Fish are aquatic vertebrates. They usually have gills, paired fins, a long body covered with scales, and tend to be cold-blooded. “Fish” is a term used to refer to lampreys, sharks, coelacanths and ray-finned fishes, but is not a taxonomic group, which is a clade or group containing a common ancestor and all its descendants.
All insects are part of the taxonomical phylum Arthropoda, and they are collectively referred to as arthropods. It is common to see this name misspelled as “anthropod,” but this is not the correct term. They can be found in nearly every environment on the planet, and they currently account for over half of all known living organisms in the world. They have undergone many cycles of evolution depending on the resources available to them.
The official mammal class is Mammalia. Animals that are considered mammals include warm-blooded vertebrates that have hair or fur and whose babies drink milk. Unlike other animal types like birds and insects, all mammal babies drink milk that comes from their mother’s bodies. This is one of the key ways to know if an animal is a mammal.
The definition of an invertebrate is any animal that does not have a backbone or vertebral column. The most prolific and easily recognizable members of the invertebrate family are insects. It’s estimated that upwards of 30 million individual species of invertebrates may exist accounting for between 90-95 percent of all organisms on the planet.