Amphibians & Reptiles Objectives : 1) Distinguish between ectotherms & endotherms; and between amphibians & reptiles and the various groups of each 2) Describe states of torpor 3) Explain amphibian metamorphosis 4) Compare and contrast amphibian & reptile anatomy and physiology
1) Distinguish between ectotherms & endotherms; and between amphibians & reptiles and the various groups of each
2) Describe states of torpor
3) Explain amphibian metamorphosis
4) Compare and contrast amphibian & reptile anatomy and physiology
Vertebrata * amphibia * ectotherm * endotherm * torpor *
hibernation * estivation * metamorphosis * nictitating membrane * maxillary
teeth * vomerine teeth * tympanic membranes * eustachian tube * alimentary
canal * pyloric sphincter * duodenum * ileum * mesentary * cloaca * liver *
gallbladder * pancreas * atrium * ventricle * pulmonary respiration *
cutaneous respiration * mouth (buccal) respiration * urostyle * axial skeleton *
appendicular skeleton * pectoral girdle * pelvic girdle * femur * tibio-fibula *
metatarsals * phlanges * cloaca * thyroxine * amniote egg * allantois *
chorion * amnion * yolk sac * parietal eye * carapace * plastron *
Jacobsen’s organ * scutes * molt
Class Amphibia (2 lives)
- probably evolved from lobe-finned fish that had primitive lung
- appeared about 345 million years ago
- ectotherms (cold-blooded) they cannot make much of their own body heat (poor temperature regulation) so certain adaptations are necessary
torpor – dormant state that aids in survival during cold/hot periods, drought, etc.
2 Types of Torpor:
1) hibernation – winter dormancy
2) estivation – summer dormancy
- usually aquatic larva (with gills) undergo metamorphosis (change) into terrestrial adults (with lungs)
- skin is usually thin, moist, & covered with mucus, noscales
- nostrils are connected to the mouth cavity
- respiration involves gills or lungs, skin (cutaneous), and mouth (buccal) cavity Why must skin stay moist?
What substance is needed to keep skin moist?
Could their nostrils be used for respiration?
- usually have external fertilization
- eggs require moist/wet environment. They have no shell and no inner membrane
- larval form has a 2-chambered heart (1 atrium receives blood and 1 ventricle pumps blood to body) Adult has 3-chambered heart (2 atria and 1 ventricle) - oxygenated blood mixes with deoxygenated blood
1) Tachystoma (“rough mouth”) Ex: mud eels
- small forelimbs
- no hind limbs
2) Apoda (“without legs”) Ex: caecilians
- burrowing, worm-like organisms
- blind or poor eyesight, they use tentacles near mouth to sense prey
How might their eyesight be related to their habitat?
- eat worms & other invertebrates
- internal fertilization
- young are born live, NO EGGS laid
Which of the following terms might apply?
Oviparous, ovoviviparous, viviparous
3) Urodela (“visible tail”)
- long tails
- smooth, moist skin
Ex: salamanders & newts (a mostly aquatic type of salamander)
- internal fertilization (male leaves package of sperm for female to pick up)
- freshwater salamanders keep their gills even as adults
- Mudpuppy remains in larval form but can reproduce
4) Anura (“without a tail”)
Ex: toads & frogs
Toads (vs. frogs)
- drier, bumpy skin
- shorter legs than frogs
- stockier bodies
- tolerate drier environments
- Both frogs and toads: lay eggs in water or foam to keep them moist, eggs hatch into tadpoles
- smooth, moist skin (might be mucusy)
- most live in or very near water
- fairly long hind legs
- Larval form is usually a tadpole (Figi has an exception)
- eggs are fertilized externally
Frogs and toads may burrow into ground to hibernate. Toads living in hot. Dry areas sometimes burrow into ground to estivate.
Most frogs & toads eat insects or worms. Tadpoles usually eat aquatic plants.
