Formation of the brain is quite a complex process.
It begins with a thickening of ectoderm (the outer layer of cells) above the notochord (which is a rod-shaped aggregate of cells that marks the future location of the spine). This thickened ectoderm forms the neural plate.
The sides of the neural plate fold up and eventually fuse - becoming the neural tube. The cells lining this tube are known as the neuroepithelium and produce all the future neurons.
The rostral (towards the head/nose) end of this neural tube forms the brain, and the rest of the tube forms the spinal cord.
The end of this tube which will become the brain begins to fold and expand. This forms three regions - prosencephalon (forebrain), mesencephalon (midbrain) and rhombencephalon (hindbrain). The most rostral end divides laterally to form the two lateral hemispheres of the cerebellum.
brain
There isn't a "popular name" for them. The most familiar chordates are the vertebrates, but not all chordates are vertebrates (tunicates, for example, are chordates).
lancelets
Chordates are that group of animals having some form of a spinal column (which include the vertebrates).
The Cranium
adult tunicate
Vertebrates are a subgroup of the chordates, meaning that all vertebrates are chordates, but not all chordates are vertebrates. Vertebrates are distinguished from other chordates by having backbones or spinal columns.All vertebrates have muscular systems that mostly consist of paired masses, as well as a central nervous system which is partly located inside the backbone (if one is present). The defining characteristic of a vertebrate is considered the backbone or spinal cord, a brain case, and an internal skeleton, but the latter is not true for lampreys, and the former is arguably present in some other chordates. Rather, all vertebrates are most easily distinguished from all other chordates by having a clearly identifiable head. Sensory organs--especially eyes--are concentrated at the foreend of the body, and there is pronounced cephalization.
Yes, most chordates are vertebrates.
Well, no they don't... There's a group of chordates called Agnatha which basically contains all the jawless chordates. And there are obviously limbless chordates present, the fishes and the snakes being the most well-known of the examples...
because
bilateral symmetry
The four specific characteristics of chordates are that they have a notochord, hollow nerve cord near the notochord, pharyngeal pouches, and an endostyle. Many of these characteristics disappear in invertebrate chordates when they reach adulthood. Most vertebrate chordates retain all four features, such as humans.