Lecture 9 RH - Reptiles Flashcards by Rodwan Halimi

What kind of grouping are amniotes?

Monophyletic group within tetrapods.

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What lifestyle do amniotes have?

A terrestrial lifestyle; some colonised air and some returned to water

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What type of fertlization do amniotes have?

Internal fertilization

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What kinds of animals are the amniotes?

Reptiles/Birds

Mammals

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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

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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

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Why is the shell of an egg porous?

Shell contains pores so that the embryo could breath

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What does the layer between the egg’s shell and the chorion contain?

Albumin

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In what order does everything happen with egg production?

fertilization -> membranes around embryo -> shell

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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

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How many occipital condyles do reptile skulls have?

1; compared to 2 in mammals

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Are reptile and fish scales homologous?

No, reptilian scales are epidermal whereas fish scales are mesodermally derived (from the dermis of the skin)

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What is the function of reptile scales?

Physical protection and prevention of dessication

Some reptiles have bony dermal plates with added strength

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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.

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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.

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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.

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What developments in the reptiles have allowed more efficient metabolism to take place?

More effient circulatory system with 4 chambered hearts.

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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

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How long ago did amniotes arise from amphibians?

300 mya

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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

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What basis is there for amniote division?

Skull structure

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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