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
Are turtles considered anapsids, synapsids, or diapsids?
Anapsids (secondarily)
Interesting fact:
Crocodilians are more closely related to birds than to other reptiles
What are the 3 main clades of reptilians?
Turtles
Snakes, lizards, tuataras
Crocodiles, birds, dinosaurs
What order are tortoises/turtles?
Testudines
Where does the shell attach to the turtle body?
Shell is fused to the ribs and vertebrae of the thorax
How is the lung ventillated in turtles?
Muscular contractions of the thorax, abdomen, and limbs.
Viscera are moved in a way where pressure is created to open the lungs for ventillation
What are tortoises referring to?
Terrestrial turtles
Fact
Turtles are endangered
What is the turtle’s life cycle?
Egg buried in the sand
Sand travels to the water and hatchlings must travel to the water
What determines the sex of a turtle?
Nesting temperature of the egg
How are turtles guided between feeding and nesting grounds?
Scents
Currents
Lights
Magnetic field
What order are snakes and lizards a part of?
Squamata
Which reptiles are the most recently evolved?
Squamata
Why can snakes open their mouth so wide?
They have a kinetic skull with movable quadrate bone which allows large mouth opening.
Very strong jaw muscles
Are squamates viviparous?
Some are by retaining egg in oviduct until it hatches
What suborder of squamata are lizards?
Suborder sauria
Which are more primitive, lizards or snakes?
Lizards
How are sauria eyes different to snakes?
Lizards have movable eyes and very good vision
Where are saurians typically found?
low productivity environments such as dry forests, deserts, or grasslands
What are worm lizards?
No limbed lizards that burrow in soil and are poorly studied
Which suborder are snakes?
Serpentes
What are the features of snakes?
No limbs
Excellent olfactory and vibration senses (olfactory organs in roof of mouth known as jacobson’s organs
Pit vipers have a pit organ which senses temperature with 0.003 degrees sensitivity
Fused, transparent eyelids
No external ear openings (unlike worm lizards)
How can worm lizards be excluded from snakes?
Worm lizards have external ear openings
What type of diet do snakes have?
Carnivorous
What percentage of snakes are venomous?
20%
80% of Australian snakes are venomous
Are snakes ovi or viviparous?
Most are oviparous
Which snake has the most toxic venom of all land snakes?
Tiger snake
What superorder are snakes a part of?
Lepidosauria
What order are tuataras a part of?
Sphenodonta
What are the features of tuataras?
1 genus remains
Nocturnal, live in burrows associated with nesting sea brds
Most primitive living reptiles, similar to 200 million year old fossils
Have a primitive third eye on the top of their head used to regulate sun exposure
What are the differences between alligators and crocodiles?
Crocodiles have a broader snout and visible upper teeth when mouth is closed
Alligators have a narrow snouth and both upper and lower teeth visible when mouth is closed
What are the largest crocodilians?
Salties; they extend up to 7m
What is interesting about crocodilians and birds in relation to dinosaurs?
Crocodilians and birds are survivors of the lineage that gave rise to the dinosaurs and have changed very little in 200 million years
