Presentation on theme: "REPTILES & AMPHIBIANS The Rise of Amphibians (Devonian Period)"— Presentation transcript:
1 REPTILES & AMPHIBIANS The Rise of Amphibians (Devonian Period) A. Amphibians have a body plan and mode reproduction somewhere between“fishes” and “reptiles.”They are vertebrates with a bonyendoskeleton and a four-legged aquaticancestor.
2 REPTILES & AMPHIBIANSThe 4 classes of terrestrial (tetrapods) vertebrates:AmphibiansReptilesBirdsMammals
4 REPTILES & AMPHIBIANS Subclasses and Orders of Amphibians Order Temnospondyli- extinct Subclass Lepospondyli- extinct Subclass Lissamphibia Orders Anura Caudata Gymnophiona
5 REPTILES & AMPHIBIANS1. Life on land presented new challenges to the emerging amphibians.The idea here is that asteroids that hitearth caused the mass extinction ofmarine life and affected much of theavailable O2 at the sea’s surface. Sincethe tetrapods had lungs they could takeadvantage of gulping air while spendingsome of their time on land.
6 REPTILES & AMPHIBIANS Scientists say no significant genetic change would be required to make thetransaction from lobed fins to limbs.They contend that even a singlemutation in one of the so-called,“master genes” could lead to a bigchange in morphology.
7 REPTILES & AMPHIBIANS a. Water availability was not reliable. b. Air temperatures were variable, and air itself was not the strong supporting medium that water was, but it was a richer source of oxygen. Lungs had to be modified in ways that enhanced O2 uptake. Circulatory systems became more efficient in rapidlymoving oxygen to cells.
8 REPTILES & AMPHIBIANS Both of these modifications increase the capacity for aerobic respiration,thus generating more ATP for use inincreased activity.c. New habitats, including vast arrays ofplants, insects, necessitated keenersensory (vision, hearing, balance) input.As a result, different regions of the brainfurther developed.
9 REPTILES & AMPHIBIANS d. Fortunately, climate shifts in the Carboniferous provided an abundanceof insects as food for the amphibians.
10 REPTILES & AMPHIBIANSAmphibians developed with the characteristics of pharyngeal slits/gills, a dorsal nerve cord, a notochord, and a post-anal tail at different stages of their life. Though early tetrapods (which appeared 390 million years ago in the Devonian period) are often referred to as "amphibians", the first true amphibians appeared during the early Carboniferous period.
11 REPTILES & AMPHIBIANS Superorder Salientia Triadobatrachus (Triassic) Order Anura (frogs and toads) Jurassic to recent - 5,296 recent speciesOrder Caudata or Urodela (salamanders): Jurassic to recent recent speciesOrder Apoda (caecilians): Jurassic to recent recent species
12 REPTILES & AMPHIBIANS 2. Existing amphibians share several common characteristics:a. All have bony endoskeletons andusually four legs.b. Most shed their eggs into water,which is also home to a free-swimming larval stage.
13 REPTILES & AMPHIBIANS c. Depending on their habitat, amphibians can respire by use ofgills, lungs, skin, and pharyngeallining.d. The skin is usually thin and some-times supplied with glands thatproduce toxins. We’ll see thisshortly.
14 REPTILES & AMPHIBIANSThe word ‘amphibian’ comes from the Greek meaning, “both” (amphi), and bios, meaning, “life”.It describes cold-blooded animals with backbones that spend their lives both in fresh water and on land.
15 REPTILES & AMPHIBIANSWhen 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.
16 REPTILES & AMPHIBIANS The Class Amphibia contains three orders: Anura (frogs and toads)Urodela (salamanders and newts)Apoda (caecilians)
19 REPTILES & 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, mostadult amphibians breathe with a pair of lungs (salamanders are an exception)
20 REPTILES & AMPHIBIANS3. 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.
21 REPTILES & AMPHIBIANS5. Cutaneous respiration - besides breathing with their lungs, amphibians take up oxygen through their skin.
22 REPTILES & AMPHIBIANSDouble-loop circulation in amphibians:
23 REPTILES & AMPHIBIANSLife Cycle ‘Metamorphosis” of a Frog (pg )
24 REPTILES & AMPHIBIANS Frogs and Toads (4,000 species) 1. These animals are distinctive withtheir long hindlimbs capable of res-ponding to powerful muscles, whichallow them to leap into the air.2. Their success on land is due in partto: the excellent prey-graspingcapability of the tongue attached to thefront of the mouth.
25 REPTILES & AMPHIBIANS 3. Frog skin has mucous glands, poison glands & antibiotics that provideprotection against pathogens in anaquatic habitat.4. Scientists have noticed frog populationson the decline due to increases inparasitic attacks, predation, UVradiation, habitat losses & chemicalpollution.
