Order – Family – Genus – Species
That is to say that the kingdoms are very extensive subdivisions.
What are the Kingdoms?
- Animalia. Beings with the ability to move, without chloroplast or cell wall, with embryonic development. They are eukaryotic organisms.
- Plantae. Photosynthetic living beings, without the ability to move, with cell walls largely composed of cellulose. They are eukaryotic organisms.
- Fungi. Beings with cell walls made up largely of chitin. They are eukaryotic organisms.
- Protista. All eukaryotic organisms that do not meet the characteristics that would allow them to be classified within the three previous kingdoms. Eukaryotic cells are those that have the nucleus differentiated from the rest of the cell.
- Monera. Prokaryotic beings, that is, those whose cells do not have a differentiated nucleus.
Characteristics of the Animal Kingdom
The animal kingdom (Animalia) groups together a wide variety of organisms that meet various characteristics:
- Eukaryotic cells. The nucleus of these cells is separated from the cytoplasm by a cell membrane. In other words, the genetic information is separated from the cytoplasm.
- Heterotrophs. They feed on organic matter that comes from other living things.
- Multicellular. They are those that are made up of two or more cells. All animals are made up of millions of cells.
- Movement ability. Unlike other living beings (such as plants or fungi), animals have anatomical structures in their bodies that allow them to move around.
- Tissue. In animals, cells form organized structures called tissues. In them, the cells are all equal and regularly distributed. Their physiological behavior is coordinated. The cells of a tissue share the same embryonic origin.
- Cell walls without chloroplast. It is the substance that allows plants to carry out photosynthesis. Since animals do not have chloroplast, they must feed on other living things (heterotrophs)
- Embryonic development. From a single zygote (cell resulting from the union of a male gamete and a female gamete), embryonic development begins cell multiplication to form the entire organism, with its multiplicity of differentiated cells, tissues, organs and systems.
Examples of Animal Kingdom
- Human being (Homo Sapiens). Edge: cordate. Subphylum. Vertebrate. Class: mammal. Order: Primate.
- Ant (Formicidae). Phylum: arthropod. Subphylum: Hexapod. Class: insect. Order: hymenopteran.
- Eoperipatus totoro. Phylum: velvety worm. Class: udeonychopohora. Order: Euonychophora. Peripatidae family.
- Bee (anthophila). Phylum: arthropod. Class: insect. Order: hymenopteran.
- Domestic cat (felis silvestris catus). Edge: cordate. Subphylum: vertebrate. Class: mammal. Order: carnivore. Family. Feline.
- Elephant (elephantidae). Edge: cordate. Subphylum: vertebrate. Class: Mammal. Order: proboscidean.
- Crocodile (crocodylidae). Edge: cordate. Class: Sauropsido. Order: Crocodilia.
- Butterfly (lepidoptera). Phylum: arthropod. Class: insect. Order: Lepidoptera.
- Yellow clam (mactroid yellow desma). Phylum: mollusk. Class: bivalve. Order: veneroid.
- Salmon (psalm). Edge: cordate. Subphylum: verbrate. Order: salmoniformes.
- Oceanic dolphin (delphinidae). Edge: cordate. Class. Mammal. Order: cetacean.
- Ostrich (struthio camelus). Edge: cordate. Class: ave. Order: struthioniforme.
- Penguin. Edge: cordate. Class: Ave. Order: sphenisciforme.
- Boa. Edge: Cordado. Class: sauropsid. Order: squamata.
- Bat (chiropter). Edge: cordate. Class: mammal. Order: chiroptera.
- Earthworm (lumbrícido). Phylum: annelid. Class: clitellata. Order: haplotaxida.
Subdivision of the Animal Kingdom
The animal kingdom in turn is divided into large groups called phyla:
- Acanthocephala (Acanthocephalus). Parasitic worms (they get food from other live animals). They have a “head” with thorns.
- Acoelomorpha (Acelomorphs). Cellophane worms (solid, without cavities) that do not have a digestive tract.
- Annelida (Annelids). Coelominated worms (with cavities) that have the body segmented into rings.
- Arthropoda (arthropods). They have a chitin exoskeleton (carapace or similar structure) and jointed legs
- Brachiopoda (Brachiopods). They have a loptophore, which is a rounded organ with tentacles that surrounds the mouth. They also have a shell with two valves.
- Bryozoa (Bryozoans). They have a loptophore and anus outside the tentacular crown.
- Chordata (Chordate). They have a dorsal chord or spine, also called the notochord. They can lose it after the embryonic stage.
- Cnidaria (Cnidarians). Diblastic animals (complete embryonic development without mesoderm) that have cnidoblasts (cells that secrete defense substances)
- Ctenophora (Ctenophores). Diblastic animals with coloblasts (cells to trap food)
- Cycliophora (Cyclophores). Pseudocoelomed animals (animals with a general cavity of non-mesodermal origin) with a circular mouth surrounded by cilia (thin, hair-like appendages)
- Echinodermata (Echinoderms). Animals with “skin with thorns”. They have pentarradiate symmetry (central symmetry) and an external skeleton made up of calcareous pieces.
- Echiura (Equiuroideos). Marine worms with proboscis and “thorn tail”.
- Entoprocta (entoproctos). Loptophores with anus included in the tentacular crown (inner anus)
- Gastrotrichia (gastrotricks). Pseudocoelomed animals, with spikes and two adhesive caudal tubes.
- Gnathostomulida (gnatostomúlidos). Animals with characteristic jaws that distinguish them from other animals.
- Hemchordata (hemichordates). Deuterostomous animals (animals that in their embryonic state develop the anus before the mouth), with pharyngeal fissures and stomocord (a kind of spinal column where the weight of the body is supported).
- Kinorhyncha (quinorhincs). Pseudocoelomed animals with retractable head and segmented body.
- Loricifera (Lorociferous). Pseudocoelomed animals covered with a protective coating.
- Micrognathozoa (micrognatozoa). Pseudocoelomates with complex jaws and an extendable thorax.
- Mollusca (mollusks). Soft-bodied animals, mouths with radula and covered by a shell.
- Myxozoa (myxozoa). Microscopic parasites. They have polar capsules that secrete defense substances.
- Nematoda (nematodes). Pseudocoelomed worms that have a chitin cuticle.
- Nematomorpha (nematomorphs). Parasitic worms similar to nematodes.
- Nemerte (Nemertinos). Cellophane worms (no cavity, solid body) with extendable proboscis.
- Onychophora (velvety worms). Worms with legs that end in chitin nails.
- Orthonectide (orthonrectids). Parasites with cilia (hair-like appendages)
- Phoronida (phoronids). Tube-shaped worms and U-shaped intestine.
- Placozoa (placozoans): Crawling animals.
- Platyhelminthes (flatworms). Worms with cilia, without anus. Many of them are parasites.
- Pogonophora (pogonophos). Tube-shaped animals with retractable heads.
- Porifera (sponges), Parazoans (animals without muscles, nerves or internal organs), with inhalant pores in the body, without defined symmetry.
- Priapulida (priapulids). Pseudocoelomed worms with an extendable proboscis surrounded by papillae.
- Rhombozoa (rhombozoa). Parasites made up of few cells.
- Rotifera (rotifers). Pseudocoelomates with a crown of cilia.
- Sipuncula (sipuncúlidos). Coelominated worms with mouths surrounded by tentacles.
- Tardigrada (water bears). Segmented trunk, with eight clawed legs or suction cups.
- Xenacoelomorpha (xenoturbelids). Deuterostomous worms with cilia.