Chapter 34: Deuterostomes

Echinodermata

Marine deuterostomes with endoskeleton and pentaradial symmetry, including sea stars, urchins, and sea cucumbers.

Pentaradial symmetry

Adult body plan of echinoderms with parts arranged in fives around a central axis.

Bilateral larvae

Echinoderm larvae are bilaterally symmetrical, showing evolutionary link to bilaterians.

Endoskeleton (Echinoderms)

Internal calcium carbonate plates (ossicles) covered by epidermis providing support.

Ossicles

Calcium carbonate plates forming echinoderm endoskeleton.

Nerve ring

Echinoderm nervous system organized around central ring with radiating branches, lacking brain.

Regeneration

Ability of many echinoderms to regrow lost arms or body parts.

Asexual reproduction (Echinoderms)

Some species reproduce by splitting

Gonochoric

Having separate male and female individuals, as in most echinoderms.

Asteroidea

Class of echinoderms including sea stars and sea daisies, typically with five arms.

Crinoidea

Sea lilies and feather stars, sessile or free-swimming echinoderms with feather-like arms.

Holothuroidea

Sea cucumbers, soft-bodied echinoderms that lack arms and can eviscerate organs defensively.

Echinoidea

Sea urchins and sand dollars, echinoderms with movable spines and no arms.

Ophiuroidea

Brittle stars, largest echinoderm class with easily detachable slender arms.

Chordata

Phylum including animals with a notochord, nerve cord, pharyngeal slits, and postanal tail.

Notochord

Flexible rod that supports the body in chordate embryos, replaced by vertebral column in vertebrates.

Dorsal nerve cord

Hollow cord of nervous tissue running along the back of chordates.

Pharyngeal slits

Openings in the pharynx that may develop into gills or other structures.

Postanal tail

Tail extending beyond anus, providing movement in many chordates.

Urochordata

Subphylum of chordates including tunicates and sea squirts.

Tunicate

Marine filter-feeding animal with cellulose-like tunic covering body.

Tunic

Protective cellulose sac secreted by adult tunicates.

Cephalochordata

Lancelets, small fishlike chordates retaining notochord and dorsal nerve cord throughout life.

Lancelet

Scaleless marine chordate burrowing in sediment, feeding on plankton.

Vertebrata

Chordates with vertebral column and distinct head containing sensory organs.

Vertebral column

Series of bones or cartilage segments enclosing and protecting the dorsal nerve cord.

Endoskeleton (Vertebrates)

Internal skeleton of bone or cartilage allowing large body size and movement.

Closed circulatory system

Vertebrate system where blood is contained within vessels.

Vertebrate organs

Include liver, kidneys, endocrine glands, and heart.

Fishes

First vertebrates, aquatic animals with gills, jaws, and paired fins.

Agnathans

Jawless fishes such as hagfish and lampreys.

Jaws

Evolved from gill arches, allowing active predation.

Chondrichthyes

Cartilaginous fishes including sharks, skates, and rays.

Shark skeleton

Cartilage strengthened with calcium carbonate.

Teeth (Sharks)

Derived from skin scales, replaced continuously.

Lateral line system

Sensory structure in fish detecting pressure and vibrations in water.

Internal fertilization (Sharks)

Sperm deposited inside female body

Bony fish

Fishes with bony skeleton, swim bladder, and operculum.

Swim bladder

Gas-filled sac regulating buoyancy in bony fish.

Operculum

Protective bony plate covering gills, enabling water pumping.

Ray-finned fish

Bony fish with fins supported by bony spines and lacking muscles in fins.

Lobe-finned fish

Fish with fleshy, muscular fins supported by bones, precursor to tetrapods.

Lungfish

Air-breathing lobe-finned fish that can survive in low-oxygen water.

Coelacanth

Ancient lobe-finned fish once thought extinct, rediscovered in 1938.

Amphibia

First vertebrates to live on land, descendants of lobe-finned fish.

Legs (Amphibians)

Adaptation to support body weight on land.

Cutaneous respiration

Gas exchange through moist skin supplementing lungs in amphibians.

Pulmonary veins

Carry oxygenated blood from lungs to heart.

Partially divided heart

Improves oxygen separation between systemic and pulmonary circuits.

Ichthyostega

Early amphibian with limbs and ribs supporting lungs and heart.

Tiktaalik

Transitional fossil between fish and amphibians with limb-like fins.

Anura

Order including frogs and toads, tailless amphibians.

Frog

Moist-skinned amphibian with long legs, aquatic larvae, and external fertilization.

Toad

Dry-skinned amphibian with short legs adapted for land.

Caudata

Order of salamanders with tails and moist skin.

Apoda

Order of caecilians, legless burrowing amphibians.

Reptilia

Vertebrates with amniotic eggs, dry scaly skin, and thoracic breathing.

Amniotic egg

Egg with extra membranes that prevent desiccation on land.

Chorion

Outermost membrane allowing gas exchange in amniotic egg.

Amnion

Fluid-filled sac protecting embryo from shock.

Yolk sac

Stores food for developing embryo.

Allantois

Stores nitrogenous waste and aids gas exchange in egg.

Ectothermic

Body temperature depends on external environment, characteristic of reptiles.

Chelonia

Order including turtles and tortoises.

Carapace

Dorsal shell of turtles.

Plastron

Ventral shell of turtles.

Rhynchocephalia

Order including tuatara, a lizardlike reptile from New Zealand.

Parietal eye

Light-sensitive structure on top of tuatara’s head.

Squamata

Order of lizards and snakes, most diverse reptile group.

Lepidosauria

Clade including squamates and tuataras.

Crocodylia

Order including crocodiles, alligators, and gharials.

Archosauria

Clade including crocodiles, birds, and extinct dinosaurs.

Birds

Feathered, endothermic reptiles adapted for flight.

Feathers

Modified keratin scales used for flight and insulation.

Flight skeleton

Light, hollow bones fused for strength during flight.

Archaeopteryx

Earliest known bird showing both reptilian and avian traits.

Theropod dinosaurs

Carnivorous dinosaurs that gave rise to birds.

Endothermy (Birds)

High body temperature maintained internally for sustained activity.

Air sacs (Birds)

Provide continuous airflow through lungs for efficient respiration.

Four-chambered heart

Separates oxygenated and deoxygenated blood in birds and mammals.

Beak adaptation

Shape indicates diet and feeding habits in birds.

Mammalia

Endothermic vertebrates with hair and mammary glands.

Hair

Keratin filament providing insulation, camouflage, and sensory function.

Mammary glands

Produce milk to nourish young.

Diaphragm

Muscle aiding in respiration by ventilating lungs.

Placenta

Organ connecting fetus and mother for nutrient and gas exchange.

Specialized teeth

Different types adapted for herbivory, carnivory, or omnivory.

Ruminant

Herbivorous mammal with chambered stomach for cellulose digestion.

Horns

Permanent keratin-covered bone structures.

Antlers

Bone structures shed annually, found in deer.

Bats

Only mammals capable of true flight using skin membrane wings.

Echolocation

Navigation using sound reflection in bats and dolphins.

Monotremes

Egg-laying mammals such as platypus and echidnas.

Cloaca

Single opening for excretion and reproduction in monotremes.

Marsupials

Mammals with short gestation and pouch development, e.g., kangaroo.

Placental mammals

Mammals with long gestation, young develop via placenta.

Primates

Mammalian order including lemurs, monkeys, apes, and humans.

Binocular vision

Overlapping visual fields for depth perception in primates.

Opposable thumb

Allows grasping and tool use in primates.