Unit 4 - Vertebrates

chpater 29

Notochord

flexible, rod-like structure made of mesoderm that provides support and serves as a site for muscle attachment in chordates. It is present in all chordate embryos and is replaced by the vertical column in most vertebrates

Hollow dorsal nerve chord

tube of nervous tissue derives from ectoderm that runs along the back (dorsal side) of chordates and develops into the brain and spinal cord

Pharyngeal slits

openings in the pharynx that connect the internal pharynx to the external environment.

In aquatic vertebrates, they allow water to exit after feeding and develop into gills or jaw structures, while in terrestrial environments they develop into structures like the ear, tonsils, and thymus.

Post-anal tail

muscular and skeletal extension of the body that extends beyond the anus in chordates.

• locomotion & balance

Endostyle / Thyroid gland

mucus producing structure on the floor of the pharynx that helps with feeding and produces similar to thyroid hormones.

• develops into thyroid gland in most vertebrates

Cephalochordata

primitive chordates (lancelets) in which adults retain all 5 key chordate characteristics: notochord, dorsal hollow nerve chord, pharyngeal slits, post anal tail, and endostyle/thyroid gland.

Urochordata

chordates (tunicates/sea squirts) in which larvae possess all 5 chordate characteristics, but adults retain only pharyngeal slits and the endostyle

cranium

bony, cartilaginous, ligamentous structure that surrounds and protects the brain and includes the jaw and facial structures in vertebrates

Agnathostomes

jawless vertebrates

Gnathostomes

jawed vertebrates

• fish

• tetrapods

Tetrapods

vertebrates with 4 limbs, including amphibians, reptiles, birds and mammals

Amniotes

tetrapods whose embryos develop into eggs with extraembryonic membranes, allowing reproduction on land.

• reptiles, birds, mammals

double circuit

circulatory system in which blood passes through the heart twice during one complete trip through the body: once to go to the lungs/respiratory organs and once to go to the rest of the body

Caudata

order of amphibians that includes salamanders and axolotls. They’re considered the most ancestral amphibians, and many respire through their skin or external gills rather than lungs.

Anura

order of amphibians that includes frogs and toads. They are diverse, typically have strong hinds limbs for jumping, possess lungs and eardrums, and are capable of vocalization

Gymnophiona

also known as Apoda, an order of amphibians that includes caecilian. They are limbless, burrowing amphibians with a derived trait of no limbs.

Amniotic egg

specialized egg with protective membranes and a shell that allows embryos to develop on land by providing nourishment, protection, and a controlled internal environment

Albumen fluid

protein rich fluid in an egg that surrounds the embryo providing protection and a source of nutrients

Chorion

flexible membrane surrounding embryo and yolk sac

Yolk sac

membrane that surrounds the yolk and helps transfer nutrients from the yolk to the developing embryo

Yolk

nutrient rich material in an egg that provides food for the developing embryo

Amnion

fluid filled cavity that surrounds the embryo

Allantois

membrane that stores waste and facilitates gas change for the embryo

Homeotherm

organism that maintains a constant internal body temperature regardless of changes in the external environment

Cloaca

single body opening in birds where digestive urinary and reproductive systems all empty, allowing waste and reproductive materials to exit the body

Countercurrent respiratory system

system in which air flows in one direction and blood flows in the opposite direction, maximizing gas exchange efficiency

Sebaceous gland

mammalian skin glands that secrete liquids (oils) to waterproof and protect the skin and hair

Eccrine gland

sweat glands that produce perspiration, helping regulate body temperature through cooling

Apocrine gland

scent producing glands that release chemical signals used in communication

Heterodont teeth

specialized teeth of different shapes and functions (such as incisors, canines, and molars) used for various types of food processing

Adductor muscle

jaw muscle that allows for up-and-down and side-to-side movement, enabling chewing

Sinoatrial node

specialized group of cells in the heart that acts as the natural peacemaker, generating electrical signals that control the heart’s rhythmic beating

Turbinate bones

structure in the naval cavity that increase surface area to warm, humidity, and filter inhaled air before it reaches the lungs

Pulmonary system

respiratory system that moves air into and out of the lungs, allowing gas exchange through a branching network of airways from the nasal cavity to the bronchioles

Trachea

windpipe that connects the pharynx and larynx to the lungs, funneling air into the bronchi and out of the respiratory system. It is supported by cartilage and lined with mucus and cilia.

Primary bronchi

2 main branches of the trachea that lead directly into each lung and distribute air into smaller airway branches

Secondary bronchi

branches of the primary bronchi that further divide within each lung to distribute air into smaller airways called tertiary bronchi

Monotremes

mammals that lay leathery eggs but still produce milk through mammary glands to nurse their young.

• examples: platypuses and echidnidas

Marsupials

mammals with a short gestation period in the uterus; their young are born underdeveloped and completely develop in a pouch with mammary glands.

• examples: kangaroo, koala, opossums

Placentals

mammals in which a placenta connects the fetus to the mother, allowing exchange of gases, nutrients, wastes during long gestation. Young are more fully developed at birth and are nourished by milk after birth

• examples: horses, tigers, humans