Phylum Chordata

PHYLUM CHORDATA Characteristics of Chordates: all chordates have 4 characteristics in common at some point in their life cycle: dorsal, hollow nerve tube: in most adult chordates, the posterior part develops into a spinal cord and the anterior part develops into a brain notochord: firm flexible tube just below the nerve tube(backbone in vertebrates), where muscles can attach gill slits: paired openings along the pharynx which functions in filter feeding post-anal tail: at some point during development, a tail reaches beyond the anus There are actually 3 subphylums of chordates, 2 of which are invertebrates)

The Phylum Chordata Includes: Subphylum Cephalochordata (= lancelets) Subphylum Urochordata (= tunicates) Subphylum vertebrata: Class Agnatha - jawless fish (hagfish) Class Amphibia – amphibians like frogs Class Aves – birds Class Chondrichthyes - cartilaginous fish (sharks) Class Osteichthyes - bony fish Class Reptilia – reptiles like lizards Class Mammalia - mammals

Tunicates (Subphylum Urochordata) About 3000 living species Also called sea squirts; live in shallow marine waters Adults are sessile and have lost notochord and postanal tail Filter feeders Reproduce sexually

Lancelets (Subphylum Cephalochordata) Only about 25 living species Live in shallow ocean waters Filter feeders

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Characteristics of All Vertebrates 1. have a backbone, which surrounds spinal cord, is made up of bony segments called vertebrae 2. an endoskeleton which has two main parts: i. Axial Skeleton: made up of the vertebral column, skull & rib cage - supports body and protects spinal column, brain & other internal organs ii) Appendicular Skeleton: made of the appendage bones and wide flattened girdles to which they are attached - is attached to axial skeleton - e.g. arms, legs

3. Well developed brain & sensory organs 4 3. Well developed brain & sensory organs 4. A closed circulatory system 5. Multi-chambered heart 6. Bilateral symmetry 7. Coelomates 8. Efficient respiratory systems 9. Only phylum to have bones

FISHES Super Class Agnatha: Inhabit nearly every type of aquatic environment on Earth Can be grouped into 4 classes: Super Class Agnatha: 1. Class Myxini: hagfish 2. Class Cephalaspidomorphi: lampreys 3. Class Chondrichthyes: cartilaginous fish (ex. Sharks & rays) 4. Class Osteichythes: bony fish (ex. Swordfish, tuna, trout…)

Characteristics of All Fish 1. breathe using gills as a fish takes water in through its mouth, water passes over the gills & then out through slits at the side of the fish 2. have 2 chambered hearts One chamber receives oxygen-poor blood from the body tissues The other chamber pumps blood directly to the capillaries of the gills, where oxygen is picked up & carbon dioxide released 3. reproduce sexually Fertilization & development is external in MOST fishes Eggs & sperm can be released directly into the water, or deposited in more protected areas 4. highly developed sensory systems Have eyes that allow them to see objects & contrasts between light & dark in the water, but the amount of vision varies among fishes

SUPER CLASS AGNATHA jawless fish lampreys & hagfish have smooth, scaleless skin & long cylindrical body Lampreys: most are parasites that hitch rides on their hosts, often killing its host as it sucks out its victim’s body fluids Hagfish: bottom dwellers that spend most of their time hiding in mud & sand scavenger that eats fish that are already dead or dying