Vertebrates

Chapter 34

Chordata Characteristics

Invertebrate chordates• Cephalachordata

– Lancelets

• Urochordata– Tunicates, sea slugs

• Vertebrates may have evolved from a sexually mature larval urochordate

• Metamorphosis is eliminated• Leads to vertebrate lifecycle

Subphylum: Vertebrata• Cephalization• Vertebrate skeleton• Brain protected by skull• Closed circulatory system• Gills or lungs• Kidneys for excretion• dioecious• How do these characteristics enhance

success of vertebrates?

Fishes

• Very successful vertebrates– Fast streamlined body plan– Excellent sensory organs– Highly developed organs for osmoregulation– Complex behavior– 2 chambered heart

Classes of Fish

• Petromyzontida– Lamprey– Jawless

• Chondrichthyes– Sharks, rays– Cartilage skeletons

• Osteichthyes– Bony fish– Scales and fins– Most efficient swimmers, very numerous

What possible events led to movement onto land?

Fossilized and modern coelocanths

Life on Land

Problems:• No support on land• Gills stick together• Ammmonia no

longer a good source of excretory waste

• Dehydration• Sound light smell is

perviecved differently on land

Solutions• cartilage bone• Lungs• Excrete concentrated

urea uric acid

• Skin and scales• Adapt ability to perceive

sound, smell and light differently

Amphibia• Shoulder hip and girdles act to

strengthen limbs for life on land• Heart with 3 chambers• Bladder• In what ways are amphibians similar to

brypohytes?• They are not completely free from water

– Reproduction– Dessication (skin must stay moist)

                                                                

Reptilia• Completely free from water

• Amniote egg

• Scaly skin

• 3-4 chambered heart

• Uric acid as nitrogenous waste

• In what way are these animals still limited?

• Ectothermic

                                      

                           

                  

Aves• Evolved from reptiles• Flying dinosaurs• Bones and feathers are adapted for

flight• 4 chambered heart• Endothermic• Efficient 1 way lungs• Excrete uric acid

Mammalia• Hair• Mammary glands• Placenta connects fetus to mom

(missing in marsupials)• Diaphragm for ventilation of lungs• 4 chambered heart• Endothermic• Large brains• Diverged from reptilian ancestors earlier

than the birds

Major groups• Monotremes:

– Platypuses, lay eggs– Mixture of reptilian and mammalian traits

• Marsupials– Non-placental– Young born early and develop within pouch– Convergent evolution with placental mammals

• Placental Mammals– Bats, shrews– Herbivores, rabbits, cows, whales, elephants– Carnivores: seals and relatives– Primates and rodents