Amphibians Flashcards
What is the crown group that include modern aphibians
Tetrapods, which split into amphibians and amniotes
What are the defining features of modern amphibians
- Permeable skin, essential for gas exchange and water/salt regulation
- Vascularised skin
- Mucus-covered, smooth skin with dermal glands
- Skin involved in signaling and salt uptake
- Diverse body forms, reproductive strategies, and habitats
- Never returned to marine environments
What are the three orders of modern amphibains
- Urodela (salamanders and newts)
- Anura (frogs and toads)
- Caecilia (caecilians)
All are monophyletic but have very different body forms
Describe the generalised developmental cycle of amphibians
- Aquatic egg-laying, external fertilisation
- **Tadpole **phase: feeds on algae → insects
- Develops gills, then** hind legs and lungs**, then forelegs
- Tail regresses → froglet becomes terrestrial
What makes amphibian skin unique
- Thin, permeable epidermis with dermal glands
- Produces toxins (e.g., batrachotoxin, bufotoxin)
- Chromatophores for camouflage and warning colouration
- Key role in respiration, especially in low temperatures
How do amphibians exchange gases
Via lungs, skin, and sometimes gills (external in larvae)
In cold conditions, skin dominates O₂ uptake
At higher temps, lungs for O₂, skin still used for CO₂
Some salamanders (e.g. Plethodontids) lack both lungs and gills
What visual adaptations do amphibians have for air and water
Rigid spherical lens with high refractive index
Lens is pulled forward to accommodate near objects
Nictitating membrane protects cornea
Green rods in retina: motion-sensitive
Binocular vision for distance judging
Describe the habitat and reproduction of urodeles
Mostly aquatic during breeding, some permanently aquatic
Internal fertilisation
Lay eggs singly, often attached to vegetation
Larvae have** external gills**, metamorphose into terrestrial forms
What are some unique urodeles and their adaptations?
Ambystoma: paedomorphic axolotl.
Megalobatrachus / Andrias: large cold-water salamanders.
Proteus / Typhlomolge: blind cave species with external gills.
Amphiuma / Siren: aquatic, reduced or no limbs, retain larval features.
What are key skeletal traits of urodeles?
- Weak skull, large orbits.
- Short ribs, no rib cage.
- Long tail with myotomes.
- One sacral vertebra.
- Short limbs, 4 fingers, 5 toes.
- Undulating swimming, sprawling gait walking.
How do urodeles swim and walk?
Swimming: lateral body undulation, tail propulsion.
Walking: complex limb movement, body bending, swinging gait.
What features define anurans?
Lack tails.
Specialised for** jumping and walking**.
Found on all continents except Antarctica.
Range from 10 mm to 30+ cm (e.g., Goliath frog).
What are skeletal features of anurans?
Short spine, no tail.
Long hind limbs with fused tibiofibula.
Shock-absorbing pectoral girdle.
Adapted for powerful jumping.
Describe the mechanics of anuran jumping.
Uses 4 joints:
1. Sacro-iliac
2. Ilio-femoral.
3. Femoro-tibial.
4. Tibio-tarsal.
Arms absorb landing.
Hind legs re-flexed after landing.
How do anurans communicate acoustically?
Vocal sacs amplify calls.
Larynx controls airflow.
Species-specific sounds.
Used for mating, territory, and alarm.
What’s typical of anuran reproduction?
External fertilisation.
Many lay eggs in water, with a tadpole stage.
Some have post-oviposition parental care.
What are climbing adaptations in frogs?
Adhesive toe pads.
Curved digits for gripping.
Highly agile arboreal locomotion.
What are the main features of caecilians?
Legless, burrowing amphibians.
Segmented skin for grip.
Small, covered eyes, no ears.
Right lung elongated.
Retractable chemosensory tentacles.
Skull adapted for burrowing.
Describe caecilian skeletal features.
Penetrating skull.
Large nasal openings.
Sharp pedicellate teeth.
Small orbits, reduced ears.
Long rib-bearing trunk, short tail.
How do caecilians reproduce?
Internal fertilisation via male cloacal organ.
Direct development, no larval stage.
Some species are viviparous.
Why are caecilians evolutionarily interesting?
Convergent with snakes and legless lizards.
Traits:
No limbs or girdles.
Burrowing skull.
Concertina locomotion.
Single long right lung.
Vestigial eyes, light detection only.
Specialised tentacles.
