Baby Names Beginning With "S": Meaning: Invincible?

Questions

A robin has nearly 3,000 ----------?

A rodent's teeth never stop growing. They are worn down by the animal's constant gnawing on bark, leaves, and other ----------?

A shrimp has ---------- pairs of legs.?

A shrimp has more than a hundred pairs of chromosomes in each cell nucleus. Man has only ----------?

A single ----------, with its razor-sharp teeth, is still dangerous enough when out of water to rip off the flesh, or a finger or toe, from an unwary fisherman.?