Download Chapter 16: Fishes, Amphibians, and Reptiles

Chapter 16: Fishes, Amphibians, and Reptiles
SECTION 1
We have learned about animals without backbones, now we are going to turn our
attention to animals with backbones. Animals with a backbone are called vertebrates.
Vertebrates belong in the phylum Chordata. We call these organisms’ chordates.
Vertebrates make up the largest group of chordates, but two groups (the lancelets and
tunicates) do not have a backbone. The reason they are chordates is because they have a
notochord (hollow nerve cord), pharyngeal pouches, and a tail at some point in their
development.
The lancelets and tunicates are primitive chordates that live in marine ecosystems.
Organisms with a Backbone
The bones that make up the “backbone” are called vertebrae. The vertebrae cover the
nerve cord for protection. The vertebrae have a hole (called a foramen) the nerve cord
passes through. Vertebrates also have a head that is well protected by a skull. The skull
and vertebrae are made of bone or cartilage. Cartilage is a connective tissue that is tough
and flexible. Bones on the other hand are not flexible. Bone is very hard and can be
fossilized easily.
Endotherm or Ectotherm?
Endotherm organisms produce their own heat for their body. Endo means within, therm
means temperature. So, Endotherm means the temperature comes from within.
Remember cellular respiration creates heat and the body of endotherms captures the heat
to maintain a constant temperature. Endotherms are also called warm-blooded. Due to the
fact that endotherms maintain a constant body temperature, they are capable of living in
cold environments. Examples of endotherms: birds, deer, bears, cats, dogs, wolves, mice,
and humans (these are only a few).
Ectotherm organisms are those that rely on the environment to supply their heat and
maintain their body temperature. Ectotherms are also called cold-blooded organisms.
Ectotherms examples include fish, reptiles (snakes, lizards), and amphibians (frogs and
salamanders).
SECTION 1 Continued
Fishes
Fish are vertebrates and ectothermic organisms. Some fish are predators, and others are
prey. Fish must search for their food so they are consumers. They have a brain and
nervous tissues. Fish have fins, which are thin structures that help them to swim. Most
fish also have scales on the surface of their skin for protection and reducing friction when
they swim.
The Senses of Fish
Fish pick up vibrations and noises through an organ called a lateral line. The lateral line
extends down the side of the fish from head to tail. The lateral line can help fish pick up
vibrations given off by prey and if they are a prey species, they can detect the vibrations
of predators.
Fish breathe though their gills. The anatomy of the gills is such that dissolved oxygen in
the water can diffuse into the fish’s bloodstream. This same process (diffusion) also rids
the fish’s body of carbon dioxide.
The majority of fish have external fertilization in which the female deposits the eggs into
a nest in the water or simply into the water and the male releases sperm and the sperm
and egg unite (fertilization) outside of the male and female fish. A few fish have internal
fertilization in which the male deposits the sperm inside the female. Fish that carry out
internal fertilization usually give live birth to their young. Example of live birth from fish
is the common molly many people have in their home aquarium.
Types of Fishes
There are several types of fishes. One group has bones that make up their skeleton and
another group has cartilage instead of bones and yet another group is called jawless fish.
Jawless fish do not have jaws. This group includes lampreys and hagfish. They resemble
eels and have smooth, slimy skin. Their mouth is round and they attach to other fish and
feed like a parasite on the nutrients from their host. They have a notochord, but do not
have a backbone. They have a skull, brain and eyes.
Cartilaginous Fishes. Examples of this type of fish include sharks, skates, and rays.
During their development from embryo to adult, their cartilage is not replaced by bone,
but remains cartilage all of their life. These fish have a notochord and keen sense of smell
and vision. They also have a lateral line system also. The skin of cartilaginous fish is
covered with denticles which make the skin feel sandpapery if you run your hand from
tail to head. If you fell of it from head to tail, the skin feels smooth. Some cartilaginous
fish must swim all the time to keep water flowing across their gills or they will suffocate
if they stop swimming. There is one cartilaginous fish called the paddlefish that live in
freshwater in our area.
