Lecture 9 RH - Reptiles Flashcards
What kind of grouping are amniotes?
Monophyletic group within tetrapods.
What lifestyle do amniotes have?
A terrestrial lifestyle; some colonised air and some returned to water
What type of fertlization do amniotes have?
Internal fertilization
What kinds of animals are the amniotes?
Reptiles/Birds
Mammals
What are the general features of amniotes?
Thicker and more waterprood skin
Rib-ventilation of the lungs
Stronger Jaws
High-pressure cardiovascular system
Water-conserving nitrogen excretion
Expanded brain and sensory organs
Amniotic egg
What are the layers of membranes surronding the amniotic egg?
Yolk sac: Contains nutrients
Chorion: Allows gas exchange with environment
Amnion: Surrounds and cushions embryo with the help of fluid
Allantois: Stores wastes and allows gas exchange
Why is the shell of an egg porous?
Shell contains pores so that the embryo could breath
What does the layer between the egg’s shell and the chorion contain?
Albumin
In what order does everything happen with egg production?
fertilization -> membranes around embryo -> shell
What are the general features of reptiles?
Tetrapods with 5 digits per limb
Internal fertilization
Amniotic with calcareious or leathery shelled egg
No aquatic larval stage
Respiration by lungs
Cloaca
Ectothermic and poikilothermic (birds are homeothermic and enothermic)
Epidermal keratin forms scales (this forms feathers in birds and hair in mammals)
Skull with one occipital condyle
How many occipital condyles do reptile skulls have?
1; compared to 2 in mammals
Are reptile and fish scales homologous?
No, reptilian scales are epidermal whereas fish scales are mesodermally derived (from the dermis of the skin)
What is the function of reptile scales?
Physical protection and prevention of dessication
Some reptiles have bony dermal plates with added strength
What do reptile hearts look like?
All reptiles have a septum between left and right atria.
Most reptiles have a partial septum dividing the ventricle into 2 chambers.
Crocodilians have a complete septum between left and right ventricles.
What are the developments in locomotion seen in reptiles?
Improved body structure and support and limbs.
Ancestral form of locomotion is by lateral undulations of trunk which compresses lungs alternatingly in order to run.
Improvements include bipedal locomotion, movements of ribs, pelvis, organs, and limb movement independent of trunk bending.
What are the developments that reptiles have in order to respire more efficiently?
Larger and more efficient lungs
Lungs are inflated by negative pressure by enlarging body cavity (without using a diaphragm)
Turtles move their visceral organs around in order to create the negative pressure.
Lizards ventilate the lungs by compressing and expanding the rib cage
Crocodiles inhale by expanding the rib cage and pulling the liver back and rotating pubic bones.
What developments in the reptiles have allowed more efficient metabolism to take place?
More effient circulatory system with 4 chambered hearts.
What are the advantages and disadvantage of ectothermy?
Advantages:
Efficient conversion of food into biomass
Can thrive in ecosystems of low productivity
Can survive with low metabolic rate
Disadvantages:
External temperature limits activity
Requires behavioural adaptations for finding thermal microenvironments
Becoming inactive for part of the year
Limitations on latitudinal range
How long ago did amniotes arise from amphibians?
300 mya
What are the 3 groups of amniotes?
Anapsids: No temporal bone holes posterior to orbits. (earliest reptiles)
Synapsids: One pair of temporal holes posterior to orbits for attachment of jaw muscles. (gave rise to therapsid reptiles and mammals.
Diapsids: 2 pairs of temporal holes posterior to orbits for attachments of jaw muscles. They gave rise to all other reptiles including dinosaurs and birds. Turtles secondarily lost these openings
What basis is there for amniote division?
Skull structure