Biology 104 CH 32: Animals—Chordates & Vertebrates

Chordate

Animal with a notochord, dorsal nerve cord, pharyngeal pouches, and postanal tail.

Phylum Chordata

Animal phylum containing vertebrates and invertebrate chordates like lancelets and tunicates.

Notochord

Flexible dorsal supporting rod in chordates, replaced by vertebral column in vertebrates.

Dorsal tubular nerve cord

Hollow nerve cord along the back; develops into brain and spinal cord.

Pharyngeal pouches

Paired embryonic structures developing into adult structures like gill slits or ear/throat parts.

Postanal tail

Tail extending beyond the anus, present during some stage of life.

Subphylum Vertebrata

Chordates with a vertebral column and skull; includes fish, amphibians, reptiles, birds, mammals.

Subphylum Tunicata

Marine invertebrate chordates; larvae have all chordate traits, adults are saclike filter feeders.

Subphylum Cephalochordata

Invertebrate chordates (lancelets) that retain all four chordate traits as adults.

Lancelet (class Leptocardii)

Knife-shaped cephalochordate retaining all chordate characteristics as an adult.

Tunicate (sea squirt)

Sessile marine filter feeder; adult mainly retains pharynx with gill slits.

Segmentation (in lancelets)

Repetition of body units seen as segmentally arranged muscles and nerve cord.

Vertebrate

Chordate in subphylum Vertebrata with vertebrae, a skull, and an endoskeleton.

Endoskeleton

Internal skeleton of bone or cartilage protecting organs and supporting the body.

Cephalization

Concentration of sensory organs and nervous tissue at the head end.

Amnion

Extraembryonic membrane surrounding the embryo in a fluid-filled protective sac.

Amniotic egg

Egg with specialized membranes protecting the embryo from drying out on land.

Evolutionary trend: jaws

Evolved first in cartilaginous fish from modified gill arches, allowing active predation.

Evolutionary trend: lungs and lobe-fins

Developed in early bony fish, leading toward amphibians and terrestrial vertebrates.

Evolutionary trend: jointed appendages

First appeared in amphibians, allowing effective locomotion on land.

Evolutionary trend: reproduction on land

Evolved amniotic eggs or membranes, eliminating the larval water stage.

Jawless fishes (agnathans)

Fish with cylindrical bodies, smooth scaleless skin, and no jaws or paired fins.

Class Myxini (hagfish)

Jawless scavenger fish that has a skull but lacks vertebrae.

Class Cephalaspidomorphi (lampreys)

Jawless parasitic fish with a true vertebral column and sucker-like mouth.

Cartilaginous fishes

Fishes with a skeleton made of cartilage, including sharks, skates, and rays.

Class Chondrichthyes

Vertebrate class of cartilaginous fishes such as sharks, skates, and rays.

Gill slits (cartilaginous fishes)

Five to seven open gill slits on each side, lacking a protective cover.

Spiracles

Openings behind the eyes of many sharks/rays leading to gill chambers.

Dermal denticles

Small teeth-like scales covering shark skin, giving a sandpaper feel.

Lateral line system

Pressure-sensitive cells along fish sides detecting water movements and vibrations.

Electroreception (sharks and rays)

Ability to sense electric currents produced by muscle contractions of other animals.

Bony fishes

Fishes with bony skeletons; includes ray-finned and lobe-finned fishes.

Ray-finned fishes

Bony fishes with fins supported by thin bony rays and a swim bladder.

Swim bladder

Gas-filled sac in many bony fishes used to control buoyancy.

Single-circuit circulation (fish)

Circulatory pathway where blood flows heart to gills to body in one loop.

Two-chambered heart

Fish heart with one atrium and one ventricle.

Lobe-finned fishes

Bony fishes with fleshy, lobed fins containing bones homologous to tetrapod limbs.

Coelacanth

Lobe-finned fish once thought extinct; considered a living fossil.

Class Amphibia

Vertebrate class including salamanders, frogs, toads, newts, and caecilians.

Amphibian

Vertebrate typically having aquatic larvae and mainly terrestrial adults.

Caecilian

Fossorial, wormlike, limbless amphibian that spends most of its life underground.

Cutaneous respiration

Gas exchange that occurs across moist skin, common in amphibians.

Three-chambered heart (amphibians)

Heart with two atria and one ventricle, found in amphibians.

Class Reptilia

Vertebrate class including turtles, lizards, snakes, crocodilians, and birds.

Keratinized scales

Tough, keratin-rich scales covering reptile bodies to reduce water loss.

