VERTEBRATESKingdom – ANIMALIA
Phylum – CHORDATA (means “cord”)Subphylum – VERTEBRATA (means “jointed backbone”)
I. Evolution of Vertebrates:
Invertebrate Ancestors
AmphibiansFish
Reptiles
Birds
Mammals
II. Characteristics of ALL VertebratesA. Hollow nerve cordB. Notochord – in embryos; in most
vertebrates is replaced by a backbone that protects nerve cord & allows for greater flexibility
C. Postanal Tail – extension of vertebrae in some vertebrates
D. Bilateral SymmetryE. Endoskeleton
F. Coelom – a body cavityG. Closed Circulatory System – blood
flows through vessels to/from heart
H. Complex Brain, Sense Organs & Efficient Respiratory
Systems
Chapter 28.1-2 – Fishes and Amphibians I. Characteristics of ALL Fish
A. Gills – respiratory structures made up of
feathery gill filaments w/ tiny blood vessels
1. Fish takes in water thru mouth
2. water w/ dissolved O2 (not from H2O) passes
countercurrent to blood flow in the
gill’s capillaries
B. 2-chambered Heart: slow blood flow
1. 1 chamber receives deoxygenated blood from the fish’s tissues
2. Other chamber pumps blood tocapillaries in gills, where
O2 is picked up & CO2 is dropped off
C. Sexual Reproduction – w/ egg & sperm
1. can be released directly into water
2. can be deposited on plants D. Paired Fins – (ray or lobe) fan-shaped
membranes made of bone for balance, swimming, & steering
1. Lobed fins foreshadowed the development of limbs for
movement on land & wings for flying (p. 831)
E. Developed Sensory Systems
1. Lateral Line – cartilage & bony fish have this fluid-filled canal line to
sense vibration changes in the environment
2. Eyes – allow fish to see objects & differences in light and dark
3. Sense of Smell – detect chemicals
Lateral line system
Swim/Air bladder
Scales
Gills
Fins
Kidney
Urinary bladder
Reproductive organ
Stomach
Intestine
Liver
Heart
II. Diversity of Fish (more species of fish than all other vertebrates combined)
A. Superclass AGNATHA – “without jaws”
Class MYXINI – hagfish Class
CEPHALASPIDOMORPHI – lampreys
1. Jawless, cartilage skeleton, no scales, internal fertilization
2. Lampreys use a sucker to attach & drink dying fish’s blood, teeth scrape flesh away
B. Class CHONDRICHTHYES – “cartilage”
sharks, skates, rays
1. Predators living on/near ocean floor
2. Jaws, cartilage skeleton, scales, paired fins, internal
fertilizationa. Skates deposit fertilized
eggs on ocean floor (mermaid purse)
b. Some sharks & rays carry young inside their
bodies