Fishes are vertebrates that have characteristics allowing them to

live and reproduce in water.

Section 1: Fishes

K

What I Know

W

What I Want to Find Out

L

What I Learned

Essential Questions

• What are the features of vertebrates that make them different from

invertebrates?

• What are the characteristics that most fishes have in common?

• How are the characteristics of fishes adapted to aquatic life?

FishesCopyright © McGraw-Hill Education

Review

• notochord

New

• cartilage

• neural crest

• fin

• scale

• operculum

• atrium

• ventricle

• nephron

• lateral line system

• spawning

• swim bladder

FishesCopyright © McGraw-Hill Education

Vocabulary

FishesCopyright © McGraw-Hill Education

Characteristics of Vertebrates

• Animals belonging to subphylum Vertebrata have a vertebral column and

specialized cells that develop from the nerve cord.

• Classes of vertebrates include fishes, amphibians, reptiles, birds, and

mammals.

FishesCopyright © McGraw-Hill Education

Characteristics of Vertebrates

Vertebral column

• The notochord is replaced by a vertebral column that protects and surrounds

the dorsal nerve cord.

• Made of cartilage – flexible tough material found in skeletons, or bone

• The vertebral column functions as a strong, flexible rod that muscles can pull

against during swimming or running.

FishesCopyright © McGraw-Hill Education

Characteristics of Vertebrates

Neural crest

• A neural crest is a group of cells that develop from the nerve cord in

vertebrates.

• Portions of the brain and skull, certain sense organs, and some nerve fibers

are some of the structures that develop from the neural crest.

FishesCopyright © McGraw-Hill Education

Characteristics of Fishes

• Fishes are found in a variety of aquatic habitats including seas, lakes, ponds,

streams, and marshes.

• Most fishes have vertebral columns, jaws, paired fins, scales, gills, and

single-loop blood circulation.

FishesCopyright © McGraw-Hill Education

Characteristics of Fishes

Jaws

• Anterior gill arches evolved into jaws in ancient fishes.

• The development of jaws allowed ancient fishes to prey on a larger range of

animals.

FishesCopyright © McGraw-Hill Education

Characteristics of Fishes

Paired fins

• A fin is a paddle-shaped structure on a fish or other aquatic animal that is

used for balance, steering, and propulsion.

• Paired fins reduce the chance of rolling to the side and allow for better

steering during swimming.

FishesCopyright © McGraw-Hill Education

Characteristics of Fishes

Scales

• Scales are small, flat, platelike structures near the surface of the skin

• Ctenoid scales – made of bone and skin

• Cycloid scales – made of bone and skin

• Placoid scales – made of toothlike material

• Ganoid scales – made of enamel and bone

FishesCopyright © McGraw-Hill Education

Characteristics of Fishes

Gills

• Fishes get oxygen when water that enters their mouths flows across their

gills, where oxygen from the water diffuses into the blood.

• The flow of blood in the gills is opposite the flow of water across the gills,

allowing for more efficient uptake of oxygen

• Some fish protect their gills with operculum, a movable flap.

FishesCopyright © McGraw-Hill Education

Characteristics of Fishes

Circulation

• Vertebrates have a closed circulatory system.

• In most fishes, the heart consists of two main chambers – the atrium, where

the heart receives blood from the body, and the ventricle, where the heart

pumps blood to the gills.

FishesCopyright © McGraw-Hill Education

Characteristics of Fishes

Feeding and digestion

• Ancient fishes were most likely filter feeders and scavengers.

• Most fishes swallow their food whole, passing it through a tube called the

esophagus to the stomach, where digestion begins.

• Fishes and subsequent vertebrates are unable to synthesize certain amino

acids, and must get them from food.

FishesCopyright © McGraw-Hill Education

Characteristics of Fishes

Excretion

• Cellular wastes are filtered from fishes’ blood by the kidneys.

• A nephron is a filtering unit within the kidney that helps maintain the salt and

water balance of the body and to remove cellular waste products from the

blood.

FishesCopyright © McGraw-Hill Education

Characteristics of Fishes

The brain and senses

• Color vision, chemical detection, hearing, and balance are coordinated in the

brain.

• The lateral line system is a sensory system the allows fish to detect

movement in the water, and also helps to keep them upright and balanced.

FishesCopyright © McGraw-Hill Education

Characteristics of Fishes

Reproduction

• The majority of fishes reproduce through external fertilization, but some do

have internal fertilization.

• Male and female fishes release their gametes near each other in the water in

a process called spawning.

• Developing embryos get nutrition from the yolk of their eggs.

• Many fish produce large numbers of eggs and exhibit little care for their

offspring.

FishesCopyright © McGraw-Hill Education

Characteristics of Fishes

Movement

• Most fish have a streamlined shape for moving through water.

• Mucus lubricates their body

• Have a gas-filled space called a swim bladder that allows a fish to control it’s

depth

• Fishes move through the water by contracting muscle groups on either side

of their bodies.

FishesCopyright © McGraw-Hill Education

Review

Essential Questions

• What are the features of vertebrates that make them different from

invertebrates?

• What are the characteristics that most fishes have in common?

• How are the characteristics of fishes adapted to aquatic life?

Vocabulary

• cartilage

• neural crest

• fin

• scale

• operculum

• atrium

• ventricle

• nephron

• lateral line system

• spawning

• swim bladder