(These are Most Repeated Questions) 1. Reproduction and development of cephalopods (Cephalochordates) (Short & LONG) Reproduction: ? Cephalochordates are dioecious. ? Gonads bulge into the atrium from the lateral body wall. ? Gametes are shed into the atrium and leave the body through the atriopore. Development: ? External fertilization leads to a bilaterally symmetrical larva. ? Larvae are free-swimming ? But they eventually settle to the substrate before metamorphosing into adults 2. Lateral line system (3) ? Fishes has a lateral-line system. ? The lateral-line system consists of sensory pits in the epidermis In these pits are receptors that are stimulated by water ? Lateral lines are used to detect either water currents, or a predator ? Fishes may also detect low-frequency sounds with these receptors 3. Feeding In Enteropneusta (Acorn worms) ? Cilia and mucus assist acorn worms in feeding. ? Detritus and other particles adhere to the mucus-covered proboscis. Tracts of cilia transport food and mucus posteriorly and ventrally. ? Cilia and mucus assist acorn worms in feeding. ? Detritus and other particles adhere to the mucus-covered proboscis. Tracts of cilia transport food and mucus posteriorly and ventrally. 4. Four Unique characteristics of chordates (Chordata) Four unique characteristics present at some stage in development: ? Notochord ? Pharyngeal slits or pouches ? Dorsal tubular nerve cord ? Post anal tail Presence of an endostyle or thyroid gland (Also Remember other Characteristics, If Examiner Asked, you should be Able to write it) ? Bilaterally symmetrical ? Deuterostome animals ? Complete digestive tract. ? Ventral, contractile blood vessel (heart) ? The phylum is named after the notochord ? It consists of a connective-tissue sheath that encloses cells 5. Class Myxini (Hagfishes): (Both in short & Long) ? Hagfishes are members of the class Myxini (miks??-ne) (Gr. myxa, slime). ? Hagfishes live buried in the sand and mud of marine environments. ? They feed on soft-bodied invertebrates and scavenge dead and dying fish. ? When hagfishes find a suitable fish, they enter the fish through the mouth and eat the contents of the body, leaving only a sack of skin and bones. ? Anglers must contend with hagfishes because they will bite at a baited hook. ? Most zoologists now consider the hagfishes to be the most primitive group of vertebrates. 6. Class Tunicates (Ascidians) Tunicates derive their name from a thick extracellular body covering, called a tunic that is made up of cellulose-like, complex sugars. Another interesting feature of tunicates is their circulatory system. Instead of blood vessels, the heart pumps blood through a number of small pockets called sinuses. In addition, the heart periodically changes the direction that it pumps blood 7. Cartilaginous fishes ? Endoskeleton of cartilage ? Paired fins, movable jaws, gill slits ? Rough sandpaper ? like skin o Placoid scales ? Pointed tip that is directed backward ? Same composition as teeth ? Example: Sharks, rays, skates, and ratfishes. 8. Explain reproduction in Enteropneusta (Acorn worms) ? Because acorn worms are small, respiratory gases and metabolic waste products (principally ammonia) probably are exchanged by diffusion across the body wall. ? In addition, respiratory gases are exchanged at the pharyngeal slits. ? Cilia associated with pharyngeal slits circulate water into the mouth and out of the body through the pharyngeal slits. ? As water passes through the pharyngeal slits, gases are exchanged by diffusion between water and blood sinuses surrounding the pharynx. 9. Write characters of Super Class Osteichthyes: Bony Fish ? Largest group of living vertebrates ? Gills covered by operculum ? Usually swim bladder ? Highly maneuverable fins ? Cycloid scales 10. Define Amplexus ? The male grasps the female in a position called amplexus ? The male releases sperm as the female releases eggs. ? Little is known of caecilian breeding behavior. 11. What is ram ventilation? ? Fishes have Muscular pumping mechanism. ? Muscles surrounding the pharynx and the opercular cavity, power this pump. ? Maintain water flow by holding their mouths open ? This method is called ram ventilation 12. What is cirri? An oral hood projects from the anterior end of cephalochordates. Ciliated, fingerlike projections, called cirri, hang from the ventral aspect of the oral hood and are used in feeding. 