We explain what invertebrate animals are and how these animals are classified. Also, examples of invertebrates.
What are invertebrate animals?
Invertebrate animals are known as all the species of the animal Kingdom they do not possess a notochord or dorsal chord, nor a vertebral column, nor an articulated internal skeleton. In this set are 95% of the species known living, between 1.7 and 1.8 million species (2005 figures).
Invertebrates are also usually smaller, in comparison with the greats vertebrates terrestrial or aquatic, and although they lack an articulated skeleton, they often have exoskeletons (like insects) or shells and shells of resistant substances (like molluscs).
This is not a homogeneous group, far from it: since the beginning of the term “invertebrate” (from the French animals sans vertebrae, animals without vertebrae), their creator, the naturalist Jean-Baptiste Lamarck, he subdivided them into ten distinct classes: molluscs, barnacles, 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 the zoology, it is estimated that the group is composed of animals of the following phyla:
- arthropods. Equipped with an exoskeleton and articulated limbs, like insects, arachnids, crustaceans and myriapods.
- Molluscs.Soft-bodied and unsegmented, often covered with a 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, such as sea urchins and starfish.
- Flatworms. That is, flatworms (in some cases parasites).
- nematodes. Or roundworms.
- Annelids. Or earthworms and leeches.
examples of invertebrate animals
Some common examples of invertebrate fauna can be the following:
- Common insects. Like cockroaches, butterflies, moths, beetles, flies, mosquitoes, ants, termites, etc.
- The poisonous arachnids. Like most spiders, scorpions or scorpions, centipedes.
- marine crustaceans. Like lobsters, shrimp, prawns and sea roaches.
- Marine molluscs. Like octopus, mussels (and other bivalves), squid, etc.
- Parasitic flatworms. Like the tapeworm, the hydatid worm or the wide worm of the fish.
- the cnidarians. Like sea anemones, jellyfish, corals and polyps.
- the echinoderms. Like starfish, sea urchins, sea lilies, sea cucumbers or sea daisies.
- cylindrical worms. Some parasites like ascaris lumbricoides or the toxocara canis, and others of free and aquatic life.