Life Cycle of a Fish and a Frog

Fishes and frogs are two kinds of animals that have backbones. They are called vertebrates.

frogs

fishes

Animals with backbones

You have a backbone too. You can feel it in the middle of your back.

Your backbone helps you stand up straight. It also helps you move

and bend.

backbones

Fishes and frogs are alike in another way. They both lay

eggs in or under water.The eggs do not have a hard shell. They have thin coverings and are jellylike. Oxygen from the water passes easily into the egg.

Notice that young fish look very much like the adult. In time, they will grow bigger, but their body shape will stay

the same.eggs

larval fish

fry (until 1 year old)

juvenile

adult

Fish get oxygen from water through their gills.

gills

p. 17Write the stages of the fish life

cycle.1. eggs2. larval fish3. fry4. juvenile5. adult

Frogs belong to a group of animals called amphibians. An amphibian lives

part of its life in water and part on land.

Other examples of amphibians are toads and salamanders.

A frog life cycle begins with an egg.

The young frog that hatches from the egg is called a tadpole.

A tadpole has body parts for living in water. It has a tail for

swimming. It breathes with external gills like fish do.

As the tadpole grows, it develops body parts for living on land. It grows legs. The tail disappears.

Lungs replace gills.

Finally, an adult frog forms. It uses its legs to hop. An adult frog lays

eggs in water. Some frogs reproduce many times before they

die.

p. 19Label the forg life cycle

diagramadult

adult

adult

froglet

adult

tadpole

Tadpole with legs

froglet

eggs

p. 20

Explain Does the tadpole look more

like a fish or its frog parents? Why?

It looks more like a fish because they breathe through gills, swim in the water, have a tail and a mouth like fish do.

Analyze How is the life cycle of a fish

different from the life cycle of a

frog? The life cycle of the fish starts in the water

and they live their whole lives in the water while the life cycle of the frogs start in the water but they live one part in the water and other part on land.

Infer Why does a frog begin its life cycle in

the water and then move onto land?

Because frogs lay the eggs in the water and when they hatch, the tadpoles breathe thorugh gills under water and they also feed on plankton in water.

Analyze What changes may occur in the

frog’s body before it can live on

land?

• The tail disappears.• Lungs replace gills.• It grows legs.