Chordate Evolution - Where Did We Get Our Brains?

Vocabulary flashcards covering the phylogeny, classification, and key anatomical features of chordates and the evolution of the vertebrate brain.

Chordata

A phylum of animals characterized by four main features: a hollow dorsal nerve cord, pharyngeal slits, a notochord, and a post-anal tail.

Deuterostomes

A group of triploblastic animals (Bilatarians) where the blastopore develops into the anus.

Hollow dorsal nerve cord

A structure formed from the infolding of ectoderm that runs the length of the body and differentiates into the brain and spinal cord in vertebrates.

Pharyngeal slits

Openings that connect the pharynx with the external environment; used for filter feeding in early chordates and as gills in fishes.

Notochord

A flexible, rod-like structure made of large cells with turgid fluid-filled vacuoles and an outer sheath layer, which is replaced by the vertebral column in nearly all vertebrates.

Post-anal tail

A chordate characteristic consisting of a structure that extends beyond the anus.

Cephalochordata

A subphylum of chordates, also known as lancelets, that have no brain but use Hox genes to form a cranial bulb in the nerve cord.

Urochordata

A subphylum of chordates, including sea squirts and salps, characterized by a tadpole-like free-swimming larval form and a tunic-enclosed adult form.

Tunic

A body covering found in adult urochordates made of secreted protein and cellulose-like material.

Thaliacea

A class of urochordates (salps) that can produce huge swarms very quickly, reaching densities of up to $5000\,\text{individuals per m}^3$ through asexual reproduction.

Botryllus schlosseri

A colonial sea squirt used as a model for neurodegeneration due to its unique life cycle involving two distinct neurodegenerative pathways.

Vertebrata

A group of chordates characterized by a vertebral column, an endoskeleton, a distinct head with a neural crest, and a highly-differentiated brain.

Neural crest

A vertebrate feature associated with the development of a distinct head and paired sense organs for active foraging.

Hindbrain

An extension of the spinal cord in vertebrates that primarily coordinates motor reflexes and is centered in the cerebellum.

Midbrain

The part of the vertebrate brain primarily responsible for processing visual information.

Forebrain

The part of the vertebrate brain primarily responsible for processing olfactory information.

Cerebellum

A part of the hindbrain that increased in size as vertebrates moved onto land to allow for more complex coordination of movement.

Cerebrum

A brain region that increased significantly in mammals to process social behavior, communication, self-awareness, and sensory signals.