Chapter 30 Chordates

30-1 Phylum Chordata Chordate Characteristics: Notochord. All chordate embryos have a notochord, which is a longitudinal, flexible rod of cartilage located between the gut and the dorsal nerve cord. The notochord may persist into adulthood in some chordates, but in many it is replaced by the vertebral column. The spongy material (disks) in between the vertebral bones is all that is left of the notochord.

Dorsal Hollow Nerve Cord Dorsal Hollow Nerve Cord. The nerve cord of a chordate embryo is formed from a plate of dorsal ectoderm that rolls up into a tube. It will develop into the chordate's central nervous system . Pharyngeal Pouches/ Gill slits. These paired structures are openings of the upper digestive tube in chordates. The pharynx is the area just behind the mouth. As time progressed the slits became modified to function in gas exchange.

Post anal Tail. Most chordates have a tail extending beyond the anus Post anal Tail. Most chordates have a tail extending beyond the anus. In many aquatic species the tail is equipped with skeletal and muscular tissue for movement.

Figure 30–1 The Generalized Structure of a chordate Muscle segments Tail Anus Pharyngeal pouches Mouth Hollow nerve cord Notochord

Subphyla of Chordata: Subphylum Cephalochordata. Lanclets- small fishlike creatures. Exhibit a closed circulatory system. Subphylum Urochordata. The common organisms are called tunicates. The adults lose 3 of the chordate characteristics as adults: Notochord, nerve chord , and tail. Subphylum Vertebrata. A vertebrate is any chordate that has a backbone.

Cephalization, development of highly specialized sensory structures and a highly specialized brain. One end of the nerve cord becomes the brain. Vertebral column, The axial skeleton (skull, ribs, and vertebra) and the appendicular skeleton (arms and legs, or wings, or flippers) is an internal living system.

Closed circulatory system. It is a closed system Closed circulatory system. It is a closed system. The heart is composed of a collecting chamber(s)-atrium and a pumping chamber(s)-ventricle. The cells of the body exchange food and gases through tiny blood vessels called capillaries. The kidney is the main excretory organ.

Sexes are separate. Fertilization may be internal or external depending on the species. Respiratory organs include the gills, lungs, or highly vascularized skin. Oxygen is carried to all parts of the body in a liquid called blood. Hemoglobin is the main attractant of oxygen and is found in the red blood cells.

jawless, cartilage skeleton, gill slits, no swim bladder Class Main Characteristics Examples Agnatha jawless, cartilage skeleton, gill slits, no swim bladder Lamprey and Hagfish Chondrichthyes Placoid scales, cartilage skeleton internal fertilization, paired fins, Sharks, Rays, and Skates Osteichthyes Bony skeleton, paired fins, operculum, swim bladder Tuna, Bass, Catfish, Flounder Amphibia Smooth skin, no claws, aquatic larvae, breathe through lungs and skin Frogs, Salamanders, and Toads

Class Main Characteristics Examples Reptilia Amniote egg, rough,dry skin, respiration through lungs Snakes, Lizards, Turtles, and crocodiles Aves Feathers, amniote egg, extensive lung system, and wings Birds Mammalia Hair, diaphragm, mammary glands, and bear live offspring. Marsupials, monotremes, and Placentals

30–2 Fishes Fish are aquatic vertebrates that are characterized by: paired fins scales gills.

Evolution of Fishes (1st Vertebrates to evolve) The evolution of jaws and paired fins: Go from prey to predator During the late Cambrian Period

Adaptations to aquatic life Respiration Most fishes exchange gases using gills located on either side of the pharynx. Circulation Fishes have closed circulatory systems with a heart that pumps blood around the body in a single loop.

Adaptations to aquatic life Excretion In the form of ammonia. Wastes diffuse through the gills Others are removed by kidneys Circulation in a Fish In most fishes, the heart consists of four parts: the sinus venosus atrium ventricle bulbus arteriosus

Circulation in a Fish Section 30-2 Gills Brain and head circulation Sinus Venosus Atrium Oxygen-poor blood from the veins collects in the sinus venosus. Blood enters the atrium and flows to the ventricle. Body muscle circulation Digestive system circulation Heart Ventricle Bulbus Arteriosus The ventricle pumps blood into the bulbus arteriosus. The bulbus arteriosus moves blood into the ventral aorta and toward the gills. Oxygen-rich blood Oxygen-poor blood

Response Olfactory bulbs- which are involved with the sense of smell. Cerebrum- is responsible for all voluntary activities of the body. However, in fishes, the cerebrum primarily processes the sense of smell. Cerebellum-coordinates body movements.

Response Medulla oblongata- controls the functioning of many internal organs. Almost all fishes that are active in daylight have well-developed eyes and color vision that is at least as good as yours. Lateral line system. Fishes use this system to sense the motion of other fishes or prey swimming nearby. Swim bladder that adjusts their buoyancy.

Reproduction Oviparous:Lays eggs, externally fertilized, as the embryos of oviparous fishes develop, they obtain food from the yolk in the egg.

Reproduction Ovoviviparous, the eggs stay inside the mother’s body after internal fertilization. Each embryo develops inside its egg, using the yolk for nourishment. The young are then “born alive”.

Reproduction Viviparous- the embryos stay in the mother’s body, as they do in ovoviviparous species. However, these embryos obtain the substances they need directly from the mother’s body. The young of viviparous species are also born alive.

Class Agnatha: Jawless Fish (Lamprey and Hagfish) General Characteristics: Absence of jaws.

These organisms lack paired fins (pelvic and pectoral). Class Agnatha: These organisms lack paired fins (pelvic and pectoral). Skeleton made of cartilage. Round eel-like body with a compressed caudal fin. Soft skin devoid of scales.

Class Agnatha: They lack a swim bladder and gill covers (operculum). The lamprey are parasitic and the hagfish are scavengers. Ectothermic ( animals that cannot control their body temperature).

External fertilization. Oviparous ( egg laying) Lateral line Class Agnatha: External fertilization. Oviparous ( egg laying) Lateral line Two chambered heart Gills used for respiration (gas exchange)

Class Chondrichthyes: Chondrus=Cartilage ( Sharks, Rays, and Skates). General Characteristics: Skeleton made of cartilage. Body covered with triangular Placoid scales.

Class Chondrichthyes: Large caudal fin with the dorsal section larger than the ventral one. Paired fins ( pectoral and pelvic), are stiff and nonflexible. They lack a swim bladder.

Class Chondrichthyes: Ectothermic Internal fertilization. Ovoviviparous ( developing egg kept inside the female for protection and does not live off of the parent). Marine organisms only. Lateral line

Class Chondrichthyes: Two chambered heart Gills used for respiration No external ears No eye lids

Class Osteichthyes: Boney Fish ( Tuna, Carp, Salmon, and Sturgeons). General Characteristics: Skeleton made of bone Lateral line Two chambered heart Operculum covering the gills. Swim bladder

Class Osteichthyes: Ectothermic Paired fins made of rays and spines, or lobed fins lacking the rays and spines. Various types of scales Marine and fresh water species.

Class Osteichthyes: Gills used for respiration External fertilization. Spawning. Oviparous. No external ears No eye lids.