Chapter 34: Origin and Evolution of Vertebrates

Question 1

Chordate

Answer 1

• Bilateral symmetry
• Belong to Deutorosomia
• Derived traits include notochord, dorsal, hollow nerve cord, pharyngeal slits or clefts, and a muscular, post-anal tail

Question 2

Notochord

Answer 2

• Longitudinal, flexible rod located between the digestive tube and nerve cord
• Large, fluid-filled cells encased in fairly stiff fibrous tissue

Question 3

Pharyngeal Slits

Answer 3

• Allow water entering mouth to exit body without passing through entire digestive tract

Question 4

Dorsal, Hollow Nerve Cord

Answer 4

• Develops from plate of ectoderm that rolls into tube located dorsal to the notochord
• Unique to chordates; signifies development of brain and spinal cord

Question 5

Importance of muscular, post-anal tail

Answer 5

• Contains skeletal elements and muscles; helps people many aquatic species in the water

Question 6

Lineages of chordates without a head?

Answer 6

Lancelets and tunicates

Question 7

Craniates? Example?

Answer 7

• Chordate with a skull

- Examples include hagfish, lamprey, jawed vertebrates

Question 8

Lampreys and role in chordates history

Answer 8

• Jawless vertebrates
• Various marine/freshwater environments
• Most are parasites
• Primitive fossils resembling lampreys were found that straddle transition to vertebrates

Question 9

Amniotes

Answer 9

• Tetrapods that have a terrestrially adapted egg

- Derived characteristics of amniotes: anioti eg; rib cage to ventilate lungs

Question 10

Tetrapod + Derived Characteristics

Answer 10

• Gnathostjomes + Limbs

- Have limbs with digits; head is separated from body by neck; bones of pelvic girdle are fused to backbone

Question 11

Major (current) hypothesis for jaws?

Answer 11

Evolved from modification of skeletal rods; supported precursor jaw-form

Question 12

Evidence for life to transition onto land?

Answer 12

• Tiktaalik–evolutionary medium between transition from water to land
• Have neck, ribs, eyes on top of head, fin skeleton, flat skull

Question 13

Lateral line system

Answer 13

Organs that form a row along each side of the body and are sensitive to vibrations in the surrounding water

Question 14

Do mammals have amniotic eggs?

Answer 14

Some do

Question 15

Amniotic egg

Answer 15

• Contains four specialized membranes: amnion, chorion, yolk sac, and allantois
• Key for allowing embryo to develop on land
• Slows dehydration of egg in air

Question 16

Amphibian

Answer 16

• “Both ways of life”
• Fertilization is external in most species
• Ectothermic

Question 17

Ectothermic

Answer 17

Absorb external heat as main source of body heat

Question 18

Amphibian

Answer 18

• “Both ways of life”
• Fertilization is external in most species
• Ectothermic
• Eggs lack a shell

Question 19

Ectothermic

Answer 19

Absorb external heat as main source of body heat

Question 20

Reptiles

Answer 20

• Scales that act as barrier
• Most lay shelled eggs on land
• Most are ectothermic

Question 21

Birds

Answer 21

• Derived characteristics: Keratin feathers, lack of urinary bladder, females with one ovary, small gonads, loss of teeth
• Endodermic (maintain body temp. through metabolism)

Question 22

Origin of Birds?

Answer 22

• Likely descended from theropods (carnivorous dinosaurs)

Question 23

Mammals

Answer 23

• Amniotes that have hair and produce milk
• Larger brain
• Differentiated teeth
• Three group: Monotremes, marsupials, eutherians

Question 24

Evolution of Apes

Answer 24

• Diverged from Old World monkeys 25-30 million years ago

Question 25

Derived Characteristics of Humans

Answer 25

• Upright posture + bipedal locomotion
• Larger brains capable of many functions
• Reduced jawbones
• Shorter digestive tract

Question 26

Monotremes

Answer 26

Found only in Australia and New Guinea; represented by one species of platypus and four species echidnas

Question 27

Marsupials

Answer 27

Opossum, kangaroos; have higher metabolic rates and nipples that provide milk+give birth to live young
- placenta

Question 28

Eutherians

Answer 28

• Placental mammals
• Longer pregnancies
• Include primates (thumbs,

Question 29

Eutherians

Answer 29

• Placental mammals
• Longer pregnancies
• Include primates (thumbs)