25.4 Amphibians

AMPHIBIANS

Sound

25.4 Amphibians

KEY CONCEPT Amphibians evolved from lobe-finned fish.

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Jointed limbs

25.4 Amphibians

Amphibians were the first animals with four limbs and to be able to survive on LAND.

25.4 Amphibians

• First vertebrates to possess true tongues (moisten food)

• First with an outer layer of dead skin to be sloughed off

• First with true ears• First with true voice

box (frogs)• First with a

Jacobson's organ (chemosensory structure)

Amphibian adaptations to live on land

25.4 Amphibians

Amphibians return to the water to reproduce.

•Amphibian eggs are laid in water. •The water is a great environment, it keeps them from drying out, supplies oxygen and removes waste. •In fact, the Greek amphibios means having a double life (water and land)

25.4 Amphibians

Not all eggs are laid in a typical pond however…

• Amphibians use many strategies to keep their eggs wet.– lay eggs directly in water– lay eggs on moist ground– wrap eggs in leaves– brood eggs in pockets

on the female’s back

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25.4 Amphibians

Why not completely terrestrial?

• Reproduction• 3 chambered heart• Inefficient lungs

– Uses skin as accessory breathing organ– Skin must stay moist.

25.4 Amphibians

Characteristics of Amphibians

• Ectothermic• Moist, glandular skin w/o scales or true claws• Three chambered heart• Dependent on water to some degree• Young are different from adult in structure and

appearance (metamorphosis)

25.4 Amphibians

adult frog

young frog

tadpoles

fertilized eggs

• Tadpoles are aquatic larvae of frogs. • During metamorphosis, tadpoles develop into their adult

form.

• Not all amphibians undergo metamorphosis.

25.4 Amphibians

Larva (tadpoles) have many “fish” characteristics

• Gills• 2 chambered heart

25.4 Amphibians

Modern amphibians can be divided into three groups.

• Salamanders (and newts)• Caecilians• Frogs (and toads)

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Salamanders

• Retain tail throughout life• Two pairs of weak legs• Distinct head/neck region• There are over 300 species

of salamanders.

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• Caecilians are legless, burrowing, tropical amphibians.• There are 160 species of caecilians.

• No limbs• Minute eyes

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• Frogs are the largest amphibian group and include toads.• Lack a tail in the adult stage• Head and trunk are fused• Well developed legs

• There are over 3000 species of frogs.

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Difference between frogs and toads?

• All are in the same Order (Anurans)– Includes approx 20 families including the Ranidae

(true frogs) and Bufonidae (true toads).–True toads lack teeth on their upper jaws

–Fire bellied toads are frogs!

25.4 Amphibians

Amphibians around the world are vanishing and may signal danger to our global ecosystem’s health

• One-third of all known amphibian species are threatened with extinction.

• The greatest threats are pollution and climate change, but disease, habitat destruction and fragmentation, and invasive species are also affecting amphibians.

• Amphibians feel the effects of environmental changes long before we do, partly because of their sensitive skin and watery way of life.

Amphibians breathe partly through their skin—taking in vital oxygen. But the permeability that makes their skin special also makes amphibians sensitive to pollution in the soil, air, and water.

25.4 Amphibians

Amphibians around the world are vanishing and may signal danger to our global ecosystem’s health