26 REPTILES & AMPHIBIANS Frog versus Toad Frog has two bulging eyes strong, long, webbed hind feet that are adapted for leaping and swimmingsmooth or slimy skin (generally, frogs tend to like moister environments)Frogs tend to lay eggs in clusters.
27 REPTILES & 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 eyesThe chest cartilage of toads is different.Toads tend to lay eggs in long chains.
28 REPTILES & AMPHIBIANS Salamanders 1. Live in temperate zones & in tropicalareas of Central and South Americanumbering about 380 species2. When they walk, the body bends fromside to side, much like a fish movingthrough water.
29 REPTILES & AMPHIBIANS 3. Adults may retain larval features including gills and tail.4. Some larvae may become sexually maturebut not reach a true adult stage5. Both forms, larval & adult, are carnivorous.
30 REPTILES & AMPHIBIANS Caecilians 1. As amphibians evolved they lost their limbs & vision, but not their prey-capturing jaws.2. These unusual creatures live burrowedin the forest floor where they hunt forinvertebrate prey.3. Most of the 160 species burrow through the soil,using touch & smell to pursue insects & earthworms. The few aquatic types use electrical cues.
31 REPTILES & AMPHIBIANS Summary of amphibians: They are vertebrates they have bony endoskeletonThey have four legsTheir body plan and mode of reproduction is somewhere between “fishes” and “reptiles”
32 REPTILES & AMPHIBIANS - Their transition to land involved: development of legsmore efficient lungsmore efficient heart
33 REPTILES & AMPHIBIANS Because of this transition from water to land: Amphibians had to contend with a drier habitat. This required a modified way to enhance oxygen uptake through their lungsThis drier habitat required that they go back to a water environment for laying of eggs
34 REPTILES & AMPHIBIANSLegs, sufficient to support their body weight, allowed them to move from land to water when necessary.Their circulatory systems became more efficient to provide oxygen to all cells which, over time, increased the capacity for aerobic respiration and subsequently greater production of ATP – allowing for more activities.
35 REPTILES & AMPHIBIANS Scientific Classification of Reptiles Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Class: Sauropsida
36 REPTILES & AMPHIBIANS REPTILES Reptiles are tetrapods and amniotes, animals whose embryos are surrounded by an amniotic membrane. Today they are represented by four surviving orders:Crocodilia (crocodiles, caimans and alligators): 23 speciesRhynchocephalia (tuataras from New Zealand): 2 speciesSquamata (lizards, snakes and amphisbaenids ("worm-lizards")): approximately 7,600 speciesTestudines (turtles): approximately 300 species
37 REPTILES & AMPHIBIANSReptiles are found on every continent except for Antarctica, although their main distribution comprises the tropics and subtropics. Though all cellular metabolism produces some heat, modern species of reptiles do not generate enough to maintain a constant body temperature and are thus referred to as "cold-blooded" (ectothermic).
38 REPTILES & AMPHIBIANSSea Turtle for an exception: a reptile that elevates its body temperature well above that of its surroundings. Normally they rely on gathering and losing heat from the environment to regulate their internal temperature, e.g, by moving between sun and shade, or by preferential circulation — moving warmed blood into the body core, while pushing cool blood to the periphery
39 REPTILES & AMPHIBIANSReptiles evolved from tailed amphibian ancestors. There are nearly 8000 species that are divided into four orders; snakes and lizards, crocodiles and alligators, tortoises and turtles, and tuataras.A reptile has the following features;cold bloodeddry, scaly skintough shell on eggseggs are laid on land
40 REPTILES & AMPHIBIANS The Rise of Amniotes - Reptiles During the late Carboniferous, amphibiansgave rise to the amniotes (birds, reptiles, mammals).A. Four features were critical to amniotes’escape from water dependency:1. They produce amniote eggs with internalcovering membranes and a shell, which allowthe eggs to survive in dry habitats.
41 REPTILES & AMPHIBIANSAmniote egg contains a membraneous sac that surrounds and protects the embryo.
42 REPTILES & AMPHIBIANS Allantois The word comes from the Greek word for sausage, which the allantois resembles. This sac-like structure is primarily involved in respiration and excretion, and is webbed with blood vessels. It is primarily found in the blastocyst stage of early embryological development, and its purpose is to collect liquid waste from the embryo.
43 REPTILES & AMPHIBIANSThe structure first evolved in reptiles and birds as a reservoir for nitrogenous waste, but also as a means for oxygenation of the embryo. Oxygen is absorbed by the allantois through the egg shell . The allantois functions similarly in monotremes, which are egg-laying mammals.
44 REPTILES & AMPHIBIANSIn most marsupials, the allantois is avascular, having no blood vessels, but still serves the purpose of storing nitrogenous waste. Also, most marsupial allantoises do not fuse with the chorion.In placental mammals, the allantois is the precursor of the mature umbilical cord
45 REPTILES & AMPHIBIANS 2. First vertebrates to form eggs with internal membranes that conserveH2O and cushion an embryo, andmetabolically support it.3. Amniotes have a toughened, dry orscaly skin that is resistant to drying.