Bony Fishes. You are probably more familiar with bony fishes because most freshwater
fish are bony fish. Examples include bluegill, bass, catfish, perch, goldfish and many
other aquarium fish. These fish have bones for their skeleton as the name implies. Bony
fish have the ability to remain in one place without swimming because they have a swim
bladder (a balloon like organ filled with air). The swim bladder gives the fish buoyancy
(the ability to float in water).
There are two groups of bony fish named due to the type of fins they have. One group is
ray finned fish. Ray finned fish are the most common and they have paired fins that are
supported by bones. The second group is called lobe finned fish, which have fins that are
thick and supported by muscles. The lobe finned fish are considered representatives of
ancient fish.
SECTION 2 AMPHIBIANS
The majority of amphibians today are frogs and salamanders. Early examples or ancient
amphibians looked a lot different from what we know as amphibians today. The unique
feature of amphibians is the lung. This enables them to be land dwellers at times. They
are capable of leaving the water and they breathe atmospheric air. Their skin must remain
moist so they can not be away from moist environments for long periods at a time.
Amphibian Characteristics. Amphibian means “double life”. This refers to the fact that
they must develop in wet environments, but as adults they are partially adapted to life on
land. They must always live near water or moist areas. Most amphibians do not have
scales, but they have smooth and slick skin. The organisms that make up amphibians are
found in a wide range of colors. Many of the brightest colored amphibians are poisonous
(like the poison dart frogs). Amphibians are unique because they have lungs, but they can
also absorb oxygen through their skin because their skin is very thin and full of blood
vessels.
The embryo of amphibians usually develops into a tadpole, which must live in water or
very wet conditions. As the tadpole develops, they lose their tail and develop legs. The
process of changing from the tadpole to the adult form is known as metamorphosis. A
few of the frogs do not form a tadpole, but develop into frogs from the embryo stage.
Kinds of Amphibians. There are three groups, 1) caecilians, 2) salamanders, and 3) frogs
and toads.
Caecilians are legless amphibians and many people are not familiar with these organisms.
Caecilians live in tropical areas.
Salamanders – these are considered the most prehistoric amphibians. Salamanders eat
small invertebrates. They survive in wet areas and many are colorful.
Frogs and Toads – This is the largest group of amphibians. They are found all over the
world and in almost all environments. Frogs tend to have a more moist skin and toads are
well adapted to dry climates. These organisms have a tongue that “flips” out and is sticky
on the tip. The frogs and toads feed on insects. Many frogs and toads are capable of
“singing” because they have vocal cords. The majority of their singing occurs when they
are searching for mates.
All amphibians are environmental indicators because their skin is thin and they are
sensitive to changes in their ecosystem. Many scientists are studying amphibians to
determine what a “healthy” environment should be. If scientists notice problems in
amphibian populations, there is a very good chance that some factor in the ecosystem
causing the problem.
SECTION 3 REPTILES
Many scientists believe that reptiles were the first animals to live out of the water and on
dry land. Many also believe that there was a group called Therapsids that were the
ancestors to the mammals.
Characteristics of Reptiles. Reptiles have thick skin and this serves as protection from
their cells from drying out. Reptiles have lungs that enable them to survive on land.
Reptiles are cold blooded (ectothermic) and become active as the environment they
survive within warms up. As the environment cools down, their metabolism slows down.
Reptiles have an amniotic egg, which means it is an egg surrounded by a shell. The shell
prevents the embryo from drying out. The reptile egg has yolk (food for embryo),
albumin (protein source for the developing embryo), amniotic sac (surrounds the embryo
and protects it from injury because the fluid inside act as a shock absorber), and the shell.
