Phylum Chordata and Subphylum Vertebrata Lecture Notes

Vocabulary flashcards covering the characteristics, classification, and biological functions of Phylum Chordata, with a focus on Agnatha, Chondrichthyes, and Osteichthyes.

Phylum Chordata

A group of diverse animals sharing four key characteristics: a notochord, dorsal hollow nerve cord, pharyngeal slits, and post-anal tail.

Notochord

A flexible rod-like structure that provides structural support in chordates.

Dorsal Hollow Nerve Cord

A characteristic chordate feature that develops into the central nervous system.

Triploblastic

An organization involving three germ layers: ectoderm, mesoderm, and endoderm.

Sub-phyla of Chordata

Phylum Chordata is divided into four groups: Hemichordata, Urochordata, Cephalochordata, and Vertebrata.

Vertebrata

A subphylum of animals characterized by the presence of a backbone or vertebral column which protects the spinal cord.

Class Agnatha

A group of jawless fish representing the earliest vertebrates, featuring cartilaginous skeletons and cylindrical bodies.

Myxini

The scientific name for hagfish, which are scavengers within the class Agnatha.

Petromyzontida

The scientific name for lampreys, which often exhibit a parasitic lifestyle using toothed, funnel-like mouths.

Ectothermic

Organisms, such as agnathans, that do not regulate their own body temperature and rely on the environment.

Nephrostomes

Specialized structures in agnathans that aid the kidneys in the filtration of metabolic waste.

Sinuses

Open spaces through which blood is distributed in agnathans, as they lack true capillaries.

Class Chondrichthyes

A class of cartilaginous fish that includes sharks, rays, and chimaeras, possessing skeletons made of cartilage instead of bone.

Placoid Scales

Minute, tough scales covering the skin of Chondrichthyes, providing protection.

Claspers

Structures found on the pelvic fins of male Chondrichthyes used for reproduction.

Spiracles

Small openings located behind the eyes in many Chondrichthyes that allow for the intake of oxygen-rich water even when the mouth is closed.

Rectal Glands

Specialized structures in Chondrichthyes located near the cloaca that help maintain osmotic balance by secreting concentrated salt solutions.

Ampullae of Lorenzini

Specialized electroreceptor organs in Chondrichthyes, particularly sharks, used to detect weak electric fields produced by other organisms.

Squalene

Liver oil used by Chondrichthyes to regulate buoyancy and maintain position in the water column.

Class Osteichthyes

The largest group of vertebrates, consisting of bony fish characterized by skeletons composed of bone.

Operculum

Bony plates covering the gill slits in bony fish that help actively pump water over the gills.

Swim Bladder

A gas-filled organ in many bony fish used to adjust buoyancy and conserve energy during vertical movement.

Lateral Line System

A row of sensory organs along the body of bony fish that detects changes in water pressure to help identify prey and predators.

Countercurrent Exchange

A specialized circulatory adaptation in bony fish, such as tuna ($Thunnus\,spp.$), that maximizes oxygen uptake.

Broadcast Spawning

A reproductive strategy where large quantities of eggs and sperm are released into the water for external fertilization.