Rise of the Amniotes and Biology of the Squamates

Question 1

What are the characteristic traits of the Amniote clade?

Answer 1

1. Amniotic egg.
2. Internal fertilization.
3. A keratinized integument and integumentary appendages.
4. Ventilation mechanism involving negative pressure aspiration pump.

Question 2

Which 3 extra-embryonic membranes are unique to amniotes?

Answer 2

1, Amnion (Cushions embryo in buffered aqueous environment of the amniotic cavity)

2. Allantois (Heavily vascularized outgrowth of gut, store of nitrogenous waste and site of gas exchange. Forms part of umbilical cord in mammals)
3. Chorion (Envelopes the egg, co-joins with allantois in late development to function in gas exchange. Forms fetal part of placenta in mammals)

Question 3

What are the stages of shell formation in egg-laying amniotes?

Answer 3

1. Oviduct secretes a protein rich aqueous albumen.
2. One or more shell membranes are laid down around albumen.
3. Eggshell is laid down around shell membranes.

Question 4

Why is direct evidence of the origins of the amniotic egg scarce?

Answer 4

Early amniotes likely laid leathery eggs with no hard shell, these do not fossilize easily.

Question 5

Which amniote traits facilitate the evolution of live-bearing?

Answer 5

1. Internal fertilisation
2. Amniotic egg (extra-embryonic membranes provide interface between mother and offspring, usually through a chorio-allantoic placenta)

Question 6

Squamata is an order which encompasses all Lepidosaurs apart from which species?

Answer 6

Tuatara- only living member of the order Rhynchocephalia

Question 7

How many extant squamate species are there?

Answer 7

> 9000

Question 8

Why has squamate phylogeny proven difficult to resolve?

Answer 8

Frequent coevolution within the clade

Question 9

What repeated themes of coevolution are found within the Squamates?

Answer 9

1. Reduction or loss of limbs.
2. Evolution of live-bearing.
3. Evolution of wings for gliding flight.

Question 10

Why are the lifestyles of terrestrial ectotherms inevitably intermittent?

Answer 10

Limitations of behavioral thermoregulation

Question 11

Which mode of predation is thought to be ancestral in snakes?

Answer 11

Constriction

Question 12

What is the purpose of a snakes’ forked tongue?

Answer 12

Used to transfer chemicals from outside onto paired vomeronasal organs in the roof of the mouth. Allows specific venom proteins to be used to track envenomated prey.

Question 13

How do the pit organs of pit vipers detect infrared?

Answer 13

Specialized heat-sensitive ion channels.

Question 14

What is cranial kinesis?

Answer 14

Movement of skull parts relative to one another (excluding jaw).

Question 15

In the two days ofter feeding, the small intestine and ventricular muscle mass of a Burmese python increases by up to how much to accommodate the meal?

Answer 15

40%