Question

83. The highest level of organization in Phylum Nematoda is

a. cellular

b. tissue

c. organ

d. none of the above

84. Plathelminths and nematodes are both considered ‘worms’, yet they are placed in different clades or taxonomic groups (see Figure 18.4 on page 373). What is a ‘worm’? Does being a worm mean you are closely related to other worms? Why or why not?  

85. Why does it make sense for a cnidarian to be radially symmetrical?

88. Why does it make sense for a worm to be bilaterally symmetrical?

Answer 1

Ans 1-option (c)- organ

Ans 2- Worm is basically a broad term which is found to include several invertebrate phyla including platyhelminthes, Annelida, Nematoda, etc . It consists of typically a long cylindrical tube like body along with no limbs and no eyes.

Worms are evolutionary closely related .

Ans 3- It makes sense for cnidarians to have radial symmetry since it is advantageous since sensory receptors are found to be distributed all around the body. Radial symmetry is very useful as the animal can just sit and grab over food and also detect threats from all directions.

Ans 4- It makes sense for worms to have bilateral symmetry since due to this symmetry animal moves to its anterior forward and moreover crawls. Also, flatworms are found to sense the darkness or light.