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| Question | Answer |
| Aspects of Amphibian Skin | Mucous glands Granular glands (poisonous alkaloid compounds) Thin skin (gas transfer) More terrestrial = more keratin (prevent desiccation) |
| Why would the loss of an aquatic growth phase in amphibians be effective? | Spend less energy transitioning from aquatic lifestyle to dry land; encounter fewer water predators. |
| Describe unique teeth of amphibians | Pedicellate teeth (unique to amphibians and some temnospondyls) Have uncalcified suture dividing the pedicel from the calcified tip |
| Describe Anurans | Order Anura Paired limbs, no tail, jump, tympanum present to transmit sound to the inner ear, external fertilization |
| Describe the amphibian skull | Flattened and open with big jaws Palate is highly reduced (allows eyeballs to drop into mouth when swallowing) Hyomandibula becomes stapes- effects sound transmission |
| Differences of anuran axial skeleton from that of amphibious fish | Shortened vertebral column Atlas (cervical vertebrae) allows movable joint through two condyles Formation of urostyle between elongated pelvic girdle bones |
| Specializations of anuran appendicular skeleton | Fused radius/ulna to absorb landing shock Tibia/fibula bones also fused for sturdiness Longer hind limbs |
| Features of salamanders | Order Caudata Paired limbs and long tail Suction feed in water and projectile tongue on land No tympanum external or internal fertilization by means of spermatophore transfer |
| Salamander skeleton | Long back (10-60 pre-sacral vertebrae) Flattened open skull Poor ossification w common reduction and loss of bones |
| How salamanders move | Dual locomotion short walking limbs and swimming tail both modes of locomotion are distinct and controlled by different sets of neurons in brainstem |
| Caecilians | Order Gymnophiona No limbs or girdles solid and compact skull for burrowing Tropical habitats Internal fertilization 60-285 trunk vertebrae w a short or absent tail |
| Describe what we know of the origin of modern amphibians | Fossil gap between modern groups and early tetrapods Originated from Jurassic period (~200 Mya) Hypothesized to have developed from temnospondyls, lepidospondyls or both |
| What is paedomorphosis and why can it mislead us? | when larval characteristics of ancestors appear in adults of descendants We may conclude that two unrelated species are closely related because they share the same loss of bones and ossification |
| Describe early amniotes | evolved in the early/mid-Carboniferous (360-330 Mya) Small w a slight but highly ossified skeleton ("lizard-like") Jaws, teeth and neck modified for improved predation |
| What are the major groups of amniotes? | Synapsids: Mammals Sauropsids: reptiles and birds Diapsids: Lepidosaurs (lizards and snakes); Archosaurs (dinosaurs, birds and crocs) We don't know where turtles fit! |
| What's so special about the cleidoic egg? | Semi-permeable shell that allows gas exchange Extra embryonic membranes Amnion: surrounds w water Chorion: surrounds the embryo and yolk sac Allantois: fills w waste Allows development entirely on land & no complex metamorphosis More energy invested in each egg |
| Other derived characteristics of amniotes | Low skin permeability - prevent desiccation Lung ventilation aided by ribs Increased body support due to increased apparent weight out of water |
| Amniote axial skeleton | expanded regionalization of the vertebral column lumbar limbs lost in some amniotes to expand hindlimb forward movement -> rapid locomotion |
| Atlas and axis vertebrae | Skull-atlas joint (vertical nodding and horizontal tilting of head) Atlanto-axial joint (twisting movement) Maintains bony strength of neck and allowing cranial mobility |
| Body support of vertebral column | Body suspended between legs w vertebral column as the 'bridge' between support posts Makes use of arch designs (trunk vertebrae is held in arch by abdominal muscles and sternum) Cervical vertebrae held in arch by neck ligaments |
| The role of the hip bone in body support | balances heavy parts against each other (acts as a fulcrum) requires a firm vertebral column vertebrae are tied together by strong ligaments between neural spines |
| Changes in skull openings | openings evolved to reduce skull weight and provide room for jaw muscles # of openings varies in amniotes Anapsids: no fenestrae Synapsid: one lower temporal fenestra (mammals) Diapsid: two temporal fenestrae (reptiles, birds, dinosaurs) |
| Describe turtles and their diversity |
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