Chapter 33
Fishes and Amphibians
Section 1: The Fish Body
Section 2: Today’s Fishes
Section 3: Amphibians
Section 1
The Fish Body
Objectives:
•Describe the characteristics of modern fishes.
•Summarize how fish obtain oxygen.
•Summarize how blood circulates through a fish.
•Contrast how marine and freshwater fishes balance
their salt and water content.
•Describe two methods of reproduction in fishes.
Section 1
The Fish Body
Key Characteristics of Modern Fishes
•Features All fishes have gills and a backbone, and they
circulate oxygen-rich blood from their gills directly to
body tissues.
Section 1
The Fish Body
Gills
•Countercurrent Flow Countercurrent flow maximizes
the amount of oxygen that can be extracted from water
through the gills.
Section 1
The Fish Body
Circulation of Blood
•Circulation The four-chambered heart collects oxygenpoor blood from the body and pumps it through the gills
where it receives oxygen. Oxygen-rich blood then
circulates to the rest of the body.
Section 1
The Fish Body
Kidneys
•Salt and Water Balance Fish rely on their gills and a
pair of kidneys to regulate its salt and water balance.
Section 1
The Fish Body
Reproduction
•Reproduction Most fishes fertilize their eggs externally
as males and females release their gametes near one
another in the water.
Section 2
Today’s Fishes
Objectives:
•Distinguish between the three general categories of
modern fishes.
•Describe the major external and internal characteristics
of the yellow perch.
•Summarize features of bony fishes.
Section 2
Today’s Fishes
Jawless Fishes
•Hagfishes and Lampreys Hagfishes and lampreys are
the only surviving jawless fishes.
Section 2
Today’s Fishes
Cartilaginous Fishes
•Sharks Sharks have light, highly streamlined bodies
well suited for rapid swimming, which makes them swift
and efficient predators.
Section 2
Today’s Fishes
Bony Fishes
•Features Bony fishes have an internal skeleton made
completely of bone, a swim bladder, a lateral limb
sensory system, and a set of gill covers called opercula.
•Ray-Finned Bony Fishes Ray-finned bony fishes
comprise the vast majority of living fishes.
•Lobe-Finned Bony Fishes Only seven species of lobefinned fishes survive today.
Section 3
Amphibians
Objectives:
•Summarize the characteristics of modern amphibians.
•Compare the three orders of living amphibians.
•Describe the major external and internal characteristics
of the leopard frog.
Section 3
Amphibians
Key Characteristics of Modern Amphibians
•Features Most amphibians have legs, breathe with
lungs and through their skin, and have two circulatory
loops.
•Lungs An amphibian lung is basically an air sac with a
large surface area for gas exchange.
•Double-Loop Circulation The amphibian heart pumps
oxygen-poor blood to the lungs and receives oxygen-rich
blood from the lungs. The oxygen-rich blood is then
pumped to the body.
Section 3
Amphibians
Frogs and Toads
•Reproduction in Frogs Frogs release their eggs into
water.
Section 3
Amphibians
Salamanders and Caecilians
•Salamanders Salamanders are semiaquatic predators
with tails.
•Caecilians Caecilians are legless amphibians
specialized for burrowing.