Fishes, Amphibians, & Reptiles Chapter 15

What Are Vertebrates? Section 1 Vertebrates = animals with a backbone Chordates Vertebrates belong to the phylum Chordata. Members of this phylum are called chordates. Chordates all have: Notochord: A stiff but flexible rod that gives the body support. In most vertebrates, the embryo’s notochord disappears & a backbone grows in its place

What Are Vertebrates? Cont. Section 1 What Are Vertebrates? Cont. Hollow nerve cord: runs along the back & is full of fluid. In vertebrates, this nerve cord is called the spinal cord, & it is filled with spinal fluid. Tail: which begins behind the anus. Some chordates have a tail only in the embryo stage Pharyngeal pouches: are found in all chordate embryo. These develop into gills or other body parts as the embryo matures.

Getting a Backbone Section 1 Most chordates are vertebrates. Two that are not are lancelets & tunicates. Vertebrates have: Vertebrae = a segmented column of bones that surrounds & protects the nerve cord also called the backbone a well-developed head protected by a skull The skull & vertebrae are made of either cartilage or bone. Cartilage – the tough flexible material that parts of our ears & noses are made of.

Getting a Backbone: Cont. Section 1 Getting a Backbone: Cont. Vertebrates’ embryo skeletons are made of cartilage as vertebrates grow the cartilage is usually replaced by bone Most vertebrates have skeletons made of bone. Bone fossilizes easily. Many fossils of vertebrates have been discovered. They provide valuable information about the relationship among organisms.

Are Vertebrates Warm or Cold? Section 1 Are Vertebrates Warm or Cold? An animal’s body temperature cannot be too high or too low. Staying Warm Endotherms = Animals that maintain a constant body temperature also called warm-blooded they maintain their body temperature by capturing the heat released by chemical reactions in their cells The chemical reactions that take place in their body cells occur only at certain temperatures But some animals control their body temperature more than others Examples: Birds & mammals

Are Vertebrates Warm or Cold? Cont. Section 1 Are Vertebrates Warm or Cold? Cont. Cold Blood? Ectotherms = their body temperature fluctuates with the temperature of their environment also called coldblooded They do not control their body temperature through the chemical reactions of their cells As they become warm, they also become more active When the temperature drops they slow down Their blood may be warm or cool depending on the external temperature Example: Nearly all fishes, amphibians, & reptiles

What Are Vertebrates? Section 1 How are vertebrates the same as other chordates? How are they different? Explain the difference between endotherms & ectoderms

Section 2 Fishes Fish live in almost every water environment, from shallow ponds & streams to the depths of the oceans. You can find fishes in the cold artic waters & in the warm tropical seas. Fish were the first vertebrates on Earth. They appear in the fossil record about 500 million years ago. Marine & freshwater fishes make up more species than all the other vertebrates combined. There are more than 25,000 species of fishes, and more are being discovered all the time

Fish Characteristics Section 2 Fish have a strong body, well-developed senses, a brain, gills, fins, & a tail. Born to Swim Fish have many body parts that help them swim: Strong muscles attached to the backbone allow fishes to swim vigorously after their prey. Fins = fanlike structures that help fish move, steer, stop, & balance Scales = covering the skin of many fishes; scales protect the body & reduce friction as they swim through water.

Fish Characteristics: Cont. Section 2 Fish Characteristics: Cont. Making Sense of the World Fishes have: well developed vision, hearing, & sense of smell. Most also have a lateral line system. Lateral line system = a row or rows of tiny sense organs along each side of the body that often extend onto the head. (detects water vibrations) a brain that keeps track of all information coming in from these senses a tough skull protects the brain

Fish Characteristics: Cont. Section 2 Fish Characteristics: Cont. Underwater Breathing Fish breathe with gills Gills = organs that remove oxygen from water Oxygen in the water passes through the thin membrane of the gills to the blood. The blood then carries oxygen throughout the body. Gills are also used to remove carbon dioxide from the blood.

