Amphibians

Section 30.2

Animal Classification

Animals

Invertebrates

Vertebrates

SpongesCnidariansWormsMollusksArthropodsEchinoderms

Ectotherms(cold-blooded)

Endotherms(warm-blooded)

FishesAmphibiansReptiles

BirdsMammals

Amphibians

- Order Anura- Order Caudata- Order Apoda

Phylum Chordata

What is an Amphibian?

Class Amphibia – means “double life” Starts life in water and changes on land

Evolutionary advantages over fishes Thin, moist skin Most amphibians have four legs Lungs

What is an Amphibian?

Nearly all amphibians rely on water for reproduction

Undergo external fertilization Water is needed to transport sperm

Ectotherms

Ectotherm – an animal that has a variable body temperature and gets its heat from external sources (can’t regulate their body temperature on their own)

Ectotherms

Amphibians become dormant in regions that are too hot or cold for part of the year Many of them burrow into mud and stay there until

suitable conditions return

Metamorphosis

Tadpoles possess fins, gills, and a two-chambered heart as seen in fish

Tadpoles develop legs, lungs, and a three-chambered heart to become adults

Metamorphosis

Young salamanders resemble adults, and they have gills and usually have a tail fin

Most adult salamanders lack gills and fins Adult salamanders have no lungs and breathe

only through their skin

Walking Requires More Energy The evolution of the three-chambered heart

in amphibians ensured that cells received the proper amount of oxygen

Walking Requires More Energy One chamber receives oxygen-rich blood

from the lungs and skin Another chamber receives oxygen-poor blood

from the body tissues Blood from both chambers then moves to the

third chamber which mixes the two types of blood

Walking Requires More Energy Because of the mixture of blood, the skin is

much more important than the lungs as an organ for gas exchange

Walking Requires More Energy Because the skin of an amphibian must stay

moist to exchange gases, most amphibians are limited to life on the water’s edge or other moist areas

Frogs and Toads

Frogs and toads belong to the order Anura Frogs have long hind legs and smooth, moist

skin Toads have short legs and bumpy, thick, dry

skin

Frogs and Toads

Adult frogs and toads are predators that eat invertebrates, such as insects and worms

Many species of frogs and toads secrete chemicals through their skin as a defense against predators

Frog eating bird

Frogs and Toads

Frogs and toads also have vocal cords Vocal cords – sound-producing bands of tissue in

the throat As air moves over the vocal cords, they

vibrate and cause molecules in the air to vibrate

Frogs and Toads

Tympanic membrane – amplifies sounds frogs and toads make

Throat pouches and tympanic membranes increase the loudness of their calls

Frogs and Toads

Frogs and toads are among the first organisms to be exposed to pollutants in the air, on land, or in the water

Declining numbers of frogs species sometimes indicate the presence of pollutants in the environment

Salamanders

A salamander (order Caudata) has a long, slender body with a neck and tail

Salamanders resemble lizards, but have smooth, moist skin and lack claws

Salamanders

The young hatch from eggs, look like small salamander adults, and are carnivorous

Caecilians

Caecilians (order Apoda) are burrowing amphibians, have no limbs, and have a short (or no) tail

They are tropical animals with small eyes that often are blind

Caecilians

They eat earthworms and other invertebrates found in the soil

All caecilians have internal fertilization

Challenges of Life on Land

Some dangers living on land 1. Temperature of water remain fairly constant

while air temperatures can vary greatly

Challenges of Life on Land

2. Without the support of water, the body was clumsy and heavy

The legs of a salamander are set at right angles to the body. This prevent the belly from dragging on the ground.

Challenges of Life on Land

Raised trunks from the ground increases mobility