chordates (phylum chordata) tunicates/sea squirts (urochordata) lancelets (cephalochordata)

Chordates (Phylum Chordata)

Tunicates/Sea squirts (Urochordata)

Lancelets (Cephalochordata)

Vertebrates (Craniata - formerly vertebrata)

A. Characteristics 1. Notochord a. slender rod - provides axial support 2. Pharyngeal gill slits a. feeding in “primitive” chordates, became gills 3. Dorsal Hollow Nerve Cord (DHNC) a. fluid filled central canal above notochord b. solid and ventral in other invertebrates 4. Postanal Tail

Notochord

Pharyngeal Slits

Dorsal, Hollow Nerve Cord

Postanal Tail

B. Tunicates (Subphylum Urochordata) 1. Sessile Marine animals 2. 2 life stages a. larval stage has chordate traits

C. The lancelets (Subphylum Cephalochordata) 1. small (<5cm), fusiform, Marine organisms 2. Paedomorphosis a. juvenile morph is retained in reproductive adult b. retained larval form of Urochordates in reproductive adults

Urochordate Larva Lancelet Adult

C. Vertebrates 1. Subphylum Craniata a. formerly Vertebrata

Phylogeny from

2. Vertebral Column a. Centrum

- Bony vertebral column i. replaces notochord

a. Neural Arch - encircles nerve cord- forms neural canal- some vertebrates lack vertebrae i. Hagfish-strengthend notochord

3. Cranium a. surrounds anterior brain

- bone or cartilage

Vertebra

Cranium

4. Jawless Fishes (Superclass Agnatha) a. Hagfish (Class Myxini)

- conatin most primitive characters - No vertebrae b. Lampreys (Class Cephalaspidomorphi)

- Cartilagenous vertebral plates - Parasitic on other vertebrates

Hagfish

5. Jawed Fishes (Superclass Gnathostoma) a. Jaws b. 2 sets of paired fins (Yaw, Pitch, roll)

Modern Fishes

Jawless Ancestors

c. Cartilaginous fishes (Class Chondrichtyes)

- Sharks and Rays - Cartilage skeleton - Multiple gill slits - Oil filled liver for buoyancy

i. Also hydrodynamic lift

- Reproduction i. Oviparous - lay eggs ii. Ovoviviparous - retain eggs internally until hatching iii. Viviparous - live bearing, nourishment from mother

d. Bony Fishes (Class Osteichthyes)

- Operculum - bony structure covering gills - swim bladder i. burp/gulp - connected to stomach - primitive ii. gas exchange - connected to blood vessels - derived

- Ray-finned fishes (Actinopterygii)

i. Extremely diverse ii. most of the fishes you know

- Lobe-finned fishes (Sarcopterygii)

i. Lungfish Live in shallow, fresh water Rely on lungs during dry season ii. Coelocanth Bottom dweller (off coast of Africa)

e. Transition to Land

f. Amphibians (Class Amphibia)

- Salamanders, toads, frogs, caecillians -Moist skin i. adapted for cutaneous respiration - Oviparous i. Undergo metamorphosis

g. Amniotes - Have amniotic egg i. shell that retains water - Can lay eggs in dry environments

h. Turtles (Anapsids) - Shell - no temporal fenestra (anapsid) - oviparous

i. Snakes and Lizards (Lepidosaurs) - Diapsid skull i. two fenestra (holes in temple) - Cranial kinesis (skull flexion) - scales

j. Archosaurs - Crocodilians, Pterosaurs, Dinosaurs, Birds - Diapsid skull - Antorbital fenestra Archosaurs

k. Birds (Class Aves)

- Feathers i. Rachis and Barbs

Rachis

BarbRachis

Barbs

- Bones (hollow, cross struts)- Keeled Sternum- Furcula (Wish bone)

- Homeotherm i. constant body temperature ii. endothermy

Bird in flight

KeeledSternum

Furcula

Flightless birds

- Bill i. No teeth ii. Light keratin beak

6. Class Mammalia - Mammals

1. Synapsid skull a. 1 temporal opening

2. Hair - keratinized filaments

3. Mammary glands a. produce milk to nourish young b. derived from sweat glands

- Heterodont dentition i. incisors - snipping ii. canines - tearing, grasping iii. cheek teeth

- premolars - crunching- molars grinding or slicing

- Limb position i. ventral - positioned under body

- differs from lateral position in ancestors- Endothermy/Homeothermy

- Monotremes - oviparous

- Marsupials i. primitive placenta ii. altricial young

- Eutherian mammals i. derived/advanced placenta ii. precocial young iii. most familiar mammals