1. 30.1 Section Objectives – page 793
Relate the structural adaptations of fishes to their environments.
Compare and contrast the characteristics of the different groups of fishes.
Interpret the phylogeny of fishes.
30.1 Section Objectives – page 793

2. Section 30.1 Summary – pages 793-802
What is a fish?
Fishes, like all vertebrates, are classified in the phylum Chordata.
Fishes belong to the subphylum Vertebrata.
Section 30.1 Summary – pages

3. Section 30.1 Summary – pages 793-802
What is a fish?
In addition to fishes, subphylum Vertebrata includes amphibians, reptiles, birds, and mammals.
Section 30.1 Summary – pages

4. Section 30.1 Summary – pages 793-802
What is a fish?
In vertebrates, the embryo’s notochord is replaced by a backbone in adult animals.
All vertebrates are bilaterally symmetrical, coelomates that have endoskeletons, closed circulatory systems, nervous systems with complex brains and sense organs, and efficient respiratory systems.
Section 30.1 Summary – pages

5. Section 30.1 Summary – pages 793-802
Classes of fishes
Fishes
Class
Organisms
Characteristics
Jawless, cartilaginous
skeleton, gills
Myxini
Hagfishes
Jawless, cartilaginous
skeleton, gills
Cephalaspidomorphi
Lampreys
Jaws, cartilaginous skeleton, paired
fins, gills, scales, internal fertilization
Chondrichthyes
Sharks, skates, rays
Jaws, bony skeleton, paired fins,
gills, scales, swim bladder
Osteichthyes
Lobe-finned fishes,
ray-finned fishes
Section 30.1 Summary – pages

6. Section 30.1 Summary – pages 793-802
Fishes breathe using gills
Fishes have gills made up of feathery gill filaments that contain tiny blood vessels.
Gill Filaments
Section 30.1 Summary – pages

7. Section 30.1 Summary – pages 793-802
Fishes breathe using gills
As a fish takes water in through its mouth, water passes over the gills and then out through slits at the side of the fish.
Gill Filaments
Capillary networks
in filament
Water
Gill
filaments
Artery
Vein
Water
Section 30.1 Summary – pages

8. Section 30.1 Summary – pages 793-802
Fishes breathe using gills
Oxygen and carbon dioxide are exchanged through the capillaries in the gill filaments.
Gill Filaments
Capillary networks
in filament
Water
Gill
filaments
Artery
Vein
Water
Section 30.1 Summary – pages

9. Section 30.1 Summary – pages 793-802
Fishes have two-chambered hearts
Aorta
Capillary
network
Gills
Heart
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10. Section 30.1 Summary – pages 793-802
Fishes reproduce sexually
Although the method may vary, all fishes reproduce sexually.
Fertilization and development is external in most fishes.
Eggs and sperm can be released directly into the water, or deposited in more protected areas, such as on floating aquatic plants.
Section 30.1 Summary – pages

11. Section 30.1 Summary – pages 793-802
Fishes reproduce sexually
Most bony fishes have external fertilization and development.
This type of external reproduction in fishes and some other animals is called spawning.
Salmon spawning
Section 30.1 Summary – pages

12. Section 30.1 Summary – pages 793-802
Fishes reproduce sexually
In some bony fishes, such as guppies and mollies, fertilization and development is internal.
Most fishes that produce millions of eggs provide no care for their offspring after spawning.
Some fishes, such as the mouth-brooding cichlids, stay with their young after they hatch.
Section 30.1 Summary – pages

13. Section 30.1 Summary – pages 793-802
Most fishes have paired fins
Fishes in the classes Chondrichthyes and Osteichthyes have paired fins.
Fins are fan-shaped membranes that are used for balance, swimming, and steering.
Section 30.1 Summary – pages

14. Section 30.1 Summary – pages 793-802
Most fishes have paired fins
Fins are attached to and supported by the endoskeleton and are important in locomotion.
Section 30.1 Summary – pages

15. Section 30.1 Summary – pages 793-802
Most fishes have paired fins
The paired fins of fishes foreshadowed the development of limbs for movement on land and ultimately of wings for flying.
Dorsal
fins
Pectoral
fin
Anal
fin
Caudal
fin
Pelvic
fins
Section 30.1 Summary – pages

16. Section 30.1 Summary – pages 793-802
Fishes have developed sensory systems
Cartilaginous and bony fishes have an adaptation called the lateral line system that enables them to sense objects and changes in their environment.
Lateral line
Gelatin-like fluid
Receptor cells
Nerve
Section 30.1 Summary – pages

