BIOL 2251 Exam 3

Deuterostomia

a group of higher phyla in which cleavage is indeterminate and ancestrally radial; anus forms from blastopore

Echinodermata

radially symmetrical marine invertebrates including e.g. starfish and sea urchins and sea cucumbers

Asteroidea

sea stars; about 1500 living species; pentaradial symmetry

ophiuroidea

brittle stars and basket stars; largest group of echinoderms; over 2000 extant species; found in benthic marine habitats

sessile

attached at the base, fixed to one spot

water vascular system

a set of canals and specialized tube feet that work with dermal ossicles to form a hydraulic system; primary functions are locomotion, food gathering, respiration and excretion

tube feet

Numerous small, muscular, fluid-filled tubes projecting from an echinoderm; part of water-vascular system; used in locomotion, clinging, food handling, and respiration

pentaradial symmetry

a variation of radial symmetry that arranges roughly equal parts around a central axis at orientations of 72 degrees apart

pedicellaria

One of many minute, pincerlike organs on the surface of certain echinoderms

dermal gills

In echinoderms, gas exchange and excretion occur by diffusion through the thin walls of the dermal gills and tube feet.

madreporite

Sievelike structure that is the intake of the water-vascular system of Echinoderms

stone canal

A tube that contains calcareous deposits and leads from the madreporite to the ring of the water vascular system surrounding the mouth

ring canal

the circular water tube that surrounds the esophagus of echinoderms

radial canal

Canals along the ambulacra radiating from the ring canal of echinoderms

ampulla

muscular vesicle above the tube foot in water vascular system

podium

a foot-like structure

ambulacral groove

one of the radial areas bearing the tube feet

regeneration

The ability to regrow a missing part of the body

cardiac stomach

a sack like stomach located at the center of the body that may be pushed out of the body to engulf and digest food

pyloric stomach

the second stomach in echinoderms that receives partially digested food from the cardiac stomach

Hemichordata

have a stomochord that is not homologous to the notochord found in chordates

notochord

elongated cartilaginous cellular cord, enclosed in a sheath, that forms the primitive axial skeleton of chordate embryos, adult cephalochordates, and jawless vertebrates

acorn worm

sluggish, wormlike animals that live in burrows or under stones; aka Enteropneusts

proboscis

the long snout of an animal; a nose, especially a prominent one; a tubular organ

collar

derived from the mesosoma

What are the two most diverse classes within Echinodermata?

Asteroidea (1500) and Ophiuroidea (2000)

Is pentaradial symmetry considered an ancestral or derived character?

It is a derived characteristic because it was not present in a common ancestor

What is the function of the pedicellaria?

keep the body free of debris, protect the papulae, and sometimes aid in food capture

How do Echinoderms obtain oxygen?

They obtain oxygen from gas exchange through the papulae that cover their skin

What are the functions of the water vascular system?

Locomotion, food gathering, respiration and excretion

What is the name of the calcareous plates that form the endoskeleton of Echinoderms?

Ossicles

Describe the path of water within a sea star.

madreporite; stone canal; ring canal; radial canal; tube feet

Is the notochord of hemichordates homologous with chordates?

It is not because the notochord is really just an evagination, or protrusion, of their mouth cavity

Are hemichordates more closely related to chordates or echinoderms?

They are more closely related to echinoderms based on analysis of 18S rDNA and Hox genes

pharyngeal slits

Slits used for filter feeding in primitive chordates and have been adapted for other functions in more highly evolved chordates; a common feature of all chordates

postanal tail

provides motility for larval tunicates and amphioxus to swim, evolved for propulsion in water; efficiency increased in fish with the addition of fins

dorsal hollow nerve cord

a hollow, tubular structure derived from ectoderm, which is located dorsal to the notochord in chordates

endostyle

ciliated grooves in the floor of the pharynx of tunicates, cephlochordates, and larval lampreys; used for accumulating and moving food particles to the stomach

cartilage

translucent elastic tissue that forms most of the skeleton of embryos, very young vertebrates, and adult cartilaginous fishes, such as sharks and rays

Cephalochordata

also knows as lancelets or amphioxus, approx. 29 species, has the 5 distinctive characteristics of chordates in simple form, sexes are separate, Adults retain all the chordate key characteristics.

perfect chordates

lancelets; cephlochordates

lancelets

Subphylum Cephalochordata

Urochordata

include 1600 species, most are sessile, have a "tunic" that surrounds the animal and contains cellulose

tunicates

Members of the subphylum Urochordata, sessile marine chordates that lack a backbone

incurrent siphon

a tube through which water enters the body of a tunicate

excurrent siphon

tube that expels water from the body of a tunicate

Vertebrata

possess vertebra along the notochord, allows for larger overall body size, large and very diverse subphylum

jawless fishes

aka agnathans

aspidin

primitive bone like tissue, comprised of dentine and enameloid

Ostracoderms

earliest agnathans, very abundant in their time period, armored jawless filter feeders, had tails and many did not have fins only a few inches long

Heterostracans

A group of extinct fishes with dermal armor and no jaws or paired fins; known from the Ordovician to Devonian periods

Osteostracans

developed paired fins that stabilized movement, jawless and toothless, head was armored with head shield