Egg tadpole with tail, no legs hind legs begin growing front legs slowly appear & tail slowly disappears
- eyes bulge above head. This allows vision above water
- eyelids can blink
- a nictitating membrane (3rd eyelid) attached to loer eyelid keeps the eye moist & protects the eye under water
- 2 nostrils also on top of head (can be used for breathing)
- sticky tongue (catches bugs)
- eyes push down on roof of mouth to aid in swallowing
- maxillary teeth (if present) line the edge of the upper jaw
-vomerine teeth (2) project from roof of mouth just behind the nostril openings in the mouth
Tympanic membrane, “eardrums,” are just behind the eyes. They work in air or water
Eustachian tube connects “ears” to mouth cavity (helps equalize pressure)
Alimentary canal includes: esophagus, stomach, small & large intestine, cloaca
pyloric sphincter – at bottom of stomach, keeps food moving into small intestine & not back up into the stomach
duodenum – 1st part of small intestine
ileum – middle part of sm. Intestine
(jejunum is the last part of sm. Intestine)
Mesentery – tough, thin tissue that holds the intestines in place
Cloaca – digestive wastes, eggs/sperm, & liquid wastes (from kidneys) all pass through this area before leaving the body
The alimentary canal includes only the organs that food/food wastes actually pass through. However, the digestive system also includes:
Liver – produces bile (breaks down fats)
Gallbladder – stores bile
Pancreas – secretes digestive enzymes into small intestine
Adult’s 3 chambered heart allows some mixing of oxygenated blood with deoxygenated blood.
This is more efficient than 2 chambered hearts.
Right atrium receives blood from body (deoxygenated)
Left atrium receives blood from lungs (oxygenated)
Ventricle pumps blood to body & lungs
Larva (tadpoles) breathe through gills
Pulmonary respiration – breathe through lungs
Cutaneous respiration – breathe through skin in both air and water, especially important during torpor
Mouth (buccal) respiration – oxygen diffuses across mouth lining
Kidneys – filter nitrogenous wastes from blood, making urine
skin allows carbon dioxide to escape along with nitrogenous wastes
Axial skeleton: skull and 9 vertebrae (backbones) followed by an usostyle – a long slim bone extending to pelvic girdle
Pectoral girdle – “shoulder” bones, where front legs attach. Frogs have nofull ribs so this is all that protects organs.
Pelvic girdle – “hip” bones, where hind legs
Legs: (must know)
Femur – upper leg bone
Tibio-fibula = lower leg bone
Tarsals – “ankle” bones
Metatarsals – foot bones
Phalanges – toe bones
Male: 2 testes near kidneys. Sperm leaves body through cloacal opening. Fertilization is external.
During breeding season the male’s forelegs and first “fingers” may swell – used to hold female.
Males also have vocal sacs in the mouth, on the lower side, toward the back. (These amplify their calls louder than female calls)
Females: 2 ovaries near kidneys. Eggs pass from ovaries, down oviducts (where they receive jelly-like coating), and out cloacal opening.
Eggs usually hatch about 12 days after fertilization. Tadpoles change into frogs due to a hormone called thyroxine.
- ectotherms (behavior helps regulate temperature)
- * skin covered with scales made of keratin
- * dry, thick skin
- * internal fertilization (doesn’t require moisture for sperm to swim to skin)
- 2 pair of legs, except for snakes
- toes have claws (aid movement on land)
- * lungs for respiration (during all stages of development) – protected by rib cage
- 3-chambered heart with partially divided ventricle or 4-chambered heart (in some alligators/crocodiles) This increases the amount of oxygen carried to body cells.
- * nitrogen wastes excreted as uric acid in a semisolid paste (conserves water)
- *amniote egg
* These allowed full life on land, unlike amphibians
Shell is leathery to hard (calcium carbonate) and porous (allows gas exchange)
Chorion lines the inside of the shell and encloses the rest of the egg
Amnion surrounds embryo & the salty fluid it floats in
Allantois stores nitrogenous wastes until hatch time
Yolk Sac holds food source for developing reptile
Albumin is a food source for protein
1) Tuataras – only surviving species in its order, has a 3rd eye on top of its head (parietal eye) – NOT used for sight but for measuring light. They are also unusual in that they are more active in the cold.
2) Turtles & tortoises
(Tortoises are usually land “turtles”)
Protected by a leathery or hard shell. The upper shell is fused to the vertebrae and is called a carapace. It’s composed of mpdified scales called scutes.
The lower shell is called the plastron.
3) Crocodiles, Alligators, & Caimans:
- live in or near water
- have a 4-chambered heart usually
- have different head shapes which helps distinguish
them from one another
4) Lizards & Snakes:
- “hinged” lower jaw is not directly attached to the skull
- some can regenerate tails (lizards like the iguana, but only ONCE)
- snakes have more vertebrae & ribs than any other animal
- Jacobson’s organ in a snakes mouth detects odors collected by darting the tongue in and out
- snake skin does not grow so it must shed its skin to grow (molt) Lizards also molt.
- skin of lizards & snakes is covered with scales. Larger row of scales on snake’s ventral side gives traction for movement (scutes)
Poisonous US snakes include: coral snakes, rattlesnakes, cottonmouth, copperhead
Examples of lizards: gecko, anole, Gila monster (poisonous), Komodo dragon
All are either oviparous or ovoviviparous (with internal fertilization)