Overview of Fish and Their Classes

Questions and Answers

Fish are the most numerous and widespread of the vertebrates.

True

How many species of fish are there?

22,000 species

How are the species of fish divided between fresh and saltwater sources?

59% saltwater, 40% freshwater, 1% in both

What are the three classes of fish?

Class Agnatha, Class Chondrichthyes, and Class Osteichthyes Signup and view all the answers

What is another name for Class Agnatha?

jawless fish Signup and view all the answers

What are the characteristics of Class Agnatha?

slimy skin, unpaired fins, soft eel-like bodies, notochord, cartilaginous skeleton Signup and view all the answers

What two species are under Class Agnatha, and how many species of each are there?

lampreys and hagfish; 70 species Signup and view all the answers

Describe the lamprey.

damages commercial fisheries (Great Lakes mostly), spawns in streams, larval stage lives in streams for several years before metamorphosing into adults, mouth sucker-like with hard teeth, tears hole and sucks out blood of its prey, parasitic form of feeding Signup and view all the answers

Describe the hagfish.

bottom dwellers, scavengers, mouth surrounded by fleshy tentacles 'feelers' equipped with a row of tooth-like plates, tears flesh of prey Signup and view all the answers

What is another word for Chondrichthyes?

cartilaginous fish Signup and view all the answers

What animals are included in this class?

sharks, skates, and rays Signup and view all the answers

What are their bones made of?

cartilage Signup and view all the answers

What are the two advantages of Chondrichthyes over Agnatha?

biting jaws, paired fins (stabilization) Signup and view all the answers

The largest shark, the whale shark, is a carnivore.

False Signup and view all the answers

What do most sharks prey on?

carnivores, other fish or bottom dwelling animals (mollusks and lobsters) Signup and view all the answers

Describe the shark.

streamlined body + paired fins = maneuverability and stability, paired gills efficient structure for O2 and CO2 exchange, sharp, triangular teeth capture and tear prey apart, teeth can be repeatedly shed and replaced, paired nostrils connect to sensitive olfactory organs, lateral line detects movement in the water, covered in placoid scales Signup and view all the answers

What is a lateral line?

a series of pits along the side of the body, line of sensory cells along each side of the body Signup and view all the answers

What is a placoid?

cone-like scales with a sandpaper texture, composed of dentin, within a pulp cavity Signup and view all the answers

Male and female sharks remain separate.

True Signup and view all the answers

Describe fertilization in its barest details. How many young are produced? Are they dependent?

internal fertilization; 2 to 60 young; young fully formed and independent Signup and view all the answers

What makes skates and rays similar to each other but not sharks? Describe them.

flattened bodies, accustomed to living on the bottom, enlarged pectoral fins extending on both sides of the head, often bury their mouth in the ocean bottom, take in water through modified gill slits called spiracles Signup and view all the answers

What is another name for Class Osteichthyes?

bony fish Signup and view all the answers

They are the most numerous species among the fish.

True Signup and view all the answers

What are some examples of species in Osteichthyes?

trout, salmon, cod, perch, sole, eel, halibut, and salmon Signup and view all the answers

What are the three sub-classes of Osteichthyes?

ray-finned fish, lungfish, and lobe-finned fish Signup and view all the answers

What subclass do the fish cod and perch belong to?

ray-finned fish Signup and view all the answers

What are some characteristics of ray-finned fish?

wide range of diversity, live in almost all aquatic habitats, gills in a common chamber protected by an operculum, surface covered with flat, flexible scales, 2 chambered heart Signup and view all the answers

What is the operculum?

a bony plate covering the gill chamber of the ray-finned fish Signup and view all the answers

Where does fertilization occur in fish?

external Signup and view all the answers

How does fertilization occur in fish?

female deposits numerous eggs, then male deposits milt over these eggs Signup and view all the answers

What is milt?

sperm-laden fluid Signup and view all the answers

Study Notes

Overview of Fish

Fish are the most numerous and widespread vertebrates.
There are approximately 22,000 species of fish.
Distribution: 59% saltwater, 40% freshwater, 1% inhabit both environments.

Classes of Fish

Three primary classes:
- Class Agnatha (jawless fish)
- Class Chondrichthyes (cartilaginous fish)
- Class Osteichthyes (bony fish)

Class Agnatha

Characteristics:
- Slimy skin, unpaired fins, and eel-like bodies.
- Possess a notochord and a cartilaginous skeleton.
Major species:
- Lampreys and hagfish, totaling approximately 70 species.

Lampreys

Feed parasitically using a sucker-like mouth with hard teeth to extract blood from prey.
Damage commercial fisheries, especially in the Great Lakes.
Larval stage lives in streams for several years before metamorphosing into adults.

Hagfish

Dwell on the ocean floor and are scavengers.
Mouth has fleshy tentacles and rows of tooth-like plates for tearing flesh.

Class Chondrichthyes

Composed of sharks, skates, and rays.
Bones are made of cartilage.
Advantages over Agnatha:
- Possess biting jaws and paired fins, allowing for better stabilization.

Sharks

Are carnivorous and prey on fish and bottom-dwelling animals.
Features:
- Streamlined bodies and paired fins enhance maneuverability and stability.
- Paired gills facilitate efficient gas exchange.
- Equipped with sharp, triangular teeth that can be continually replaced.
- Lateral line system detects movement and vibrations in the water.

Reproduction in Sharks

Males and females are generally separate, meeting only for mating.
Internal fertilization occurs, producing 2 to 60 fully formed, independent young.

Skates and Rays

Similar to sharks but have flattened bodies and enlarged pectoral fins.
Often bury their mouths in the sediment and take in water through spiracles.

Class Osteichthyes

Known as bony fish and represent the most numerous fish species.
Examples include trout, salmon, cod, perch, sole, eel, and halibut.
Three sub-classes:
- Ray-finned fish
- Lungfish
- Lobe-finned fish

Ray-Finned Fish

Exhibit a wide diversity, found in nearly all aquatic habitats.
Their gills are protected by an operculum, a bony plate.
Possess a two-chambered heart and flat, flexible scales covering their bodies.

Reproductive Process

Fertilization occurs externally:
- Females lay numerous eggs, and males deposit milt, a sperm-laden fluid, over them.

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Description

Explore the fascinating world of fish, the most numerous vertebrates with around 22,000 species. This quiz covers their distribution, primary classes including Agnatha, Chondrichthyes, and Osteichthyes, as well as specific features and examples of jawless fish like lampreys and hagfish.