critical thinking

Chapter 7
Cephalopods, the squids, octopuses, and allies, show a much higher degree of structural and behavioral complexity than the other groups of mollusks. What factors triggered the evolution of these changes? A rich fossil record among cephalopods shows that once they were very common and even dominant in some marine environments. Now there are only about 650 living species of cephalopods, far fewer than gastropods. In the end, were cephalopods successful? What do you think happened along the way?
Factors that triggered the evolution were the need for movement and a more active hunting lifestyle. Even though now they are sorely outnumbered, I think that cephalopods have been successful. That is why there are still around. The gastropods have such a soft body that they needed something hard to protect themselves, and because they carry around a protective shell, they have better protection. Cephalopods on the other hand, special in quick paced movement and have developed tactics to confuse or harm predators.
Chapter 9
Sea turtles have disappeared from many regions, and one way of trying to save them is to reintroduce them to areas where they have been wiped out. This is done by reburying eggs or by releasing newborn baby turtles on beaches. Why are eggs buried or baby turtles released instead of fully grown individuals?
By releasing newborns or burying eggs, the turtles will live a relatively "normal" turtle life. It is important for baby turtles to make their way down the beach and become familiar with it because years later they will migrate back to their birth location to lay eggs.

Chapter 18
Wastes from duck farms used to wash into two shallow-water bays on Long Island, New York. The wastes, rich in nutrients such as nitrate and phosphate, polluted the water. What do you think suppose was the immediate effect of the pollutants? Can you speculate on the likely effects on the comerically valuable shellfish of the area?
Since nutrients such as nitrate and phosphate are waste products, it did not have a very positive effect on the environment. Shellfish are filterfeeders and the waste in the water made them sick and it had an effect on the economy of the local area since no one wants to eat sick fish.