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Phylum Chordata

Characteristics

• All chordates possess a notochord.

• Long flexible rod between gut & nerve cord

• Runs most of length of animal

• Possess a dorsal, hollow, nerve cord

• Possess pharyngeal slits

• Muscular post-anal tail

Subphylum Urochordates

• Commonly called tunicates

• Sessile marine animals as adults - Motile as larva

• Larva possess a clear notochord which is less evident in adults

• Filter feed through use of siphon

Subphylum Cephalochordate

• Commonly known as lancelets

• Have all features of the ideal chordate

• Bury selves in sand, and filter-feed through mouth

Subphylum Vertebrata

• Seven extant classes

• First 3 commonly called fishes

• Remaining 4 called tetrapod’s (4 feet)

• All possess some form of segmented vertebra

Class Agnatha

• Commonly known as Jawless Fish

• Include hagfish & Lampreys

• Lack paired appendages

• Lack bony skeleton

• Lack jaws

• Usually have circular sucking mouthparts

• Lampreys parasitize other fish

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Class Chondrichthyes

• Include sharks & skates, & rays

• Very successful class

• Called cartilaginous fishes because skeleton is cartilage not bone

• Approx. 750 species

• Have paired appendages

• Many have acute senses

• Sharks have a lateral-line system

• Allows shark to detect water pressure changes

Class Osteichthyes

• Called Bony fish

• Most diverse of all fish

• Have skeleton made of bone

• Have Cycloid Scales

• Have paired fins

• Allowed evolution of 4 limbed amphibians (tetrapod’s)

• Possess scales for protection

• Have bony flap called operculum

• Allows water to be drawn over gills by fins

• Have Swim bladder

• Gas content can be manipulated allowing for changes in buoyancy

Class Amphibia

• First vertebrates to inhabit land

• Most are 4 limbed (tetrapod’s)

• Include frogs, salamanders & caecilians

• Have 3 chambered heart

• Have more complicated gas exchange organs (often a combination of lungs,

gills and skin)

Order Urodela

• Salamanders & Newts

• Urodela ("tailed ones" - Salamanders)

• More dependent on water

• Many species possess gills as adults

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Class Apoda

• "tail-less ones" - Frogs & toads

• Have more developed lungs than salamanders

• Lack a diaphragm & must “swallow” air

• Most diverse and common of amphibians.

• Toads are the first amphibians to evolve keratinized skin.

This waterproofs the skin preventing water loss

• Toads must still return to water to lay eggs.

• Caecilia "legless ones"

Reproduction and Metamorphosis

• Lack internal fertilization & amniotic eggs

• Reproduction must occur in H2O

• Most species undergo metamorphosis

• Larval stage (tadpole) is usually an aquatic herbivore

• Lacks legs, respiration is through gills

• Develops into tetrapod adult (usually carnivorous)

Class Reptilian

• Includes lizards, snakes, turtles, and crocodilians

• Over 7000 species

• Possess several advanced features over amphibians

• Most adaptations towards independence from H2O

• Possess scales containing keratin

• Keratin is a waterproofing protein which prevents water loss in an

organism

• Possess an amniotic egg.

• Prevents water loss of embryo. Allows for eggs to be laid on dry land

• Combined with internal fertilization, allows reptiles to reproduce

independently of water

• Reptiles are "cold blooded" or ectotherms

• Cannot internally regulate body temperatures

• Reptiles can regulate body temperatures behaviorally (e.g. Basking or

swimming)

• Nutritional requirements are lower than warm blooded animals

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Modern Reptiles

Order Chelonia (Turtles & Tortoises)

• Inhabit aquatic and terrestrial environment.

• Are herbivores, carnivores, and omnivores

• Characterized by possessing a hard-dorsal shell

• Made from bone, extensions of backbone and rib cage

Order Squamata

• Lizards & Snakes

• Most numerous & diverse of the reptiles

• Most relatively small Although monitors and their relatives can grow to 6'

in length

• Herbivores, carnivores & omnivores

• Most able to exhibit some form of hibernation

Order Crocodilian

• Crocodiles, Alligators, & Caimans

• Largest extant reptiles can grow to over 15’ and weigh over a ton

• Primarily aquatic they are true reptiles

• Inhabit warm, tropical climates

• Order most closely related to the dinosaurs

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Class Aves

• The birds

• Evolved from dinosaurs during Mesozoic era.

• Amniotic eggs and scales on legs remnants of reptilian origins

• Almost all adaptations of these animals are made for flight.

• Presence of feathers

• Made of keratin

• Can be used for insulation and flight

• Forelimbs developed into wings

• Honeycombed, light bone structure

• Feathers

• Beak Types

• Absence of some organs

• Females usually have 1 ovary

• Absence of teeth lighten head

• Replaced by gizzard in abdomen & beak

• Beak made of keratin

• Proven very adaptable structure, having a variety of shapes for differing

diets

Modern Birds

• Over 8600 species & 20 orders of birds

• Classified into 2 general groups

• Flightless species including ostrich, emus, & kiwis are known as ratites

o Lack sternal keel on breastbone

o Lack strong breast muscles needed for flight

• Other species capable of supporting flight called carinates

• 60% are "perching birds" called passeriforms

o Possess a sternal keel on breastbone

o Support strong breast muscles required for flight

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Class Mammalia

• Approx. 4500 species of mammals

• Evolved from mammal-like reptiles called therapsids in the Triassic period

• Diversified greatly following the extinction of dinosaurs

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Mammalian Characteristics

• Have Hair

• Made of keratin

• Aids in maintaining body temperature

• Endothermic

o Maintain body temperature internally

• Have efficient respiratory system including a diaphragm

• Efficient circulatory system with a 4-chambered heart

• Most possess placentas and give birth to live young

• Have mammary glands to produce milk for offspring

• All show parental care of offspring

• Have largest brains of all vertebrates

• Have differentiated teeth

• Unlike earlier vertebrates, several different teeth can exist in mammal

jaws

E.g. The molars & incisors in the human jaw

General Types of Mammals

Monotremes

• Early branch from reptilian line

• Include platypuses & echidnas (spiny anteaters)

• Only group to lay eggs (reptilian in structure)

• Have mammary glands to feed young

Marsupials

• Include opossums, kangaroos & koalas

• Mostly found in Australia & New Zealand

• Were isolated in these landmasses when the continents separated and did

not evolve li the same way placental mammals did

• Do not develop placentas

• Give birth to young very early

• Fetuses complete development in pouch called marsupium

• Mammary glands found in pouch nourish young until development is

complete

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Placental Mammals

• Complete embryonic development in uterus

• Joined to parent by organ called placenta

• Only "disposable" mammal organ

• Discarded following birth

• Exchanges gasses, nutrients & waste between mother and fetus