1. Fishes, Amphibians, & Reptiles
Chapter 15

2. 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

3. 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.

4. 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.

5. 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.

6. 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

7. 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

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

9. 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

10. 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.

11. 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

12. 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.

13. 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

14. 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

15. 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

16. 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

17. 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.

18. 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

19. 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

20. 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.

21. 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.

22. 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

23. 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

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)

25. 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?

26. 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)

27. 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

28. 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.

29. 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

30. 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.

31. 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

32. 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

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