Most reptiles have internal fertilization and the shell develops around the egg and then
the female lays the egg. Many lay their eggs and bury them under decomposing
vegetation, which incubates the eggs as it decomposes (remember that heat is generated
as material decomposes.)
Examples of Reptiles: Turtles, snakes, lizards, alligators, and crocodiles. Most turtles live
their life near or in water, yet they have lungs to breathe air from the atmosphere. Turtles
eat many invertebrates and some capture vertebrates as food sources. Crocodiles and
alligators are carnivores (meat-eaters) and are effective predators and live in association
to water sources. Lizards are found in most environments, and feed on insects,
invertebrates and a few feed on vertebrates. Also, many lizards are herbivores. Snakes are
carnivores, and many will consume eggs out of nests when they have the opportunity.
Snakes swallow their food whole and have a jaw that can “unhinge” in order for their
mouth to open wider and swallow their prey. Snakes have forked tongues and they have a
organ that detects heat. When they have their tongue out they are taking a sample of the
air because molecules will stick to the tongue and then taken into their mouth to the organ
of sense. The organ is called the Jacobson’s organ.
SECTION 1 STUDY GUIDE
1. Animals with a backbone are called ______________________.
2. Vertebrates belong in the phylum ______________________.
3. The two groups of chordates that do not have a backbone are the ____________
and the __________________.
4. The presence of a _______________________ is what gives chordates their
phylum.
5. ____________________ organisms produce their own heat from within their
body.
6. ____________________ organisms rely on the temperature of the environment
they are in to regulate their temperature. (Also called cold blooded.)
SECTION 1 Continued STUDY GUIDE
1.
2.
3.
4.
5.
Fish are vertebrates and __________________ organisms.
Fish must search for their food, this makes them __________________.
Fish sense vibrations through their _________________ line.
Fish obtain oxygen through their __________________ by diffusion.
The majority of fishes carry out ____________________ fertilization for
reproduction purposes.
6. Fish that carry out ___________________ fertilization give live birth.
7. One type of fish that have bones are _______________ fish, while those that have
cartilage are called ____________________ fish and those without jaws are
called _____________________ fish.
8. Sharks, rays and skates have ____________________ on their skin surface and
that is why they feel sandpapery if you rub your fingers down them from tail to
head.
9. Bony fish have a _________________ bladder that gives them buoyancy.
10. There are two types of finned fish which are _________________ finned fish and
______________________ finned fish.
SECTION 2 STUDY GUIDE
1. The majority of amphibians are _______________ and ____________________.
2. The three groups of amphibians are ______________________,
___________________________ and ______________________.
3. The legless amphibians found in the tropics are called _____________________.
4. _________________________ are considered the most ancient amphibians.
5. The largest group of amphibians is ______________ and ________________.
6. When amphibians change from the tadpole to the adult stage, they go through the
process known as _______________________.
7. Frogs have ___________________ ________________ that allows them to
“sing” or call for mates.
8. Amphibians are environmental _____________________ because their skin is so
thin and they are very sensitive to changes in the environment.
SECTION 3 STUDY GUIDE
1. Many scientists believe that _________________ were the first animals to live
out of water and on dry land.
2. Reptiles have _________________ skin that helps protect them from drying out.
3. Reptiles have a _____________________ egg, which means it is covered or
surrounded by a shell.
4. Most reptiles have _________________ fertilization, and many lay elongated
eggs. The poisonous snakes in our geographical area give live birth.
5. Many reptiles rely on ____________________ organic material to incubate their
eggs.
6. Snakes have _____________________ tongues that they sample the air with and
then insert their tongue into the _____________________ organ to “sense” their
surroundings.
7. Snakes are ____________________, which means they are meat eaters.
8. The _______________ of the egg serves as food for the developing embryo.
9. Reptile body temperature is directly related to the temperature of the current
temperature. This means they are _______________________ or cold blooded.
10. In order for snakes to eat larger animals that normal, their jaws have the capability
to _____________________.
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