Introduction to Chordates

Vertebrate

Classification of organisms that share similar derived characteristics such as a notochord and a dorsal, hollow nerve cord.

Notocord

A flexible rod that provides skeletal support in chordates.

Genealogy

The study of the ancestral relations and evolutionary history of groups of organisms.

Gnathostome

Jawed vertebrates that evolved from early chordates.

Agnathan

Jawless vertebrates that include hagfish and lampreys.

Pharyngeal slits

Openings in the throat region of chordate embryos that function in feeding and gas exchange.

Tetrapods

Vertebrates that have four limbs, including amphibians, reptiles, birds, and mammals.

Amniotes

A group of tetrapods that includes reptiles, birds, and mammals characterized by the presence of amniotic eggs.

Cladistics

A method of classification based on the common ancestry and evolutionary relationships of organisms.

Mass extinction

A significant and rapid decrease in the variety and abundance of a large number of species in a relatively short time.

Swim bladder

An internal gas-filled organ that helps bony fish maintain buoyancy.

Lobefinned fish

A group of bony fish with fleshy, lobed fins, considered ancestral to tetrapods.

Eustachian tube

A canal that connects the middle ear to the nasopharynx, aiding in equalizing ear pressure.

Neural tube

The embryonic precursor of the central nervous system that develops from the dorsal ectoderm.

Hemichordate

A phylum of marine animals related to chordates, characterized by a body plan with a proboscis, collar, and trunk.

Lateral line system

A sensory system found in fish and some amphibians that detects water movements and vibrations.

Oxygen Content

The concentration of oxygen in a given medium, crucial for respiratory efficiency in aquatic vs terrestrial animals.

Endostyle

A glandular structure in chordates that secretes mucus, contributing to feeding and possibly homologous to the thyroid gland.

Paleozoic era

A geological era lasting from about 541 to 252 million years ago, marked by the emergence of vertebrates.

Mesozoic era

The era from about 252 to 66 million years ago, characterized by the dominance of dinosaurs.

Cenozoic era

The current geological era, beginning about 66 million years ago, known for the diversification of mammals and birds.

Chordate Classification

The hierarchical system categorizing animals with a notochord, including subphyla Urochordata and Cephalochordata.

Fossil Records

Preserved remains or traces of organisms from the past, providing insight into evolutionary history.

Neuron

The basic working unit of the nervous system, responsible for transmitting information throughout the body.

Cartilaginous skeleton

A skeleton made primarily of cartilage as seen in classes like Chondrichthyes.

Anadromous

Species, like salmon, that migrate from saltwater to freshwater for spawning.

Phylogenetic systematics

The study of the evolutionary relationships among biological entities.

Species diversity

The variety of species present in an ecological community.