bio 102 ch34 pt2

tetrapods

Vertebrate gnathostomes with limbs and digits; include amphibians, reptiles, birds, and mammals; adapted for life on land with lungs, limbs, and a neck.

amphibians

Tetrapods that typically live a "double life," with aquatic larval stages and mostly terrestrial adult stages; include frogs, salamanders, and caecilians.

Class Amphibia

Class of tetrapods including frogs, salamanders, and caecilians; characterized by moist skin and dependence on water for reproduction.

amniotes

Tetrapods that produce an amniotic egg or retain it internally; include reptiles (including birds) and mammals; adapted for fully terrestrial reproduction.

amniotic egg

Egg with protective membranes (amnion, yolk sac, chorion, allantois) that allows development on land without drying out.

amnion

Membrane surrounding embryo that creates a fluid-filled protective environment preventing desiccation.

yolk sac

Membrane that provides nutrients to the developing embryo.

reptiles

A clade of amniotes including lizards, snakes, turtles, crocodilians, birds, and extinct groups; have dry, keratinized skin and lay shelled eggs.

Class Reptilia

Class of amniotes characterized by scales, internal fertilization, and mostly ectothermic metabolism.

ectothermic

Organisms that rely on environmental heat sources to regulate body temperature.

endothermic

Organisms that generate internal metabolic heat to maintain body temperature.

diapsids

Amniotes with two temporal openings in the skull for muscle attachment; include most reptiles and birds.

synapsids

Amniotes with a single temporal skull opening; ancestors of mammals.

lepidosaurs

Diapsid reptiles including lizards, snakes, and tuataras.

archosaurs

Diapsid reptiles including crocodilians, dinosaurs, pterosaurs, and birds.

theropods

Bipedal carnivorous dinosaurs that gave rise to birds.

birds

Feathered, endothermic reptiles adapted for flight; evolved from theropod dinosaurs.

mammals

Synapsid amniotes characterized by hair, mammary glands, and endothermy; include monotremes, marsupials, and eutherians.

Class Mammalia

Class of amniotes with hair, mammary glands, and high metabolic rates; most are endothermic.

mammary glands

Structures in mammals that produce milk to nourish offspring.

monotremes

Egg-laying mammals such as platypus and echidnas.

marsupials

Mammals that give birth to underdeveloped young that complete development in a pouch (marsupium).

eutherians

Placental mammals in which embryos develop fully in the uterus supported by a complex placenta.

placenta

Organ that connects embryo to mother, allowing nutrient, gas, and waste exchange.

primates

Mammals including lemurs, monkeys, apes, and humans; adapted for arboreal life and high cognitive ability.

New World Monkeys

Primates found in Central and South America; typically have prehensile tails.

Old World Monkeys

Primates found in Africa and Asia; lack prehensile tails and include ground-dwelling species.

anthropoids

Group of primates including monkeys and apes with larger brains and more complex behavior.

apes

Anthropoid primates including gibbons, orangutans, gorillas, chimpanzees, bonobos, and humans; lack tails and have large brains.

1 Describe the key adaptive traits that all tetrapods have.

Four limbs, and feet with digits

A neck, which allows separate movement of the head

Fusion of the pelvic girdle to the backbone allows skeletal movement

The absence of gills (except some aquatic species)

Ears for detecting airborne sounds

1a Why is the Tiktaalik fossil considered an important transitional fossil between fish and tetrapods?

It shows both fish traits (fins, gills) and tetrapod traits (neck, limb-like fins, rib structure), showing the transition from water to land.

2 What class do amphibians belong to? What types of animals belong to this clade? How can amphibians be distinguished from reptiles?

Class Amphibia; includes frogs, salamanders, and caecilians; distinguished by moist skin and lack of scales unlike reptiles.

2a Why do amphibians have slimy skin? Describe a typical amphibian life cycle.

Moist skin aids gas exchange

Life cycle includes aquatic larva (tadpole) → metamorphosis → terrestrial adult

2b What are some adaptations amphibians have for terrestrial life? What are limitations?

Adaptations: lungs, legs, moist skin

Limitations: require water for reproduction, weak lungs, prone to dehydration.

2c Why is "amphibian" ("double life") an accurate term?

They live both aquatic (larval) and terrestrial (adult) life stages

They live in water as larvae and on land as adults.

2d Describe adaptations of amphibians, reptiles, and mammals to land.

