Question

Which ones of the following animals are invertebrates?
Housefly, silverfish, trout, jellyfish, whale, penguin, lizard and sponge.

Answer 1

Invertebrates are animals without a backbone or bony skeleton. They range in size from microscopic mites and almost invisible flies to giant squid with soccer-ball-size eyes.

Complete answer:
The invertebrates include a large number of diverse types of animals including all but one of the phyla of the animal kingdom and even some of the branches of that one phylum (Chordata). The classification of this assemblage is therefore of cardinal importance in the study of the invertebrates. These differences are chiefly of two sorts: first, the use of different names for the same group, and second, the placing of the same group in different systematic categories, as, for example, the designation of a group as a class by one writer, but as an order by another. The notochord is the defining structure of the chordates, and has essential roles in vertebrate development. It serves as a source of midline signals that pattern surrounding tissues and as a major skeletal element of the developing embryo. Genetic and embryological studies over the past decade have informed us about the development and function of the notochord. Sponge, housefly, starfish and jellyfish are invertebrates. Invertebrates are those animals which do not possess a notochord.

Note: An invertebrate is an animal that does not have a backbone. Ninety-seven percent of all animal species are invertebrates. Insects, annelids, mollusks, echinoderms, protozoa, crustaceans, and arachnids are all invertebrates.