Nonvertebrate Chordates Fishes and Amphibians Chapter 30 30

Nonvertebrate Chordates, Fishes, and Amphibians Chapter 30

30 -1 The Chordates n A chordate is an animal that has, for at least some stage of its life, all of the following… Dorsal hollow nerve cord: runs along the back part of the body with nerves that branch and connect to organs n Notochord: long supporting rod that runs through the body just below the nerve cord n Pharyngeal pouches: found in the pharynx region – may develop into gills n Post anal tail: contains bone and muscle and is used in swimming by aquatic species n

What is a Chordate?

Most Chordates Are Vertebrates n About 96% of all chordates n n are in the subphylum Vertebrata. Most vertebrates have a backbone. The anterior end of the vertebrate backbone develops into a brain. The backbone is made of vertebrae. The backbone is part of an endoskeleton.

Most Chordates are Vertebrates

Nonvertebrate Chordates n The two groups of nonvertebrate chordates are tunicates and lancelets n Both are soft-bodied marine organisms

Tunicates n Tunicates are filter feeders that exhibit all of the chordate characteristics as larva but not as adults

Lancelets n Lancelets are small, fishlike creatures that thrive on the sandy ocean floor n An adult lancelet has a head region that contains a mouth

30 -2 Fishes n Fishes are aquatic vertebrates that are characterized by paired fins, scales, and gills

Evolution of Fishes Doryaspis n The earliest fish were jawless, armored with bony plates (about 400 million yrs ago). n Jaws allowed fish better feeding ability as well as defense. n Paired fins aided movement and provided more control of movement. Pacific Hagfish

The Rise of Modern Fishes n While most early jawed fishes disappeared, they left behind two major groups that continued to evolve and still survive today: Cartilaginous fishes (sharks & rays) n Boney fishes (modern fishes) n

Form & Function in Fishes n Adaptations to aquatic life include various modes of feeding, specialized structures for gas exchange, and paired fins for locomotion

Fish Anatomy

Fish Feeding n Fish can be herbivores, carnivores, parasites, filter feeders, and detritus feeders. n The diagram below highlights some internal organs important during the fish’s digestion

Fish Respiration n Most fishes exchange gases using gills located on either side of the pharynx Oxygen-rich water is pulled in through the mouth and over the gill filaments n Oxygen-poor water is pushed out through the openings in the sides of the pharynx n n Some fishes, including the lungfish, have a lung- like adaptation that allows them to survive in oxygen poor water

Fish Respiration

Fish Circulation n Fishes have closed circulatory systems with well developed heart that pumps blood around the body in a single loop: n. From the heart to the gills n. From the gills to the rest of body n. Back to the heart

Fish Circulation (Heart)

Fish Circulation

Fish Excretion n Fishes rid themselves of nitrogenous wastes in the form of ammonia n Kidneys help fishes control the amount of water in their bodies

Fish Response n Fishes have well-developed nervous systems organized around a brain which has several parts: n n n Olfactory bulb – sense of smell Cerebrum – voluntary activities of body Optic lobe – eye function Cerebellum – coordinates body movement Medulla oblongata – controls internal organ functions Spinal cord n Most fishes can detect gentle currents and vibrations in the water with a sensitive receptor called the lateral line system

Fish Response n Fish have well-developed nervous systems and highly developed sense organs. n The lateral line system can detect gentle currents and vibrations in water with sensitive receptors.

Fish Response n Lateral line system: sensitive receptor system that enables fish to detect gentle currents and vibrations in the water (the 6 th sense)

Fish Movement n The streamlined body shapes of most fishes help to reduce the amount of drag (friction) as they move through the water n Fins assist in movement n Many bony fishes have an internal, gas-filled organ called a swim bladder that adjusts their buoyancy n Because their body tissues are more dense than water, sinking would be an issue without the swim bladder

Fish Movement n The swim bladder is found in bony fish. n The swim bladder is an internal, gas-filled organ that can adjust the buoyancy. It lies just beneath the back bone.