13. Chimaera ? A frequently studied example, Chimaera, has a large head with a small mouth surrounded by large lips. A narrow, tapering tail has resulted in the common name ?ratfish.? 14. General characteristic of Enteropneusta (Acorn worms) (Remember all Characteristics for Long Question) ? Marine worms ? Usually range in size between 10 and 40 cm ? More than 70 species ? Most occupy U-shaped burrows in sandy and muddy substrates between the limits of high and low tides. ? Proboscisis a short, conical projection at the worm?s anterior end. A ring like collar is posterior to the proboscis ? An elongate trunk is the third division of the body A ciliated epidermis and gland cells cover acorn worms. ? The mouth is located ventrally between the proboscis and the collar. ? A variable number of pharyngeal slits, from a few to several hundred, are positioned laterally on the trunk. ? Pharyngeal slits are openings between the anterior region of the digestive tract, called the pharynx, and the outside of the body. 15. Partition of atrium in Urodeles and Anuran Atrium is partially divided in urodeles and completely divided in anurans. Long Questions: (These are Most Repeated Questions) 1. Why are Protochordates not classified as true Chordata? ? A hollow dorsal nerve cord ? Gill slits, ? A stiff supporting rod, ? The notochord, ? The forerunner of the backbone. ? The protochordates differ chiefly from the vertebrates in not having a backbone. 2. Characteristics of Protochordata (Protochordates) ? They are generally found in marine water. ? Their body is bilaterally symmetrical, triploblastic, and coelomated. ? At a certain stage of their lives, their body develops a long, rod-like structure for support called notochord. ? They exhibit organ system level of organization. ? Eg., Herdmania, Amphioxus 3. Explain class Myxini (Hagfishes) ? Hagfishes are members of the class Myxini (miks??-ne) (Gr. myxa, slime). ? Hagfishes live buried in the sand and mud of marine environments. ? They feed on soft-bodied invertebrates and scavenge dead and dying fish. ? When hagfishes find a suitable fish, they enter the fish through the mouth and eat the contents of the body, leaving only a sack of skin and bones. ? Anglers must contend with hagfishes because they will bite at a baited hook. ? Most zoologists now consider the hagfishes to be the most primitive group of vertebrates. 4. Gas Exchange in Fishes Less than 2.5% of the oxygen present in air. Fishes pass water across gill surfaces and extract the small amount of oxygen present in the water. They have Muscular pumping mechanism. Muscles surrounding the pharynx and the opercular cavity, power this pump. Maintain water flow by holding their mouths open. This method is called ram ventilation Gas exchange across gill surfaces is very efficient. Gill (visceral) arches support gills. Gill filaments extend from each gill arch called pharyngeal lamellae. Branchial arteries carry blood to the gills and into gill filaments. The arteries break into capillary beds in pharyngeal lamellae. Gas exchange occurs as blood and water move in opposite directions. This countercurrent exchange mechanism provides very efficient gas exchange 5. Respiration in Enteropmeusta Because acorn worms are small, respiratory gases and metabolic waste products (principally ammonia) probably are exchanged by diffusion across the body wall. In addition, respiratory gases are exchanged at the pharyngeal slits. Cilia associated with pharyngeal slits circulate water into the mouth and out of the body through the pharyngeal slits. As water passes through the pharyngeal slits, gases are exchanged by diffusion between water and blood sinuses surrounding the pharynx 6. Characteristics of Anurans ? The diets of some anurans, however, are more diverse. ? For example, a bullfrog prey on small mammals, birds, and other anurans. ? Anurans and plethodontid salamanders use their tongue and jaws in a flip-and-grab feeding mechanism ? Atrium is partially divided in urodeles and completely divided in anurans. ? The