Following statements are related to slow block to polyspermy in mammals.

A. A First slow block to polyspermy comes When the cortical granules fuse with the egg cell membrane, they release protein-digesting enzymes which is called as ovastacin that modify the zona pellucida proteins.

B. A second slow block to polyspermy comes from the so-called zinc spark, the release of billions of zinc ions that is induced by the entry of the first sperm, these released zinc ions are seen to bind to the egg cell membrane form a “zinc shield” that prevents further sperm entry.

C. A third slow block to polyspermy occurs at the level of the egg cell membrane and involves Juno.

Which of the following is incorrect?

TLS Online TPP Program

#Question id: 8907

#Unit 9. Diversity of Life Forms

The endoskeletons of most vertebrates are composed of calcified

TLS Online TPP Program

#Question id: 8908

#Unit 9. Diversity of Life Forms

According to one hypothesis, the jaws of vertebrates were derived by the modification of

TLS Online TPP Program

#Question id: 8840

#Unit 9. Diversity of Life Forms

There are at least a dozen known species in the extinct genus Lystrosaurus. If each species was suited to a quite different environment, then this relatively large number of species is likely due to

TLS Online TPP Program

#Question id: 8903

#Unit 9. Diversity of Life Forms

Terry detaches the snakelike organism from the fish and uses a knife to cut off its head. In doing so, its brain slides out onto the deck of the boat. Terry peers into the cut end of the head and notices that the brain had lain in a sort of pan-like structure that only partially surrounded the brain. What is the structure Terry is observing, and what is it made of?

TLS Online TPP Program

#Question id: 8900

#Unit 9. Diversity of Life Forms

Which of the following statements about craniates is (are) correct?

1. Craniates are more highly cephalized than are non-craniates.

2. Craniatesʹ genomic evolution includes duplication of clusters of genes that code for transcription factors.

3. The craniate clade is synonymous with the vertebrate clade.

4. Pharyngeal slits that can assist in gas exchange originated in craniates,

5. The two-chambered heart originated with the early craniates.

TLS Online TPP Program

#Question id: 8899

#Unit 9. Diversity of Life Forms

A new species of aquatic chordate is discovered that closely resembles an ancient form. It has the following characteristics: external armor of bony plates, no paired lateral fins, and a suspension-feeding mode of nutrition. In addition to these, it will probably have which of the following characteristics?