Chapter 34: The Origin and Evolution of Vertebrates

Question 1

What are the 4 characteristics of the phylum Chordata?

Answer 1

• notochord
• dorsal hollow nerve chord
• pharyngeal slits/clefts
• post anal muscular foot

Question 2

What is the notochord?

Answer 2

A longitudinal, flexible rod located between the digestive tube and the nerve cord.
- provides skeletal support throughout most of the length of a chordate

Question 3

How is the notochord adapted in humans?

Answer 3

It is reduced and forms part of the gelatinous disks sandwiched between the vertebrae

Question 4

What are pharyngeal slits?

Answer 4

Slits that allow water to enter into the mouth and exit without having to go through the digestive tract

• in vertebrates these have been modified for gas exchange and are called gills
• in invertebrates these are used for suspension feeding

Question 5

In tetrapods, what do the pharyngeal slits form into?

Answer 5

Parts of the ear and other structures around the head and neck

Question 6

True or false:

In most vertebrates, a more complex, jointed skeleton develops, and the adult fully retains the notochord.

Answer 6

False

In most vertebrates, a more complex, jointed skeleton develops, and the adult retains only remnants of the embryonic notochord.

Question 7

Vertebrates have a skeletal system and a complex nervous system. What have these two features allowed animals to do?

Answer 7

• Capture food

- Evade predators

Question 8

What are the characteristics of the subphylum vertebrata in the phylum chordata?

Answer 8

• Vertebrae enclosing a spinal cord
• An elaborate skull
• Fin rays (aquatic)

Question 9

Cyclostomes is a clade of chordates that have two characteristics, what are they?

Answer 9

• Jawless
• Vertebrates

E.g., hagfishes and lampreys

Question 10

Hagfish and lampreys lack a backbone but are still considered vertebrates. Why?

Answer 10

They have a presence of rudimentary (nonfunctional) vertebrae

Question 11

Gnathostomes is a clade of animals that has what characteristics?

Answer 11

Jawed vertebrates

Question 12

What are characteristics of hagfishes?

Answer 12

• jawless vertebrates
• notochord
• cartilaginous skull
• no backbone
• scavengers/decomposes
• slime glands (to repel predators)

Question 13

What are characteristics of lampreys?

Answer 13

• parasites (latch onto a host)

- cartilaginous segments surround the notochord

Question 14

The first cartilaginous fishes emerged:

a. 250 billion years ago
b. 250 million years ago
c. 455 billion years ago
d. 455 million years ago

Answer 14

d. 455 million years ago

Question 15

The first tetrapods emerged:

a. 365 billion years ago
b. 365 million years ago
c. 420 billion years ago
d. 420 million years ago

Answer 15

b. 365 million years ago

Question 16

The first amniotes emerged:

a. 320 million years ago
b. 320 billion years ago
c. 365 million years ago
d. 365 billion years ago

Answer 16

a. 320 million years ago

Question 17

How did jaws evolve?

Answer 17

By modification of skeletal rods that supported the pharyngeal (gill) slits

Question 18

Who have been the dominant predators in the ocean for 320 million years?

Answer 18

Class chondrichythes: Sharks, skates, rays

In the clade gnathostomes, superclass tetrapoda

Question 19

True or false:

Sharks need to continuously swim so that water moves across their gills

Answer 19

True

Question 20

What are the characteristics of the class chondrichythes in the subphylum vertebrata?

Answer 20

• cartilaginous skeleton evolved secondarily from an ancestral mineralized skeleton
• largest and most diverse group include the sharks, rays and skates

Question 21

What are the characteristics of sharks?

Answer 21

• streamlined body, swift swimmers
• carnivores
• short digestive tract with a ridge called the spiral valve that increases the digestive surface area
• acute senses
• males have clasper fins

Question 22

Osteichthyes is a superclass of what?

Answer 22

Bony fishes

Has two classes:
Ray finned fishes
Lobe-fins

Question 23

Describe the characteristics of ray-finned fishes.

Answer 23

• named for bony rays that support their fins

E.g., tuna, trout, clownfish, ocean sunfish, oarfish, sea horse

Question 24

Describe the characteristics of lobe-fins.

Answer 24

• muscular pelvic and pectoral fins
  > for swimming and walking across substrates
• rod shaped bones

Question 25

What are the 3 lineages of lobe-fins?

Answer 25

Coelacanths
Lungfishes
Tetrapods

Question 26

What are some specific adaptations of tetrapods?

Answer 26

• 4 limbs, feet with digits
• ears for detecting airborne sounds
• neck (movement of head)
• fusion of the pelvic girdle to the backbone
• no gills (except some aquatic species)

Question 27

What are the classes of tetrapods?

Answer 27

Superclass Tetrapoda 
- Class Amphibia
   ~ clade amniota 
        - Class Reptilia 
             - Class Aves
        - Class Mammalia

Question 28

What are characteristics of amphibians?

Answer 28

• eggs require aquatic environment
• moist skin that complements the lungs in has exchange

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