Answer: With the development of powerful microscopes, scientists discovered many single-celled organisms that didn't fit into any of Linnaeus' kingdoms. As a result, a new taxon, called the domain, was added to the classification system.
Explanation:
Chordates (phylum Chordata) are animals which are either vertebrates or one of several closely related invertebrates. They are united by having, for at least some period of their life cycle, a notochord, a HOLLOW DORSAL NERVE CORD
two adaptions would be hibernation and migration
Mutualism. e.g. oxpecker and zebra
commensalism. e.g. remora fish and sharks
parasitism. e.g. tapeworms and cow