Fish Characteristics: Cont. Section 2 Fish Characteristics: Cont. Making More Fish External Fertilization = fertilization of an egg by sperm that occurs outside the body of the female (Most fishes reproduce by external fertilization) The female lays unfertilized eggs in the water, & the male drops sperm on them. Internal Fertilization = fertilization of an egg by a sperm that occurs inside the body of a female In most cases the female then lays eggs that contain the developing embryos. Baby fish hatch from the eggs. But in some species, the embryos develop inside the mother, and the baby fish are born alive

Types of Fishes Section 2 Fishes include five different classes of animals. Two are extinct the other three are: jawless, cartilaginous, & bony Jawless Fishes – These were the first fishes, today there are about 60 different species These fish are eel-like, & have smooth, slimy skin & a round, jawless mouth. Their skeleton is made of cartilage, & they have a notochord but no backbone. These fish have a skull, a brain, & eyes. Modern jawless fishes include lampreys & hagfish

Section 2 Types of Fishes: Cont. Cartilaginous Fishes Have jaws; keen senses; a lateral line system; are strong swimmers; expert predators; & their skin is covered with denticles. Denticles = small, sharp toothlike structures on the skin that give it the feel of sandpaper They have to keep swimming: or these fish sink to the bottom. To stay afloat, these fish, store a lot of oil in their liver but its not enough. to keep water flowing over their gills. If they stop swimming they will suffocate. Sharks, skates, & rays belong to this group In these fishes the skeleton never changes from cartilage to bone. Denticles-smooth in one direction but will cut you in the other

Types of Fishes: Cont. Section 2 Bony Fishes – skeletons made of bone 95% of all fishes are bony fishes Covered by bony scales Swim Bladder = a balloon-like organ that is filled with oxygen & other gases from the bloodstream. (It gives buoyancy) There are two main groups: Ray-finned fishes – have paired fins supported by thin rays of bone. Lobe-finned fishes & lungfishes – have fins that are muscular & thick Goldfish, tuna, trout, catfish, & cod Ray-finned fishes – eels, herrings, trout, minnows, & perch Lobe-finned fishes - coelacanths

Section 2 Fishes Review What are the three types of fishes? Which type are the coelacanths? Most bony fishes reproduce by external fertilization. What does that mean? What is the lateral line system, & what is its function? Compare the ways that cartilaginous fishes & bony fishes maintain buoyancy.

Section 3 Amphibians Vertebrates started in the water then moved but the land had lush green forests, many tasty insects, & few predators. But vertebrates had to adapt to living on land. Most amphibians living on Earth today are frogs or salamanders

Section 3 Moving to Land Had to develop the ability to get oxygen from the air. They developed the lung. Lung = a saclike organ that takes oxygen from the air & delivers it to the blood Their fins became strong enough to support their body weight & eventually became legs Amphibians have to return to the water to keep from drying out, to avoid overheating, & laying their eggs. Most amphibians living on Earth today are frogs or salamanders

Characteristics of Amphibians Section 3 Characteristics of Amphibians Amphibian – “double life” Emerge from the egg they live in the water. Later they develop into animals that can live on land. But even as an adult they are only partly adapted to life on land. They are ectotherms – their body temperature changes according to the temperature of its environment.

Characteristics of Amphibians: Cont. Section 3 Characteristics of Amphibians: Cont. Thin-Skinned most no scales – Skin is thin, smooth, & moist Skin is full of blood vessels which makes it so they can absorb oxygen & water through their skin Can breath by gulping air into their lungs but some only breathe through their skin Skin is so thin & moist, can lose water though their skin & become dehydrated. For this reason most live in water or in damp habitats. Brilliantly colored to warn of poisons May be simply irritating or they may be deadly. dart-poison frog = most deadly Another kind of frog produces a chemical that causes snakes to yawn so when they try to swallow the frog they yawn & the frog jumps out.

