Question

of the phylum Echinodermata. L. 17. Prominent spines are found on_ a. Ophiuroidea b. Echinoidea CAsteroidea a Concentricycloidea e. Holothuroidea Figure 31-2 Use the figure to answer the corresponding question(s). + Urochordata (lunicates) Cophalochordata Cephalaspidomorphl= cartilaginous lahes) N nhà nghi. Chondrichthyes Myxini Prish) (ade Pungfishes) Amphibia Repulla Mammalia (ra 18. Refer to Figure 31-2. At which point did lungs evolve? a. 1 b. 2 c. 3 d. 4 e. 5 19. Snakes are most closely related to: a. lizards. b. turtles. c. eels. d. caecilians. e. Synapsids.

Answer 1

Ans: 1) Correct answer is (e) Not all chordates have vertebrae. Explanation: Chordates are defined as having a notochord at some point in their development. A notochord is a cartilaginous rod that runs along the length of the nerve cord, and provides some amount of rigidity to the animal. 2) Correct answer is (d) larva Explanation: The fertilized eggs of urochordates undergo holoblastic and unequal cleavage to form the blastula. The blastula shows upper micromeres and lower macromeres. When the invagination of the macromeres occurs, gastrulation takes place and the structure of gastrula is formed. This gastrula develops into a tailed larva which is called as tadpole larva. The larva exhibits all chordate characteristics. It has a notochord, a dorsal nerve cord, pharyngeal slits and a post-anal tail. 3) Correct answer is (c) The phylum Chordata Explanation: Mouth Anus Dorsal hollow nerve cord Post-anal tail Pharyngeal slits Stomach Notocord Ans 20 : Correct answer is (a) reptiles Explanation : Birds are most closely related to reptiles because the first groups of reptiles evolved about 300 million years ago. About 40 million years later, a group of reptiles called therapsids branched off, which eventually became modern mammals. Other groups of reptiles split off over the next 120 million years, and one branch called the dinosaurs. These dinosaurs were only distantly related to modern snakes, lizards, and turtles, groups that had split off at different times. But 65 million years ago there was a massive extinction event, and all dinosaurs were killed except for a single group of feathered dinosaurs. These evolved over the next 65 million years into modern birds. So we can conclude that birds are closely related to dinosaurs. Ans 19: Correct answer is (a) Lizards Ans 18 : Correct answer is (d) evolution to amphibians. Explanation : Tetrapods evolved from a group of organisms that, if they were alive today, we would call fish. They were aquatic and had scales and fleshy fins. However, they also had lungs that they used to breathe oxygen. Between 390 and 360 million years ago, the descendants of these organisms began to live in shallower waters, and eventually moved to land Ans 17: Correct answer is (c) Asteroidea