Topic 20

Question 1

What are some characteristics for terrestrial life?

Answer 1

internal fertilization

amniotic egg: protect from desiccation (shell, chorion, amnion)
gas exchange (allantois, chorion)
nutrients (yolk)

no need for water to reproduce, full adapted to life on land

copulation and internal fertilization

waterproof skin

muscles associated with rib cage to ventilate lungs

Question 2

What are skull holes?

Answer 2

number of major holes in post-jaw area of skull important in classification of amniotes

diapsid: two holes per side behind eye socket
synapsid: one hole per side, mammals
anapsid: no holes, turtles

holes allow muscles to pass through to jaw to control jaw movement

Question 3

What are some characteristics of non-avian reptilia?

Answer 3

skin protected by thick, dry, keratinous scales (rather than thin, moist skin of amphibians)

shed in sections, as in turtles, or all at once as in snakes and lizards

leathery eggshell: protects from desiccation, a few species are viviparous, with extra-embryonic membranes acting as a placenta

ectotherms: rely upon environmental heat to maintain appropriate temperature (homeostasis), necessary for enzymes to work

behavioral control of body temperature, don’t expend metabolic energy on heating, need only 10% of calories required by mammal of similar size

little parental care of young (except in crocodilians)

Question 4

What is the order squamata?

Answer 4

most species-rich group of extant non-avian reptiles

characterized by: loosely jointed jaws and skull, paired hemipenes in male

lizards have external ear openings (snakes do not)

lizards - well developed limbs

snakes: no obvious external limbs, skeletal remnants of hind legs present in some pythons

Question 5

What is the order crocodilia?

Answer 5

freshwater and marine, all predatory

cannot chew, so either swallow prey whole or spin to rip off chunks

extant species can walk on land, and some can “gallop” for brief distances

males have single intromittent organ (like turtles)

maternal care: lay eggs in nest, guard nest, carry young in mouth, communicate with sound

Question 6

What challenges of terrestrial life have reptiles solved?

Answer 6

gravity
desiccation
respiration (keratinized scales keep moisture in)
respiration (lungs ventilated with rib muscles and 4 chambered heart)
reproduction (amniote egg and internal fertilization, no water required)
locomotion

Question 7

What is the origin of birds?

Answer 7

birds likely evolved from theropods (small, fast dinosaurs)

new fossils: evidence of dinosaurs with feathers

archaeopteryx: shared a common ancestor with modern birds

Question 8

What are the similarities between theropods and birds?

Answer 8

many theropods had feathers

scales: homologous with feather

hollow thin-walled bones, and 20+ other skeletal similarities

similar respiratory systems

musculature, brain, heart, and other organs similar

build nests and incubate eggs

Question 9

What is the class aves?

Answer 9

10,000 extant spp. depending on taxonomy

“modern branch of dinosaurs”

aves (birds), and crocodilians are the extant groups of archosaurs

endothermic (similar to carnivorous theropods), use metabolic energy to maintain body temperature, high rate of metabolism, feather and layer of fat help retain body heat

Question 10

What are the characteristics of modern birds?

Answer 10

1. Feathers: most important synapomorphy
2. Hollow bones
3. Reduced number of forelimb digits
4. Horny beaks that lack teeth
5. Gizzard (muscular part of stomach)
6. Reduced organs

all these adaptations reduce body weight