lungs of anurans are subdivided ? Critical temperature extremes for some anurans between 3 and 41? C ? The eyes of some anurans are on the front of the head, providing the binocular vision ? The ears of anurans consist of a tympanic membrane, a middle ear, and an inner ear. ? Anurans use low- and high-frequency sounds in different situations. ? A few anurans have terrestrial nests that are kept moist by being enveloped in foam ? Male vocalizations and tactile cues are important for anurans. ? Sound production is primarily a reproductive function of male anurans, advertisement calls, and announce to other males ? Paternal care may occur in species with external fertilization (predominantly anurans). 7. Order Anura (Salientia) ? Tail absent in adult ? Eyelids and tympanum present ? Skin scaleless and loose ? Further divided into five suborders ? Amphicoela, Opisthocoela, Procoela, Diplasiocela ? E.g. Frog and Toad American toad (Bufo americanus) ? Shortened vertebral column (nine or fewer presacral vertebrae) ? Presence of a urostyle formed from developing tail vertebrae. ? Absence of tail in adults. ? Hind limb longer than forelimb. ? Fusion of radius and ulna into a single element. ? Fusion of tibia and fibula into a single element. 8. Characteristics of Chordates ? Notochord ? Pharyngeal slits or pouches ? Dorsal tubular nerve cord ? Post anal tail Presence of an endostyle or thyroid gland ? Bilaterally symmetrical ? Deuterostome animals ? Complete digestive tract. ? Ventral, contractile blood vessel (heart) ? The phylum is named after the notochord ? It consists of a connective-tissue sheath that encloses cells 9. Paddle fishes: Paddlefishes are large, freshwater chondrosteans. They have a large, paddle like rostrum that is innervated with sensory organs believed to detect weak electrical fields. They swim through the water with their large mouths open, filtering crustaceans and small fishes. Paddlefishes are filter feeders. They are found mainly in lakes and large rivers of the Mississippi River basin and are also known from western North America and China 10. Explain Osmoregulation in marine and freshwater fishes. Osmoregulation in Marine Fish Marine water is hypertonic to fish blood. If the fish were to lose water and gain salt, it would dry out. To compensate, they drink water but this brings in salt. They absorb a controlled amount of water through the mouth and the gill membranes. Due to this intake of water, they produce large quantities of urine through which a lot of salt is lost. The salt is replaced with the help of mitochondria-rich cells in the gills. Osmoregulation in Fresh water Fish Freshwater fishes are hypertonic to their surrounding environment, which means that the concentration of salt is higher in their blood than their surrounding water. They absorb a controlled amount of water through the mouth and the gill membranes. In freshwater fishes, water will diffuse into the body of the fish, so it excretes a very hypotonic or dilute urine to expel all the excess water. Gills absorb salt to compensate for salt lost in urine. This is how they maintain water balance. 11. Characteristics of Cephalochordates ? Members of the subphylum Cephalochordata are called lancelets. ? They are distributed throughout the world?s oceans in shallow waters that have clean sand substrates. ? Cephalochordates are small (up to 5 cm long), tadpole like animals. ? They are elongate, laterally flattened, and nearly transparent. ? They spend most of their time in a filter feeding position partly to mostly buried with their anterior end sticking out of the sand ? The notochord of cephalochordates extends from the tail to the head, giving them their name. ? Unlike the notochord of other chordates, most of the cells are muscle cells, making the notochord somewhat contractile. ? Both of these characteristics are probably adaptations to burrowing. ? Median dorsal fin and a caudal fin also aid in swimming. ? An oral hood projects from the anterior end of cephalochordates. ? Ciliated, fingerlike projections, called cirri, hang from the ventral aspect of the oral hood and are used in feeding. ? The posterior wall of the oral hood bears the mouth opening that leads to a large pharynx