Short answers, pulled from the story.
Zoology is the scientific study of animals. Its studies include the structure, embryology, classification, habits, and distribution of all animals, both living and extinct, and how they interact with their ecosystems. It is one of the primary branches of biology.
The formal study of zoology can be said to have originated with Aristotle in the fourth century BC. He viewed animals as living organisms, studied their structure and development, and divided them into animals with blood, equivalent to vertebrates, and animals without blood, the invertebrates.
About 1.5 million species of animal have been described. It has been estimated that as many as 8 million animal species may exist.
Zoology uses Linnaean taxonomy, which includes ranks and binomial nomenclature ordered as domain, kingdom, phylum, class, order, family, genus, and species. The scientific name combines genus and species, as in Homo sapiens, with the genus capitalized and the specific epithet in lowercase.
Zoology divides into vertebrate zoology, covering fish, amphibians, reptiles, birds, and mammals, and invertebrate zoology, covering sponges, echinoderms, worms, molluscs, arthropods, and other phyla. It also includes branches such as physiology, developmental biology, evolutionary biology, ethology, biogeography, and molecular biology.
In 1953, Francis Crick and James Watson described the structure of the DNA molecule, opening the realm of molecular biology. DNA sequencing transformed systematics by elucidating the degrees of affinity between different organisms.