The diapsids

Question 1

Chelonia morphology

Answer 1

Turtles - fossils 220mya
•staggered bits at back of skull suggest holes covered
•no teeth - lost, have horny beak for rasping at food
•can bend neck into their shell
•2 different groups bend it in an S shape or to the side

Question 2

Chelonia skeleton modifications

Answer 2

•covered by carapace (on top) and plastron (bottom)
-restrictive but provides protection
•carapace has keratinised scoots on top making pattern
-made of bone underneath, extensions of the ribs
•vertebral column and ribs fused to carapace
•plastron has some bone, also covered in keratin on outside

Question 3

Chelonia respiration

Answer 3

Has to be different due to carapace fused with ribs and vertebrae
•lungs at top of body/shell
•fused to viscera beneath membrane
•muscles below viscera
•animal breathes due to changes in viscera
•muscles contract and push on viscera - upwards, lungs become smaller and exhales - vice versa for inhaling
-linked to legs too
•aquatic breathe through cloaca which is vascularised, some using mouths

Question 4

Sexes in Chelonia

Answer 4

Environmental sex determination using temperature
•reach certain temp suddenly all F - 30+°C, below = M
•lizards get F at lower, and M at higher temps
•usually sex that is bigger at higher temps

Question 5

Lepidosaurs

Answer 5

1. Sphenodonta - tuatara

2. Squamates - lizards and snakes

Question 6

Sphenodonta

Answer 6

Tuatara
•found in NZ - extinct on mainland, but found in surroundings
•diapsid skull
•nocturnal - associated with burrows of seabirds, live alongside seabirds in their burrows
•mainly feed on inverts, but sometimes chicks
•nocturnal has low body temp but still active
•can raise this in day when sunny

Question 7

Squamates

Answer 7

• modified diapsid skull
• snakes lost both bars, lizard only one (bottom bar)
• 95% of all living reptiles

Question 8

Lizards

Answer 8

•large range in size
•smaller are insectivorous (associated with humans as attracted to light)
•larger are herbivores as can’t feed on insects
-some carnivores, Komodo dragon and Tegu
•limb reduction - evolved over 60 times independently
-burrowing and living in vegetation
•surface dweller limbless lizards - have longer tails, can control movements better
-burrowing limbless lizards - shorter tails as long gets in way, cannot burrow effectively

Question 9

Snakes evolution

Answer 9

•essentially specialised limbless lizards
•evolved from lizards that were burrowing - then became surface dwellers - losing limbs and becoming blind
•snakes have different eyes form lizards - went blind in burrowing or developed differently and came back to surface with different eyes
-theory came from marine E but burrowing is better

Question 10

Snake morphology

Answer 10

• very long thorax and short tail (varies) and neck
• Oct4 manipulated gene leads to increase in thorax length and causes reduction of limb development (seen in mice)
• most lack pelvic and pectoral girdles - but some are vestigial
• long body - concentrates weight to be distributed into tube, reducing diabetes as a consequence

Question 11

Snake eating and adaptations for this

Answer 11

• jaw is extremely flexible, can take in food bigger than diameter
• 5 points of articulation in jaw, where it can move apart
• do not dislocate jaw, just flexible
• backward pointing teeth to help push food back into stomachs

Question 12

Snake predation methods

Answer 12

•some snakes swallow prey whole alive
•some subdue prey by…
-fangs injecting venom to kill or subdue
-constrictors will wrap around prey restricting blood flow to vital organs causing death that way, requires strong body muscles

Question 13

Crocodylia

Answer 13

Alligators, gharials and crocodiles
•close relationship to birds
•diapsid with some features like mammals
•sensory structures in mouth, little bulges are very sensitive to movement and touch
•jaws used for different purposes
•moves in different ways - crawls with legs down, lift legs up and walk on back, and gallop

Question 14

Diapsid skull and head adaptations

Answer 14

• teeth imbedded in skull - thecodont teeth (convergent evolution with mammals)
• secondary palette which allows them to breathe whilst underwater

Question 15

Jaws used for…

Answer 15

• manipulate food - forelimbs are too small
• needs to be sensitive to find prey
• use it for parental care - carry young in mouth and open up the egg when offspring hatching

Question 16

Crocodilian behaviour

Answer 16

• communicate whilst mating and territorial
• young communicate with stress calls for adults to help
• show behaviour similar to birds (parental care) and mammals (play)
• young cared for in large groups - sophisticated
• wait for prey to decompose (easier to manipulate) and wrap in vegetation to pull bits off