46 REPTILES & AMPHIBIANS 4. They have a copulatory organ that permits internal fertilization.5. Their kidneys are good at conservingwater.Again, these amniotes (mammals, turtles, lizards, snakes, crocodiles & birds) are the only tetrapods that can reproduce successfully away from aquatic habitats, while having the embryos develop to advanced stage before hatching or being born in a dry habitat.
47 REPTILES & AMPHIBIANS“Reptiles” demonstrate certain advantageous features compared to amphibians.1. Modification of limb bones, teeth, andjaw bones allowed greater exploitationof the insect life emerging in the LateCarboniferous.2. Development of the cerebral cortex permittedgreater integration of sensory input and motorresponse.
48 REPTILES & AMPHIBIANS 3. A four-chambered heart fully separated into two halves and more efficient lungsallowed greater activity. Crocodilianswere the first to exhibit this feature.Though the reptiles’ brain is smallcompared to it’s body mass, behaviorgoverned by it is advanced to that seenin Amphibians.4. Descendants of the surviving dinosaursbecame the lineage of reptiles.
49 REPTILES & AMPHIBIANS 5. Transdermal gas exchange seen in amphibians is abandoned byreptiles because of their well develop-ed lungs.
50 REPTILES & AMPHIBIANS Circulatory systems Fish Amphibian Reptile, Bird Mammal
51 REPTILES & AMPHIBIANSHumans, birds, and mammals have a 4-chambered heart that completely separates oxygen-rich and oxygen-depleted blood. Fish have a 2-chambered heart in which a single-loop circulatory pattern takes blood from the heart to the gills and then to the body. Amphibians have a 3-chambered heart with two atria and one ventricle.
52 REPTILES & AMPHIBIANSA loop from the heart goes to the pulmonary capillary beds, where gas exchange occurs. Blood then returns to the heart. Blood exiting the ventricle is diverted, some to the pulmonary circuit, some to systemic circuit. The disadvantage of the three-chambered heart is the mixing of oxygenated and deoxygenated blood. Reptiles, all birds and mammals, have a 4-chambered heart, with complete separation of both systemic and pulmonary circuits.
53 REPTILES & AMPHIBIANSA Sampling of Existing Reptiles – (Latin, to creep)Reptiles are a diverse group. They are considered an animal because they have basic amniote traits but not those of mammals or birds.A. Turtles1. The distinctive shell offers protection whileconserving water and body heat.
54 REPTILES & AMPHIBIANS2. The shell is connected to the skeleton Their teeth are tough, horny plates designed for gripping & chewingfood.3. Turtles lay their eggs on land, wherepredation is high.
58 REPTILES & AMPHIBIANS Lizards 1. Most lizards are small-bodied insect eaters; their most usual habitats are desertsand tropical forests.2. Lizards are also prey for many other animals,but are quick in movement and have theunique ability to sever their own tails if it isgrabbed by a predator.
61 REPTILES & AMPHIBIANS Snakes 1. Snakes are limbless but retain vestigesof hind limbs; they are excellentpredators.2. Snakes have the ability to swallow preylarger than they are due to flexible skulland jaw bones.3. All snakes are carnivores. Some suffocate theirprey, and some kill their prey with venom.
62 REPTILES & AMPHIBIANS95% of all living reptiles are composed of Lizards and Snakes.Kingdom:AnimaliaPhylum:ChordataClass:SauropsidaOrder:SquamataSuborder:Serpentes
63 REPTILES & AMPHIBIANS Tuataras 1. Although they resemble lizards, they are evolutionarily more ancient. Theyresemble amphibians with the brainand the way they walk.2. They do not engage in sex until theyare twenty years old!.
64 REPTILES & AMPHIBIANS 3. Only two species remain today; they live on islands off the shore ofNew Zealand.4. Like lizards, tuatarus have a 3rd eyeunder the skin with a retina, a lens,and nerves to the brain. They alsomay live to be 60 years old.
65 REPTILES & AMPHIBIANS Scientific Classification of Tuataras Kingdom: Animalia Phylum: Chordata Class: Sauropsida Order: Sphenodontia Family: Sphenodontidae Genus: Sphenodon
66 REPTILES & AMPHIBIANS Crocodilians 1. Crocodiles and alligators all live in ornear water.2. They are the largest living reptiles.3. The body plan includes a long snout;body temperature is regulated behavior-ally (ectothermic).
67 REPTILES & AMPHIBIANS 4. The ventricle of the heart is divided into right and left chambers – morelike the heart of birds than that ofother reptiles.
68 REPTILES & AMPHIBIANS4. Like other reptiles and birds, crocodilians adjust body temperature with behavioral and physiological mechanisms.5. They are like birds in displaying complex social behaviors, such as parents guarding nestsand assisting hatchlings into water. This traitand others suggest that crocodilians and birdsshare a common ancestor.