homework encyclopedia

FIND OUT MORE. Reproduction 101 • Vertebrates 102

1 FROG AND TOAD

Adult frogs and toads have four

legs and no tail. Although there

is no real scientific difference

between them, frogs are generally

considered to be moist-skinned,

hopping animals and toads

dry-skinned amphibians

that walk.

AMPHIBIAN CLASSIFICATION

• Amphibians are the most
  ancient class of land-living
  vertebrates. They are split
  into three orders.


• Caecilians make up the order
  Apoda. There are around 170
  living species.
  
  
  • The order Urodela contains all
    newts and salamanders. There
    are about 500 species.
  
  
  • The largest order, Anura,
    contains the frogs and toads.
    Altogether, there are around
    5,000 different species.
  
  
  
  

Feathery external gills TADPOLES

still used for breathing

Legs appear

after a few weeks

Tadpole wriggles

out from jelly

Egg with developing

newt tadpole inside

NEWT METAMORPHOSIS 1

Like all amphibians, newts go through a

change in shape known as metamorphosis

as they grow from tadpoles to adults.

Bright colour

warns other

animals that frog

is poisonous

Moist skin

glistens in

the light

Dry skin with bumps

that resemble warts

BLUE POISON-DART FROG 3

Poison-dart frogs are so named

because South American Indians

used their poison to tip blowpipe

darts. One species, the golden

poison-dart frog, carries

enough poison to kill almost

1,000 people.

1 COMMON TOADS SPAWNING
In the breeding season, amphibians gather to spawn (lay jelly-coated
eggs in ponds, ditches, and creeks). They attract their mates using
bright colours, special scents, or loud croaks.

WHAT DO AMPHIBIANS EAT?

All adult amphibians are meat-eating predators.

Their prey include insects, slugs, worms, and even

small mammals, such as mice. Aquatic amphibians eat

water snails, insects, and small fish. Many amphibians

hunt at night, using their keen sight, smell, and

hearing to track victims.

HOW IS COLOUR IMPORTANT TO AMPHIBIANS?

Colour helps amphibians find mates and hide from

predators and prey. Some species are brightly coloured

to tell predators that they are poisonous. Others are

camouflaged to merge in with their surroundings.

WHY DO MOST AMPHIBIANS LIVE NEAR WATER?

The moist skin of most amphibians is not waterproof,

so they live in damp places to prevent them drying

out. Many amphibians lay their soft, jelly-covered

eggs in water, which is known as spawning. Their

young, called. TADPOLES, grow up in the water

and come on to land only when they mature.

Most amphibians hatch as water-dwelling

larvae called tadpoles. With big heads, long

tails, and no limbs, they look more like fish

than amphibians. As they grow older, the

tail shortens and limbs develop. Finally,

they start to resemble miniature adults.

HOW DO TADPOLES BREATHE?

Most tadpoles extract oxygen from fresh water using

internal gills and feathery external gills on their

necks. As they mature, they develop lungs and their

gills normally shrivel up. Unlike their adult forms,

many tadpoles are herbivorous, feeding on plants

which they scrape off pond rocks using rasping teeth.

Gills have

disappeared because

the newt can now

breathe through

its lungs as well

as its skin

COMMON FROG GREEN TOAD

amphibians