Amphibians 1 Flashcards
What are the 3 main lineages of amphibians?
- Frogs & toads - anura
- Salamanders - urodeles
- Caecilians (snakes) - gymnophionans.
Describe the stages of amphibian metamorphosis.
- Pre-metamorphosis: tadpole size increases.
- Pro-metamorphosis: hind legs appear, growth slows.
- Meta-morphic climax: forelegs emerge and tail regresses.
What triggers and controls metamorphosis?
Controlled by hormones and associated receptors in response to environmental cues. Thyroid hormones are involved.
(Gundersnatch fed tadpoles thyroid hormones and they began to metamorphose)
What are the shared derived characteristics of modern amphibians?
- Smooth moist skin
- Multiple respiration methods
- Pedicellate teeth
- Green rods
- Operculum - Columella complex (hearing)
- Levator bulbi muscle.
Describe amphibian skin features.
- Absence of bony/ keratinised scales
- Absence of keratinised true claws
- Mucus glands
- Poison glands.
Describe the multiple respiration methods in amphibians.
- Cutaneous - gas exchange occurs across moist skin
- Buccopharyngeal - gas exchange occurs in buccal cavity/ pharynx
- Pulmonary - gas exchange occurs in paired lungs
- Gills - larval forms and neotenics (neoteny - adults that retain juvenile characteristics).
Describe blood circulation in amphibians.
- 3 chambers
- Right atrium - deoxygenated blood
- Left atrium - oxygenated blood from the lungs and skin
- Both atria empty into single ventricle
- Left atrium blood sent to head via carotid arteries
- Right atrium blood sent to skin and lungs to pick up more oxygen via pulmocutaneous arteries
- Blood in aortic arches has been mixed and supplies rest of body.
In what period did amphibians arise?
Devonian.
What is the main environmental cue for metamorphosis?
Day length. 🌤
Describe amphibian skeleton structure.
- Skulls are flattened, relatively small and have fewer bones than water-dwelling animals
- Vertebral column lost much flexibility to transmit force from limbs to body
- Have pelvic girdle which attach pelvic appendages to vertebral column to provide support on land.
What are Pedicellate teeth?
Crown and base separated by uncalcified dentine/fibrous tissue. May allow for flex of tooth for handling prey.
What are green rods?
- Present in frogs and salamanders
* Distinct type of retinal cell (photoreceptors).
What is a levator bulbi muscle?
- Muscle found beneath eye
- Bulges eye forward and increases buccal activity
- Used in breathing and swallowing.
