tetrapods - reptiles

Question 1

outline some basic characteristics of reptiles

Answer 1

1) lay hard-shelled eggs
2) bodies covered in scales
3) clawed toes
4) lack feathers or hair
5) respire solely with lungs

Question 2

what did the evolution of the amniotic egg allow

Answer 2

• to lay their eggs in terrestrial locations
• air-breathing juviniles hatch
• competitive advantage over restricted amphibians

Question 3

outline what the different components of the amniotic egg allows

Answer 3

1) amnion - cushions embryo
2) yolk sac- contains food
3) allantois - stores waste, gas exchange
4) chorion - allows oxygen and co2 through the shell

Question 4

how do reptiles reproduce

Answer 4

• fertilisation is internal
• many reptiles are oviparous (hatch after layed) but some are vivparous
• most do not care for their young

Question 5

outline some of the characteristics of scales

Answer 5

• tough, dry, waterproof scaly skin
• develops as surface cells fill with keratin
• protects against desiccation and injury
• thin epidermis is shed periodically

Question 6

outline how respiration and circularisation occurs in reptiles

Answer 6

• based on an aspiration pump
  1) pump acts on walls of lung to change its shape and induce air flow
  2) intercostal muscles move ribs, altering shape of body walls around lungs
  3) inhaltion - ribs move out increasing cavity around lungs decreasing air pressure
  4) exhalation - ribs move in compressing lungs expelling air

Question 7

outline how locomotion is achieved in reptiles

Answer 7

• need to maintain center of gravity above its base of support
• most have a broad quadrangular base
• when one leg is lifted it changes to a triangle
• therefore lizards and crocidilians bend their vertebral column

Question 8

what is meant by ‘carriers constraint’ as a result of locomotion

Answer 8

the sideways flexing expands one lung and compresses the other therefore shunting air from lung to lung
this means most lizards have restricted to short bursts of activity

Question 9

how have reptiles adapted to over come carrier constraint

Answer 9

• monitor lizards use positive pressure gular pumping to assist lung ventilation
• snakes have asymmetrical lungs with the left ling being reduces

Question 10

what is bipedalism

Answer 10

the parasagittal stance evolved in both mammals and dinosaurs/birds where only two legs are used for locomotion

Question 11

how have amphibian and reptile jaws evolved differently

Answer 11

amphibians - quick closure but little force
reptiles - crushing pray
therefore jaw muscles need to be larger and longer

Question 12

what is meant by a kinetic skull

Answer 12

term for significant movement of skull bones relative to each other in addition to movement at the joint between the upper and lower jaw
- mobility of skull can increase bite force

Question 13

what are the remaining 4 orders out of 16 of reptiles

Answer 13

1) crocodilia
2) squamata (lizards and snakes)
3) rhymnchocephalia
4) chelonia/ testudines