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

C. Class OSTEICHTHYES – means “bony”

walleye, sturgeon, bass, trout, perch, etc.

1. Jaws, bony

skeleton, scales, paired fins

2. Air/Swim bladder – depth is changed by

adjusting amount of gas

3. Most do external fertilization

called “spawning”