Conodonts

among the earliest vertebrates in the fossil record, had mineralized dental elements in mouth and pharynx, known as gnathostomes

jawed fishes

gnathostomes

placoderms

A group of heavily armored jawed fishes of the Devonian and Carboniferous periods

Dunkleosteus

placoderm, armored, became extinct in Devonian period, no decendants

Acanthodians

diversified into bony fishes, had large eyes and fins with spines

What are the derived characters of chordates?

notochord, dorsal hollow nerve cord, pharyngeal slits, postanal tail, endostyle

Describe the function of each of the characters listed above

notochord - permits wave-like movement of the body

dorsal hollow nerve cord - forms spinal cord and brain in vertebrates

pharyngeal slits - used for filter feeding

postanal tail - propulsion through water

endostyle - secretes mucus to trap food particles

What is the composition of the notochord? Why is it considered a hydrostatic structure?

composed of fluid filled cells enclosed in a fibrous sheath extending the length of the body; it is hydrostatic because it is a flexible rod of fluid filled cells

List the subphyla within Phylum Chordata

Urochordata (Tunichordata), Cephlochrodata, Vertebrata (Craniata)

Why are cephalochordates considered the "perfect chordates"?

They possess all five of the definitive characteristics of Chordates

Why are tunicates considered chordates?

The larval forms posses all five chordate characteristics

Differentiate between heterostracans and osteostracans.

Osteostracans had pectoral fins that increased mobility compared to heterostracans

Differentiate between ostracoderms and placoderms. What important evolutionary adaptations
first appeared in each group?

Ostracoderms - first vertebrates; jawless

Placoderms - first jawed vertebrates

What is the most accepted explanation for the evolution of jaws? What group of fish was the
first to have jaws?

Placoderms were the first to have jaws

Jaws arose through modification of gill arches due to increased metabolic demands of early vertebrates

The earliest known mineralized internal structure in vertebrates are associated with which
function?

feeding

What is the composition of notochord, cartilage and bone?

Notochord- made of glycoproteins and case of collagen

Cartilage- made mostly by collagen fibers

Bone- mostly comprised by minerals such as calcium and phosphorus

gills

organs found in aquatic animals that take in water to extract the oxygen; similar to spiracles in terrestrial arthropods

Caudal fin

used for propulsion, forward movement

Operculum

Draws water over gills and protects the gills

pelvic fin

helps fish move up and down, turn sharply and stop quickly

Dorsal fin

prevents fish from rolling, provides balance

Lateral line system

Formed by neuromasts and detects water currents and vibrations

agnathans

The most primitive of the early fishes were the

hagfishes

Myxini, jawless, Cyclostomata, skull no vertebral column

slime glands

specialized subcutaneous organs that produce a high-volume, protective slime used for defense, feeding, and locomotion

lampreys

Petromyzontida, Cyclostomata, Some features shared gnathostomes, cartilaginous skeleton

Devonian

The "Age of Fishes"

cyclostomata

The most primitive of the early fishes were the

Chondrichthyes

Cartilaginous Fishes, 1200 living species, Well-developed sense organs, powerful jaws, and most are predaceous, True bone is completely absent throughout the class

cartilage

translucent elastic tissue that forms most of the skeleton of embryos, very young vertebrates, and adult cartilaginous fishes, such as sharks and rays

ampullae of Lorenzini

electroreceptors, sensory organs able to detect electric fields, found mostly in Chondrichthyes

Osteichthyes

Bony fishes, Contains 96% of living fishes and all living tetrapods, Lung or swim bladder is present

Endochondral bone

replaces cartilage during development

gas bladder

an internal, gas-filled organ in bony fish that regulates buoyancy

ray-finned fishes

The most diverse fish group, Actinopterygii, Includes teleosts, Most species-rich clade of living vertebrates

Cladistia (bichirs)

Rhombic ganoid scales; lungs; spiracle present; dorsal fin consisting of 5-18 finlets (16 species)

Chondrosteans (Sturgerons and paddlefishes)

skeleton primarily cartilage; caudal fin heterocercal; large scutes or tiny ganoid scales present (29 species)

Neopterygians (gar and bowfin)

skeleton primarily bone; caudal fin usually homocercal; scales cycloid, ctenoid, or rarely ganoid (27,000 species)

Teleosts

modern bony fishes; class Neopterygii

Mudskippers

Periopthalmus; make extensive land excursions to graze on algae and capture insects

Cutaneous air breathing

form of respiration in which gas exchange occurs across the skin or outer integument of an organism rather than gills or lungs

Facultative air breather

an organism that can use oxygen but also has anaerobic methods of energy production

Obligate Air-breather

a term used in fish physiology to describe those that respire entirely from the atmosphere

Sarcopterygii

lobe-finned fishes, tetrapods; skeleton ossified, gills covered by operculum, paired fins and internal skeleton, diphycercal tail

Lobe-Finned Fish

fish that are lobe liked, fleshy fins, probably anscestors of first land vertebrate; Sarcopterygii

Lungfishes

A bony fish that generally inhabits stagnant waters and gulps air into lungs connected to a pharynx; Dipnoi

Coelacanths

ancient group of fish related to the lobe-finned fish ancestors of the amphibians; Actinistia; live deep in oceans, were thought to be extinct

Tetrapods

vertebrate animals having four feet, legs or leglike appendages