AMPHIBIANS The Rise of Amphibians (Devonian Period) 360 MYA – Carboniferous period Tetrapod limbs – shoulder/hip girdle – walking on land Lungs for breathing air

AMPHIBIANS Scientific classification Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Class: Amphibia

AMPHIBIANS Orders of Amphibia  Anura- w/out tail – frogs/toads 5,296 species   Caudata- with tail – salamanders/newts 555 species   Gymnophiona –caecilians- naked snake 171 species

AMPHIBIANS Life on land presented new challenges Reason for movement to land – By late Devonian period Climate change caused extinction of many ocean animals and decreased oxygen availability as a result less food available so animals invaded land

Devonian Period

Carboniferous period

a drier habitat Varied food sources Egg laying still required water

Legs - Tetrapod Their circulatory systems became more efficient allowing for more activities.

Tetrapod – 4 for land

AMPHIBIANS Water availability was not reliable. Air temperatures and climate was more variable

AMPHIBIANS New habitats, including vast arrays of plants, insects, necessitated keener sensory (vision, hearing, balance) input. As a result, different regions of the brain further developed.

AMPHIBIANS The word ‘amphibian’ comes from the Greek meaning, “both” (amphi), and bios, meaning, “life”.

ectothermic When we say, ‘cold-blooded’ we mean that the amphibians do not hold or regulate their own body temperature. Their internal body temperature depends on the external environment. They must absorb the warmth of the sun or become sluggish at very cold temperature to maintain bodily heat.

AMPHIBIANS FROG TOAD SALAMANDER

AMPHIBIANS NEWTS CAECILIANS

AMPHIBIANS Most amphibians share 5 key characteristics: 1. Legs – adapted to living on land (frogs, toads, salamanders, newts all have 4 legs) 2. Lungs – larval amphibians have gills, most adult amphibians breathe with a pair of lungs (salamanders are an exception)

AMPHIBIANS 3. Double-loop circulation – two large veins called Pulmonary veins return oxygen-rich blood from the lungs to the heart. Oxygen-rich blood is then pumped to the tissues. 4. Partially divided heart – the atrium of the heart is divided into left and right sides, but the ventricle is not. A mixture of oxygen- rich and oxygen-poor blood is delivered to the tissues.

AMPHIBIANS 5. Cutaneous respiration - besides breathing with their lungs, amphibians take up oxygen through their skin. The skin is usually thin and some- times supplied with glands that produce toxins.

REPTILES & AMPHIBIANS Double-loop circulation in amphibians:

AMPHIBIANS Life Cycle ‘Metamorphosis” of a Tadpoles - herbivores – adult carnivore

AMPHIBIANS Frogs and Toads 1. long hind limbs with powerful muscles allow them to leap into the air. 2. success on land is due in part to: the excellent prey-grasping capability of the tongue attached to the front of the mouth.

AMPHIBIANS 3. Frog skin has mucous glands, poison glands & antibiotics that provide protection against pathogens in an aquatic habitat. 4. Scientists have noticed frog populations on the decline due to increases in parasitic attacks, predation, UV radiation, habitat losses & chemical pollution. Environmental barometer

AMPHIBIANS Frog versus Toad Frog has two bulging eyes strong, long, webbed hind feet that are adapted for leaping and swimming smooth or slimy skin (generally, frogs tend to like moister environments) Frogs tend to lay eggs in clusters.

AMPHIBIANS Frogs versus Toads Toads have stubby bodies with short hind legs (for walking instead of hopping) warty and dry skin (usually preferring dryer climates) paratoid (or poison) glands behind the eyes The chest cartilage of toads is different. Toads tend to lay eggs in long chains.

REPTILES & AMPHIBIANS Salamanders 1. Live in temperate zones & in tropical areas of Central and South America numbering 2. When they walk, the body bends from side to side, much like a fish moving through water.

AMPHIBIANS 3. Adults may retain larval features including gills and tail. 4. Some larvae may become sexually mature but not reach a true adult stage 5. Both forms, larval & adult, are carnivorous.

AMPHIBIANS Caecilians 1. As amphibians evolved they lost their limbs & vision, but not their prey-capturing jaws. 2. These unusual creatures live burrowed in the forest floor where they hunt for invertebrate prey. 3. Most species burrow through the soil, using touch & smell to pursue insects & earthworms. The few aquatic types use electrical cues.