Amphibians Flashcards
Limbs
Ankle/wrist joints
Pectoral girdle
Pectoral girdle free from skull
Discrete shaft of humerus
Tiktaalik
intermediate between fish + tetrapods
Scales - fins - gills - lungs - fish
Eyes on top of skull - neck - ribs - fin skeleton - flat skull - tetrapod
Amphibians
Frogs salamanders, frogs and caecillians
Amniotes
Mammals, birds and reptiles
Water to Land
Body support - need limbs
Gravity is a larger factor
Limbs larger - more differentiated
Limbs have bones and joints - more robust
Locomotion
Pectoral girdle - disassociated from head skeleton to avoid pressure on skull
Limb girdle - more closely attached to axial skeleton - vertebral column
Terrestrial is harder on joints
Fin based undulation -> pushing off substrate
Extrinsic to intrinsic musculature
Body shape
decrease in hydrodynamics
return to elongate in secondary aquatic forms
Respiration
Gills -> gills + lungs -> lungs
Decreased reliance on culeneous respiration - still used by amphibians
Ventilation increases in later tetrapods - powered by rib cage muscles
water balance
Amphibians live in moist environment - terrestrial
Excretion of conc urea conserves water
mucous gland limit evaporation
Behave adaptions limit water loss
Sensory systems
Sound travel diff in air
Evolution of bony structure that better conducts vibrations in inner ear
Lat lines disappear in most - some frogs
Feeding
Suction feeding not possible
Jaws + tongues
Elaboration of tongue - enhanced prey capture
Caecilians
Apoda
Elongate - no limbs - no limb girdles
Small eyes - some covered by skin
Body segmented by annular grooves - some have scales
Specialised for burrowing - ossified compact skulls
Some evolved fins - aquatic
Left lung - rudimentary
Moist forest soil/freshwater
Mainly oviparous with aquatic eggs + larvae (some terrestrial)
Some viviparous - scraping teeth for placental lining
No ear opening
Carnivores
Newts + salamanders
Urodela
Have a tail
Some entirely aquatic (some terrestrial)
Limbs equal length
Walk side to side - bending body
Oviporous
larval stage skipped in some
Internal fertilisation in most (some external)
Males produce spermatophores - females pick up with cloaca sperm storage - eggs fertilised as they are passed through
Paedomorphs - retention of larval features after maturity -axolotl - gills retained - entire life in water
Frogs
Anura
No tail
Legs always present in adults
Adapted for locomotion - hind legs larger than fore legs - webbed toes
Visual + vocal comms for breeding
Large vocal sacs amplify calls
External fertilisation
Most oviparous - aquatic eggs + larvae
Thermal regulation
Ectotherm - body temp matches environment
Behavioural thermal regulation
Basking - water loss through evaporation
V permeable vascularised skin
Some only bask in water
Overheat through evaporative cooling
Water economy
70-80% of body mass - adults don’t drink
Exchanged through skin + lungs - cutaneous respiration
Delicate skin - mucus glands
Aquatic excrete dilute urine
Terrestrial - urea + uric acid - more concentrated
Urinary bladder - water store
Prey detection and capture
Larvae don’t compete with adults
Tadpoles - herbivores/opportunistic omnivores
Adults - carnivores
Vision is primary prey detection
Lungless salamander - powerful tongue
Defence against predators
Eggs - arthropods + leeches
Larvae - arthropods/fish/turtles/birds
Adults - Birds/snakes/spiders/crabs/fish/turtles/amphibians/mammas/bats
Concealing colours + shapes
Disruptive colours - mid dorsal line - breaks up outline
Confusing colours
Enlarging body - pretend to be something bigger - eye spots on back
Aposematic colours
Parental care
Aquatic eggs - larvae - small adults
Terrestrial eggs - small adults
Caecilians - at least two brooding adults provide additional food for young
Xenopus
Lakes/swamps/ditches/dams
Arthropod/fish diet
Tadpoles - filter feeders
Bird/fish - pred
Tolerance to extreme conditions - aquatic
Can aestivate over 6 months in mud of dried pond
Excrete toxic ammonia - switches to urea - accumulates in tissues - excreted when water returns
Go without food for 1 year
Metabolism slows to conserve energy
Sensory perception - olfaction adapted for air + water
eyes adapted for vision in air
Sound perception for in water - retained lateral line
Distasteful - lethal toxins + antibacterial secretions
Spadefoot toad
Dry habitats - deserts
Hibernate underground at depth of 1m
Breed when rain falls
Eggs laid in pools
Can survive 2 years without rain
Nitrogenous excretion - stored as urea during hibernation
Can lose 40% body water
Canabalistic tadpoles - crowded pools