Fish Reproduction n Fishes whose eggs hatch outside the mother’s body are oviparous n As the embryos develop, they obtain food from the yolk in the egg n Fishes whose eggs stay inside the mother’s body are ovoviviparous n Egg yolk is used for nourishment n Fishes whose embryos stay in the mother’s body and get nourishment from the mother are viviparous n These fishes are born alive n (Fish are not viviparous. )

Groups of Fishes n All living fishes can be classified into three groups: n Jawless fishes – have no true teeth or jaws n n Cartilaginous fishes (class Chondrichthyes) – skeletons are built entirely of cartilage, not bone n n Lampreys and hagfishes Sharks, rays, skates Bony fishes (class Osteichthyes) – skeletons are made of hard, calcified bone n Most other fishes

Groups of Fishes n All living fish can be classified into 3 groups: 1. Jawless fish (Agnatha) 2. Cartilaginous Fish (Chondrichthyes) 3. Bony fish (Osteichthyes)

Jawless Fishes n Jawless fish (Class Agnatha) have no true teeth or jaws. n Their skeleton is made of fibers and cartilage. n They lack vertebrae and retain their notochord as adults. n They have fish-like bodies, no scales, and unpaired fins. Hagfish n Two types: Hagfish & Lampreys. Lamprey

Cartilage Fishes n Belong to Class n n Chondrichthyes. Includes sharks, skates, rays. The skeleton is entirely cartilage (no bone). Possess tooth-like scales. Gills are not protected with bony covering.

Bony Fishes n Belong to Class Osteichthyes. n Skeletons are made of bone. n Divided into two groups n Ray-finned fish (have bony spines or rays in the fins) n n n Perch Trout Lobe-finned fish (fleshy fins have bones) n n Trout Lungfish Coelocanth

30 -3 Amphibians n An amphibian is a vertebrate that, with some exceptions, lives in water as a larva and on land as an adult, breathes with lungs as an adult, has moist skin that contains mucus glands, and lacks scales and claws n Amphibian adaptations for life on land include: n Limb bones become stronger n Lungs and breathing tubes n Sternum to protect internal organs

Amphibian Feeding n Tadpoles are filter feeders whereas adult amphibians are carnivorous n Many have long, sticky tongues used to capture insects n Digestion involves food traveling from the mouth down the esophagus into the stomach From the stomach into the small intestine n From the small intestine to the large intestine n From the large intestine into the cloaca (the pathway for waste to leave the body n

Frog Digestive System

Amphibian Respiration n In larval amphibians, gas exchange occurs through the skin and gills n Lungs replace gills in adult amphibians – but some gases continue to diffuse through the skin

Amphibian Circulation n In adult amphibians, the circulatory system forms a double loop 1 st loop carries oxygen-poor blood from the heart to the lungs and skin and takes oxygen-rich blood from the lungs and skin back to the heart n The 2 nd loop transports oxygen-rich blood from the heart to the rest of the body and oxygen-poor blood from the body back to the heart n

Amphibian Circulation

Frog Circulatory & Heart n The amphibian heart has 3 chambers: n Left atrium, right atrium, and ventricle

Amphibian Excretion n Amphibians have kidneys that filter wastes from the blood

Amphibian Reproduction n Amphibian eggs must be kept moist to avoid drying out External fertilization n Eggs are abandoned after the frogs lay them n Offspring metamorphosize from tadpoles into frogs n

Amphibian Movement n Amphibian larvae move like fishes n Adult salamanders have legs that stick out sideways – walking involves moving the body into an S-shaped curve n Frogs and toads have well-developed hind limbs that enable them to jump n Tree frogs have disks on their toes that serve as suction cups for climbing

Amphibian Response n The brain of an amphibian is very similar to that of a fish They have well developed nervous systems n They hear through tympanic membranes (eardrums) located on each side of the head n

Groups of Amphibians n Salamanders have long bodies and tails. Most have four legs. Adults and larvae are carnivores. n Frogs and toads share their ability to jump. Frogs tend to have long legs and jump longer. Frogs are more closely tied to water. Adult frogs and toads lack tails. n Caecilians are legless amphibians that live in water or burrow in moist soil.

Amphibian Concept Map