BIO 131 - Chordates

What are the 4 chordate characteristics?

Notochord, dorsal hollow nerve cord, pharyngeal slits, post-anal tail

What is the function of the notochord?

Flexible support structure

What does the dorsal hollow nerve cord develop into in vertebrates?

Brain and spinal cord

What are pharyngeal slits used for?

Feeding (early) and gas exchange

What is the post-anal tail used for?

Locomotion (Movement)

What are the invertebrate chordates?

Cephalochordata and Urochordata

How do we know invertebrate chordates are chordates?

They possess all 4 chordate traits (at least in larval stage)

What is the common name for Cephalochordata?

Lancelets

What is the common name for Urochordata?

Tunicates (and salps)

Which invertebrate chordate retains all chordate traits as an adult?

Lancelets (Cephalochordata)

Which invertebrate chordate loses most chordate traits as an adult?

Tunicates (Urochordata)

When did chordates first appear?

Cambrian period (~520 million years ago)

What are key evolutionary trends in vertebrates?

Increased cephalization, vertebral column, jaws, limbs

What major group do jawed vertebrates give rise to?

Tetrapods

What defines Subphylum Vertebrata?

Vertebral column (backbone)

What structure replaces the notochord in vertebrates?

Vertebral column

What are the major vertebrate groups?

Jawless fishes, jawed fishes, tetrapods

What are jawless fishes called?

Cyclostomes

Which animals are cyclostomes?

Hagfish and lampreys

Key trait: no jaws + eel-like body = ?

Cyclostome

Which cyclostome produces slime?

Hagfish

Which cyclostome is parasitic with a sucking mouth?

Lamprey

What is Conodontia known for?

First vertebrates with mineralized elements (early “bones/teeth”)

What are jawed vertebrates called?

Gnathostomes

 What major evolutionary feature defines gnathostomes?

Jaws

What do gnathostomes include?

Fish + tetrapods

What are the two major fish categories?

Jawless and jawed fishes

What are the main groups of jawed fishes?

Cartilaginous fishes (Chondrichthyes) and bony fishes (Osteichthyes)

Key trait: skeleton made of cartilage = ?

Cartilaginous fish (sharks, rays)

Key trait: skeleton made of bone = ?

Bony fish

What are important morphological traits of fishes?

Gills, fins, scales, lateral line system

What is the function of gills?

Gas exchange

What is the lateral line used for?

Detecting vibrations in water

Why are fish not monophyletic?

They do not include all descendants (tetrapods are excluded)

Why are humans considered “weird fish”?

We evolved from lobe-finned fish ancestors

Which fish group gave rise to tetrapods?

Lobe-finned fishes

Key trait: fleshy fins with bones = ?

Lobe-finned fish

Key trait: thin fins supported by flexible rays = ?

Ray-finned fish

Which fish group includes the vast majority of modern fish species?

Ray-finned fishes

What is NOT considered a dinosaur?

Flying reptiles (pterosaurs) and marine reptiles (like plesiosaurs)

Why are birds more closely related to crocodiles than to lizards?

Both birds and crocodiles are part of Archosauria

How are birds and dinosaurs related?

Birds evolved from theropod dinosaurs

What are the two major divisions of tetrapods?

Anamniotes and amniotes

What are anamniotes?

Tetrapods that lack an amniotic egg; require water for reproduction

What are amniotes?

Tetrapods with an amniotic egg, allowing reproduction on land

Which came first: anamniotes or amniotes?

Anamniotes

What is Urodela?

Salamanders (anamniotes) with tails and elongated bodies

What are the main groups of amniotes?

Reptiles (including birds) and Mammals

What are the main groups of anamniotes?

Anura, Urodela, and Gymphiona

What are mammal subgroups?

Monotremes, Marsupials, and Placentals

What are major reptile subgroups?

Testudines, Lepidosauria, and Archosauria