17. Section 30.1 Summary – pages 793-802
Fishes have developed sensory systems
The lateral line system is a line of fluid-filled canals running along the sides of a fish that enable it to detect movement and vibrations in the water.
Lateral line
Gelatin-like fluid
Receptor cells
Nerve
Section 30.1 Summary – pages

18. Section 30.1 Summary – pages 793-802
Fishes have developed sensory systems
Fishes have eyes that allow them to see objects and contrasts between light and dark in the water as well.
Section 30.1 Summary – pages

19. Section 30.1 Summary – pages 793-802
Fishes have developed sensory systems
Some fishes that live in areas of the ocean where there is no light may have reduced, almost nonfunctional eyes.
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20. Section 30.1 Summary – pages 793-802
Fishes have developed sensory systems
Some fishes also have an extremely sensitive sense of smell and can detect small amounts of chemicals in the water.
Sharks can follow a trail of blood through the water for several hundred meters.
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21. Section 30.1 Summary – pages 793-802
Most fishes have scales
Scales are thin bony plates formed from the skin.
Scales can be toothlike, diamond-shaped, cone-shaped, or round. Shark scales are similar to teeth found in other vertebrates.
Section 30.1 Summary – pages

22. Types of Scales
Cycloid Scales: have a smooth outer edge, and are most common on fish with soft fin rays, such as salmon
Ctenoid Scales: have a toothed outer edge, and are usually found on fish with spiny fin rays, such as bass and crappie
Placoid Scales: are found on cartilaginous fish including sharks.
Ganoid Scales: can be found on Gars. They have a diamond-shaped, shiny, and hard scale.

23. Section 30.1 Summary – pages 793-802
Jaws evolved in fishes
Gill arches
Gill slits
Jawless, filter-feeding fish
Jaws
Skull
Gill slits
Gill arches
Beginning of jaw formation
Fish with jaws
The advantage of jaws is that they enable an animal to grasp and crush its prey with great force.
Section 30.1 Summary – pages

24. Section 30.1 Summary – pages 793-802
Jaws evolved in fishes
Gill arches
Gill slits
Jawless, filter-feeding fish
Jaws
Skull
Gill slits
Gill arches
Beginning of jaw formation
Fish with jaws
Jaws also allowed early fishes to prey on a greater variety of organisms.
Section 30.1 Summary – pages

25. Section 30.1 Summary – pages 793-802
Most fishes have bony skeletons
Bony fishes, a successful and widely distributed class, differ greatly in habitat, size, feeding behavior, and shape.
Section 30.1 Summary – pages

26. Section 30.1 Summary – pages 793-802
Bony fishes have separate vertebrae
that provide flexibility
A mackerel flexes
the posterior end
of its body to
accentuate the tail
-fin movement.
A tuna keeps its body
rigid, moving only its
powerful tail. Fishes
that use this method
move faster than all
others.
An eel moves its
entire body in an
S-shaped pattern.
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27. Section 30.1 Summary – pages 793-802
Bony fishes evolved swim bladders
Swim bladder
A fish with a swim bladder can control its depth by regulating the amount of gas in the bladder.
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28. Section 30.1 Summary – pages 793-802
Bony fishes evolved swim bladders
Some fishes remove gases from the swim bladder by expelling them through a special duct that attaches the swim bladder to the esophagus.
In fishes that do not have this duct their swim bladders empty when gases diffuse back into the blood.
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29. Section 30.1 Summary – pages 793-802
A Bony Fish
Lateral line system
Swim bladder
Kidney
Scales
Urinary bladder
Reproductive organ
Fins
Stomach
Intestine
Liver
Heart
Gills
Section 30.1 Summary – pages

30. Summary of Ray-Finned Fishes
Class Actinopterygii (Ray-finned fishes) Skeleton made of bone. Scales can be ganoid, cycloid, ctenoid or absent. Paired and median fins present. Jaws present. Teeth usually present with enamaloid covering. Respiration by gills and covered with an operculum. Swim bladder often present with or without a duct connecting to esophagus. Two chambered heart. Sexes usually separate. Fertilization usually external. Nervous system of a brain with small cerebrum, optic lobes, and cerebellum.

31. Summary of Lobe-Finned fishes
Class Sarcopterygii (Lobe-finned fishes) Skeleton made of bone. Paired and median fins present. Jaws present, teeth are covered with true enamel and typically are crushing plates restricted to palate. Gills supported by bony arches and covered by an operculum. Swim bladder vascularized and used for respiration and buoyancy. Nervous system with a cerebrum, cerebellum, and optic lobe. Sexes separate; fertilization external or internal.