Lecture #10 - Kingdom Animalia: Vertebrate Phylogeny and Diversity

I. Phylum Chordata

A. Characteristics (Fig 34.1)

1. Notochord

2. Dorsal, hollow nerve cord

3. Pharyngeal slits

4. Muscular postnatal tail

B. Protochordata

1. Cephalochordata - Lancets (Fig 34.3)

a. Adults - chordate characteristics persist

2. Urochordata - Tunicates (Fig 34.2)

a. Larvae - have chordate characteristics

b. Adults - sessile filter feeders, lacking some chordate characteristics (no post anal tail,)

C. Vertebrata

1. Vertebrae - segmented cartilaginous or bony protection around the nerve cord (spinal cord)

2. Greater cephalization

a. Skeleton includes cranium and vertebral column

i. replaces notocord as main axis of body

ii. may be bone or cartilage

b. Anatomical adaptations which support greater mobility and activity - closed respiratory system

II. Chordate/Vertebrate Phylogeny (modify Fig 34.6)

A. Split #1 - bearing or lacking vertebrae

1. Lacking - protochordates (Urochordata & cepahlochordata)

2. Bearing - vertebrata

B. Split #2 - bearing or lacking jaws (Fig 34.8)

1. Lacking - agnathans (lampreys)

2. Bearing - all other

a. Jaws evolved from gill arch skeletal elements

C. Split #3 - bony or cartilaginous skeleton

1. Cartilagenous - chondrichthyes

2. Bony - all other

D. Split #4 - fins or limbs

1. Fins - Osteichthyes (bony fishes)

2. Limbs - tetrapods

a. Evolution - from lobe finned fishes, tetrapod condition may have evolved prior to lungs (Fig. 34.14)

E. Split #5 - bearing or lacking an amnion

1. Lacking - amphibians

a. eggs lack shells

b. Gas uptake and water remove is accomplished at the interface of the water and the egg

2. Amniotes - all other (Fig. 34.17)

a. Shelled eggs

b. Extra-embryonic membranes - form from embryo side of egg - eliminate wastes and carry out gas exchange

c. Amnion- one of the extra-embryonic membranes, surrounds the embryo in a fluid buffer, keeps it moist and acts as a shock absorber.

F. Split # 6 - scales & feathers vs. hair

1. Split within reptiles

2. Reptiles, birds, dinosaurs - scales &/or feathers

3. Mammals - hair

III. Vertebrate diversity (good summary in Table 34.1) - each trait only mentioned at the level at which it first appears, unless so noted, the trait exists in following groups

A. Agnathans - hagfishes and lampreys

1. Characterisitics

a. Lacking jaws

2. Groups

a. hagfishes

b. lampreys

B. Chondrichthyes

1. Characteristics

a. Jaws

b. Cartilagenous skeleton

c. Multiple gill slits

2. Groups

a. sharks - fusiform

b. skates and rays - dv compression, adapted to life on the bottom

C. Osteichthyes - primitive and advanced fishes

1. Characteristics

a. Bony skeleton

b. Fins

c. Operculum covers gill arches

2. Groups

a. Ray finned fishes - perched, trout, tuna, ect.

i. Very manuverable

ii. Oviparous

b. Lobe finned fishes

i. Lungfishes - bearing a lung, but lacking strong fins

ii. Coelacanth - lacking lung, bearing strong fins

D. Amphibia

1. Characteristics

a. Eggs are unshelled - tied to water

b. External fertilization - tied to water

c. Some entirely aquatic (bearing gills and limbs)

2. Groups

a. Salamanders - walking movement is undulatory, similar to fish swimming

b. Frogs and toads

i. Most effective terrestrial locomotion

ii. Metamorphosis of tadpole tied to water

iii. Tadpole very fish-like: gills, tail, no limbs

E. Reptilia

1. Characteristics

a. Amnionic, shelled eggs

b. Scales containing keratin

c. Internal fertilization

d. Ectotherms (vs. endotherms)

2. Groups

a. Turtles - protected by shell, very little change over time

b. Lizards and snakes

i. Lizards - most small, ectothermic, not as active or lg. as dinosaurs

ii. Snakes - evolved from burrowing lizards

c. Crocodiles and alligators

i. Large, predatory, confined to warm climates

F. Aves

1. Characteristics

a. Reptilian characteristics: anmionic eggs, scales on legs

b. Endothermic - warm blooded, metabolic rate important to flying

c. Feathers - adapted scales, perhaps originally as insulation. Light, honeycombed bones

d. Adaptation to make them lighter

i. Honeycombed bones

ii. Reduced organ systems (only one ovary)

iii. No teeth

2. Groups

a. Flightless - walking & swimming

b. Flying

i. diving & swimming

ii. carnivore, insectivore, herbivore, nectar feeders, etc

G. Mammals

1. Characteristics

a. Hair - not modified scales, mammals diverged from reptiles very early

b. Endothermic

c. Lactation

d. Tooth differentiation

2. Groups

a. Montremes - echidna, platapus

i. Egg layers

ii. Maintain other characteristics (lactation & hair)

b. Marsupials - oppossums, kangaroos, koalas, tasmanian wolf, etc.

i. Young born early in development

ii. Crawl to pouch to finish development during lactation

iii - convergent evolution of forms common (echidna and spiny anteater, wolves, etc.)

c. Placentals - all other

i. No egg, prolonged internal maturation

ii. Have a placenta, special organ that connects fetus to mother