Characteristics of Amphibians: Cont. Section 3 Characteristics of Amphibians: Cont. Leading a Double Life Frogs usually reproduce by external fertilization Salamanders reproduce by internal fertilization Their eggs don’t have a shell so the embryos must develop in a very wet environment Tadpole = an aquatic larva Metamorphosis = a change from a larval form to an adult form. Once metamorphosis takes place it is capable of surviving on land Tadpole – can only live in water. It obtains oxygen through gills & uses its long tail to swim. Later the tadpole loses its gills and develops lungs & limbs Page 366 has a picture explaining the metamorphosis of a frog

Kinds of Amphibians Section 3 4,600 species of amphibians that can be broken down into three main groups: Caecilians – 160 species are known Look like snakes but have amphibian skin Found in Asia, Africa, & South America Salamanders – 390 species are known Are most like prehistoric amphibians Found in the woods of North America They eat small invertebrates Picture on page 367 figure 24

Kinds of Amphibians: Cont. Section 3 Kinds of Amphibians: Cont. Frogs & Toads – 90% of amphibians are frogs/toads Found all over the world – deserts to rain forests Toads are a type of frog Highly adapted for life on land Adults have powerful leg muscles for jumping; well-developed ears for hearing; vocal cords for calling; & extendible, sticky tongues, which they use to expertly capture flies & other insects. Vocal sac = a thin sac of skin surrounding their vocal cords (it inflates when they vocalize)

Amphibians Section 3 Describe metamorphosis in amphibians Why do amphibians have to be near water or in a very wet habitat? What adaptations allow amphibians to live on land? Name the three types of amphibians. How are they similar? How are they different?

Section 4 Reptiles About 35 million years after amphibians came out of the water a group of them developed into reptiles. They were the first animals to live completely out of the water. Reptile History Many fascinating reptiles are now extinct. The prehistoric list of reptiles were swimming, flying, turtles, lizards, snakes, & crocodiles Therapsids = were the ancestors of mammals (mammal-like reptiles)

Characteristics of Reptiles Section 4 Characteristics of Reptiles All reptiles use lungs to breathe air. Thick-Skinned A very important adaptation for life on land is thick, dry skin, which forms a watertight layer. Can’t breathe through their skin Coldblooded? Yes, reptiles are ectotherms

Characteristics of Reptiles: Cont. Section 4 Characteristics of Reptiles: Cont. The Amazing Amniotic Egg Amniotic Egg = an egg containing amniotic fluid to protect the developing embryo; usually surrounded by a hard shell The egg provides protection from predators, bacterial infections, & dehydration The amniotic egg is fertilized inside the female. A shell then forms around the egg, and the female lays the egg. In a few cases some have live young.

Types of Reptiles Section 4 6,000 species Turtles & Tortoises – 250 species Only distantly related to the rest of the reptiles The shell makes them unique – it makes them slow so they can out run predators but they can hide Most turtles spend some or all of their time in water (sea turtles) Desert turtles are the exception to this

Types of Reptiles: Cont. Section 4 Types of Reptiles: Cont. Crocodiles & Alligators – 22 species Are all carnivores They eat water bugs, fish, turtles, birds, & mammals Spend most of their time in water Because their eyes & nostrils are on top of their head, they can watch their surroundings while most of their body is hidden underwater.

Types of Reptiles: Cont. Section 4 Types of Reptiles: Cont. Lizards – 4,000 known species Live in deserts, forests, grasslands, & jungles Most lizards eat small invertebrates, but many are herbivores Chameleons, geckos, skinks, & iguanas are some of the amazing variety of lizards

Types of Reptiles: Cont. Section 4 Types of Reptiles: Cont. Snakes – 1,600 known species No legs; snakes move by contractions of their muscular body. Are carnivores – they eat small animals & eggs swallow their prey whole – they have special jaws with five joints that allow them to open their mouths wide and swallow very large prey Can’t see or hear well but can smell extremely well Pythons & boas kill their prey by squeezing it until it suffocates Other snakes have poison glands & special fangs for injecting venom into their prey. The venom kills or stuns the prey & contains powerful enzymes that begin digesting it

Section 4 Reptiles What characteristics set turtles apart from other reptiles? What special adaptations do snakes have for eating?