Dogs belong to Chordata because during the dogs development the dog has a notochord and also it is a vertebrate which allows it to fall under phylum chordata.
A chordate is an animal of the phylum Chordata.
All chordates possess five synapomorphies, or primary characteristics, at some point during their larval or adulthood stages that distinguish them from all other taxa.
The phylum chordata includes all animals that share four characteristics, although they might each possess some of them at different stages of their development: a notochord, a dorsal nerve cord, pharyngeal slits, and a postanal tail.
Mammals are a group of vertebrates constituting the class Mammalia, characterized by the presence of mammary glands which in females produce milk for feeding their young, a neocortex, fur or hair, and three middle ear bones.
Dogs and cats are distinct species, incapable of producing offspring together because of the many differences in their genome.
At least, that's the traditional definition of a species, and it works—for the most part.
The dog or domestic dog is a domesticated descendant of the wolf, and is characterized by an upturning tail.
The dog is derived from an ancient, extinct wolf, and the modern wolf is the dog's nearest living relative.
A chordate is an animal of the phylum Chordata.
All chordates possess five synapomorphies, or primary characteristics, at some point during their larval or adulthood stages that distinguish them from all other taxa.
We can define chordate as follows: “The chordates are the class of animals that possess four anatomical features, namely (1) notochord, (2) dorsal nerve cord, (3) post-anal tail, and (4) pharyngeal slits, at least during some part of their development into maturity.”
Most species within the phylum Chordata are vertebrates, or animals with backbones (subphylum Vertebrata).
Examples of vertebrate chordates include fishes, amphibians, reptiles, birds, and mammals.
A modern human one species of mammal is a familiar example of a chordate.