Nonvertebrate Chordates, Fishes, and Amphibians

Chapter 30

30-1 The Chordates

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

Notochord: long supporting rod that runs through the body just below the nerve cord

Pharyngeal pouches: found in the pharynx region – may develop into gills

Post anal tail: contains bone and muscle and is used in swimming by aquatic species

What is a Chordate?

About 96% of all chordates 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

Most Chordates are Vertebrates

Nonvertebrate Chordates

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

Tunicates

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

Lancelets

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

contains a mouth

30-2 Fishes

Fishes are aquatic vertebrates that are characterized by paired fins, scales, and gills

The earliest fish were jawless, armored with bony plates (about 400 million yrs ago).

Jaws allowed fish better feeding ability as well as defense.

Paired fins aided movement and provided more control of movement.

Doryaspis

Pacific Hagfish

Evolution of Fishes

The Rise of Modern Fishes

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

Form & Function in Fishes

Adaptations to aquatic life include various modes of feeding, specialized structures for gas exchange, and paired fins for locomotion

Fish Anatomy

Fish Feeding

Fish can be herbivores, carnivores, parasites, filter feeders, and detritus feeders.

The diagram below highlights some internal organs important during the fish’s digestion

Fish Respiration

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 Oxygen-poor water is pushed out through the

openings in the sides of the pharynx Some fishes, including the lungfish, have a lung-

like adaptation that allows them to survive in oxygen poor water

Fish Respiration

Fish Circulation

Fishes have closed circulatory systems with well developed heart that pumps blood around the body in a single loop:

From the heart to the gills

From the gills to the rest of body

Back to the heart

Fish Circulation (Heart)

Fish Circulation

Fish Excretion

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

Fish Response

Fishes have well-developed nervous systems organized around a brain which has several parts: 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

Most fishes can detect gentle currents and vibrations in the water with a sensitive receptor called the lateral line system

Fish have well-developed nervous systems and highly developed sense organs.

The lateral line system can detect gentle currents and vibrations in water with sensitive receptors.

Fish Response

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

Fish Response

Fish Movement

The streamlined body shapes of most fishes help to reduce the amount of drag (friction) as they move through the water Fins assist in movement

Many bony fishes have an internal, gas-filled organ called a swim bladder that adjusts their buoyancy Because their body tissues are more dense

than water, sinking would be an issue without the swim bladder

The swim bladder is found in bony fish.

The swim bladder is an internal, gas-filled organ that can adjust the buoyancy. It lies just beneath the back bone.

Fish Movement

Fish Reproduction

Fishes whose eggs hatch outside the mother’s body are oviparous As the embryos develop, they obtain food from

the yolk in the egg Fishes whose eggs stay inside the mother’s

body are ovoviviparous Egg yolk is used for nourishment

Fishes whose embryos stay in the mother’s body and get nourishment from the mother are viviparous These fishes are born alive (Fish are not viviparous.)

Groups of Fishes

All living fishes can be classified into three groups: Jawless fishes – have no true teeth or jaws

Lampreys and hagfishes Cartilaginous fishes (class Chondrichthyes) –

skeletons are built entirely of cartilage, not bone Sharks, rays, skates

Bony fishes (class Osteichthyes) – skeletons are made of hard, calcified bone

Most other fishes

All living fish can be classified into 3 groups: 1. Jawless fish (Agnatha)

2. Cartilaginous Fish (Chondrichthyes)

3. Bony fish (Osteichthyes)

Groups of Fishes

Jawless fish (Class Agnatha) have no true teeth or jaws.

Their skeleton is made of fibers and cartilage.

They lack vertebrae and retain their notochord as adults.

They have fish-like bodies, no scales, and unpaired fins.

Two types: Hagfish & Lampreys.

Lamprey

Hagfish

Jawless Fishes

Belong to Class Chondrichthyes.

Includes sharks, skates, rays.

The skeleton is entirely cartilage (no bone).

Possess tooth-like scales.

Gills are not protected with bony covering.

Cartilage Fishes

Belong to Class Osteichthyes. Skeletons are made of bone. Divided into two groups

Ray-finned fish (have bony spines or rays in the fins)

Perch Trout

Lobe-finned fish (fleshy fins have bones)

Lungfish Coelocanth

Coelocanth

Trout

Bony Fishes

30-3 Amphibians

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

Amphibian adaptations for life on land include: Limb bones become stronger

Lungs and breathing tubes

Sternum to protect internal organs

Amphibian Feeding

Tadpoles are filter feeders whereas adult amphibians are carnivorous Many have long, sticky tongues used to

capture insects Digestion involves food traveling from the

mouth down the esophagus into the stomach From the stomach into the small intestine From the small intestine to the large intestine From the large intestine into the cloaca (the

pathway for waste to leave the body

Frog Digestive System

In larval amphibians, gas exchange occurs through the skin and gills Lungs replace gills in adult amphibians – but some

gases continue to diffuse through the skin

Amphibian Respiration

In adult amphibians, the circulatory system forms a double loop 1st 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

The 2nd 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

Amphibian Circulation

Amphibian Circulation

Frog Circulatory & Heart

The amphibian heart has 3 chambers: Left atrium, right atrium, and ventricle

Amphibians have kidneys that filter wastes from the blood

Amphibian Excretion

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

frogs

Amphibian Reproduction

Amphibian Movement

Amphibian larvae move like fishes

Adult salamanders have legs that stick out sideways – walking involves moving the body into an S-shaped curve

Frogs and toads have well-developed hind limbs that enable them to jump

Tree frogs have disks on their toes that serve as suction cups for climbing

Amphibian Response

The brain of an amphibian is very similar to that of a fish They have well developed nervous systems They hear through tympanic membranes

(eardrums) located on each side of the head

Salamanders have long bodies and tails. Most have four legs. Adults and larvae are carnivores.

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.

Caecilians are legless amphibians that live in water or burrow in moist soil.

Groups of Amphibians

Amphibian Concept Map