Negative pressure breathing (reptiles)

Breathing mechanism where expanding the rib cage draws air into lungs.

Ectothermic

Using environmental heat sources; body temperature changes with surroundings.

Class Aves

Birds; feathered reptiles with wings, hollow bones, and endothermy.

Feathers

Modified scales covering birds, used for flight and insulation.

Keel (on sternum)

Prominent ridge on the bird's sternum providing attachment for flight muscles.

Air sacs (birds)

Lung extensions increasing gas exchange efficiency and lightening the body.

Four-chambered heart (birds)

Heart that fully separates oxygen-rich and oxygen-poor blood.

Endothermic

Maintaining a relatively constant body temperature using metabolic heat.

Uric acid

Semi-solid nitrogenous waste excreted by birds and reptiles to conserve water.

Birds of prey

Birds with notched beaks and sharp talons adapted for hunting.

Shorebirds

Birds with long probing beaks and stiltlike legs for shallow water feeding.

Woodpeckers

Birds with sharp chisel-like beaks adapted for drilling into wood.

Waterfowl

Birds with broad beaks and webbed toes adapted for swimming.

Penguins

Flightless birds whose wings are modified as paddles for swimming.

Songbirds

Birds with perching feet; many produce complex songs.

Class Mammalia

Vertebrate class characterized by hair, mammary glands, and endothermy.

Mammal

Endothermic vertebrate with hair and milk-producing mammary glands.

Mammary gland

Gland that produces milk to nourish the young in mammals.

Monotremes

Egg-laying mammals with a cloaca; found only in Australia and New Guinea.

Cloaca

Common chamber for feces, excretory wastes, and sex cells in monotremes.

Marsupials

Mammals whose young are born immature and complete development in a pouch.

Placental mammals (eutherians)

Mammals using a placenta for internal development in the uterus.

Placenta

Organ exchanging materials between fetal and maternal blood.

Differentiated teeth

Varied tooth types (incisors, canines, premolars, molars) adapted to different functions.

Incisors

Front teeth with cutting edges for nipping or slicing.

Canines

Pointed teeth often used for capturing and killing prey.

Premolars and molars

Back teeth with broad surfaces used for grinding and chewing food.

Herbivore

Animal that primarily eats vegetation.

Carnivore

Animal that primarily eats meat.

Omnivore

Animal that eats both plant and animal food.

Order Rodentia

Mammalian order whose members have ever-growing incisors.

Order Carnivora

Mammalian order with long canine teeth adapted for eating meat.

Order Chiroptera

Mammalian order of bats; wings are supported by elongated digits.

Order Perissodactyla

Mammalian order including horses; odd-toed hoofed legs adapted for speed.

Order Cetacea

Mammalian order including whales; forelimbs modified as paddles.

Order Primates

Mammalian order adapted to arboreal life with mobile limbs and opposable digits.

Opposable thumb

Thumb that can touch other fingers, allowing precise gripping.

Arboreal life

Life spent primarily in trees.

Suborder Strepsirhini

Primates including lemurs, aye-ayes, bush babies, and lorises.

Suborder Haplorhini

Primates including monkeys, apes, and humans.

Anthropoids

Group including hominids, gibbons, Old World monkeys, and New World monkeys.

Old World monkeys

Monkeys from Africa/Asia lacking prehensile tails; protruding noses.

New World monkeys

Monkeys from South/Central America with flat noses; often prehensile tails.

Hominids

Group including humans, chimpanzees, gorillas, and orangutans.

Hominins

Humans and extinct human-like relatives characterized by bipedalism.

Bipedalism

Ability to walk upright on two feet.

Mosaic evolution

Pattern where different traits evolved at different times rather than all together.

Sahelanthropus tchadensis

Early fossil (~7 MYA) with small canines but an apelike braincase.

Orrorin tugenensis

Fossil (~6 MYA) showing adaptations for bipedalism and climbing.

Ardipithecus kadabba

Early ardipithecine (~5.6 MYA) known mainly from teeth and bone fragments.

Ardipithecus ramidus (Ardi)

Hominin (~4.4 MYA) that walked erect but had an opposable big toe.

Australopithecines

Group of early hominins; includes gracile Australithecus and robust Paranthropus.

Australopithecus africanus

Australopithecine (~2.9 MYA) with upright posture and apelike limb proportions.

Australopithecus afarensis (Lucy)

Bipedal hominin (~3.18 MYA) with an apelike brain size.

Paranthropus

Robust australopithecine genus with heavier skull and jaws.