We explain what invertebrate animals are and how these animals are classified. Also, examples of invertebrates.
What are invertebrate animals?
It is known as invertebrate animals to the group of species in the animal kingdom that do not have a notochord or dorsal chord, nor a vertebral column, nor an articulated internal skeleton. In this group are found 95% of the known living species, between 1.7 and 1.8 million species (2005 figures).
Invertebrates also tend to be smaller in size, compared to large terrestrial or aquatic vertebrates, and although lack an articulated skeleton often have an exoskeleton (like insects) or shells and shells made of resistant substances (like mollusks).
This is not a homogeneous group by any means: since the beginning of the term “invertebrate” (from the French animaux sans vertebresanimals without vertebrae), their creator, The naturalist Jean-Baptiste Lamarck subdivided them into ten different classes: mollusks, cirripeds, annelids, crabs, spiders, insects, worms, echinoderms, polyps and infusoria. This classification is no longer used, of course.
The group of invertebrates has been difficult to classify and study, given their small size and the diversity of environments they inhabit. In the current classification of zoology, it is estimated that the group is made up of animals from the following phyla:
- Arthropods. Equipped with an exoskeleton and articulated limbs, like insects, arachnids, crustaceans and myriapods.
- Molluscs. Soft and unsegmented body, often covered with shell or carapace to defend it.
- Porifera. That is, marine sponges, with bodies endowed with radial symmetry.
- Cnidarians. Simple aquatic animals, such as corals and jellyfish.
- echinoderms. Mostly marine, like hedgehogs and starfish.
- Platyhelminthes. That is, flatworms (in some cases parasites).
- Nematodes Or cylindrical worms.
- Annelids. Or earthworms and leeches.
See also: Aquatic ecosystem
Examples of invertebrate animals
Some common examples of invertebrate fauna may be the following:
- common insects. Like cockroaches, butterflies, moths, beetles, flies, mosquitoes, ants, termites, etc.
- Venomous arachnids Like most spiders, scorpions or scorpions, centipedes.
- Marine crustaceans. Like lobsters, shrimp, prawns and sea roaches.
- Marine mollusks. Like octopus, mussels (and other bivalves), squid, etc.
- Parasitic flatworms. Such as the tapeworm, the hydatid worm or the wide fish worm.
- The cnidarians. Like sea anemones, jellyfish, corals and polyps.
- The echinoderms. Such as starfish, sea urchin, sea lilies, sea cucumbers or sea daisies.
- Cylindrical worms. Some parasites like ascaris lumbricoides or the toxocara canisand others of free and aquatic life.