Amphibians: moist skin + lungs

Reptiles: dry scales + amniotic eggs (Egg with membranes that protect the embryo and let it develop on land without drying out)

Mammals: hair, placenta, endothermy (maintain own body heat)

3 Which groups are amniotes? Describe three terrestrial adaptations shared by all amniotes.

Reptiles (including birds) and mammals;

Adaptations: amniotic egg, keratinized skin/waterproof skin, rib cage + larger lungs

3a How does the amniotic egg enable life on land?

The amniotic egg protects the embryo and prevents it from drying out, allowing development on land without water.

4 Explain the evolutionary trade-off associated with the amniotic egg.

• Advantage: The amniotic egg protects the embryo from drying out and allows development on land, reducing dependence on water for reproduction.

• Disadvantage: It is energetically expensive to produce, so organisms produce fewer eggs and must invest more energy (often including parental care) to ensure survival.

4a Why are amphibians able to produce more eggs than reptiles? Why is parental care important in amniotes?

Amphibians produce simple eggs with less energy cost; amniotes produce fewer eggs so parental care increases survival.

4b Difference between opportunistic vs equilibrium life history?

Opportunistic life history: Produces many offspring, provides little parental care, and relies on high reproductive output; common in unstable or unpredictable environments.

Equilibrium life history: Produces fewer offspring, provides high parental care, and increases offspring survival; common in stable environments.

5 What class do reptiles and birds belong to? Describe reptile adaptations for land.

Reptiles and birds belong to Class Reptilia.

Adaptations include dry keratinized scales to prevent water loss, internal fertilization, shelled amniotic eggs, stronger lungs for air breathing, and efficient water conservation.

5a Explain the evolutionary trade-off associated with the amniotic egg adaptation.

The amniotic egg increases survival on land by protecting the embryo and preventing drying out, but it is energetically expensive so fewer eggs are produced.

5a Why are amphibians able to produce more eggs than reptiles? Why is increased parental care important in amniotes?

Amphibians produce many simple eggs that require less energy. Amniotes produce fewer, more complex eggs, so parental care increases offspring survival.

5b Briefly describe the evolutionary origin of birds. What type of dinosaur are birds thought to be descended from?

Birds evolved from small bipedal theropod dinosaurs.

5bi How are modern birds adapted for flight?

Honeycombed (lightweight/hollow) bones

Wings with keratin feathers

Reduced body weight (they only one ovary and small gonads, no urinary bladder)

Lack of teeth (lighter skull and body)

5bii What do scientists hypothesize might have been the original function of feathers?

Feathers evolved for insulation, camouflage, or courtship display before flight evolved

6 Birds and early mammals survived the mass extinction at the end of the Cretaceous period. What traits helped them survive?

Small size, adaptable diets, ability to regulate temperature, and diverse habitats (burrowing, flying, nocturnal behavior).

7 What clade do mammals belong to? Describe mammalian traits.

Synapsids; hair, mammary glands, endothermy, differentiated teeth, large brains, and parental care.

7a Briefly describe the evolutionary origin of mammals.

Mammals evolved from synapsid reptiles about 200 million years ago during the Jurassic period.

Evolved from synapsid reptiles; jaw bones became middle ear bones.

7b What key characteristics distinguish diapsids and synapsids?

Diapsids = a pair of holes on each side of the skull behind the eye sockets through which muscles pass to attach to the jaw

Synapsids = a single hole behind the eye socket on each side of the skull for attachment of the jaw muscle

7c Distinguish between monotremes, marsupials, and eutherians. Why are most marsupials found only in Australia?

Monotremes lay eggs; marsupials develop in pouch; eutherians develop fully in placenta.

Marsupials are mostly in Australia due to geographic isolation and independent evolution

7d Why are marsupials mostly in Australia?

Geographic isolation after continental drift led to independent evolution.

8 Derived characteristics of primates.

Grasping hands, nails instead of claws, large brains, forward eyes, and complex behavior.

8a What group of primates includes monkeys and apes?

Anthropoids.

8b How do Old World monkeys differ from New World monkeys? Which group shares a common ancestor with apes?

New World: prehensile tails;

Old World: no prehensile tails;

Old World more closely related to apes.

8c Characteristics of apes.

Larger brains, no tail, long arms, short legs, high intelligence, complex social behavior.

9 Derived characteristics of humans.

Bipedalism, large brain, tool use, language, and complex social structures.

9a Why are humans and chimpanzees so different if genomes are 99% similar?

Small genetic differences affect gene regulation and development, leading to large anatomical differences.

9b Which came first: bipedalism or large brains?

Bipedalism evolved first.