- Cephalopods, the squids, octopuses, and allies, show a much higher degree of structural and behavioral complexity then the other groups of molluscs. 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?
For any amount of evolutionary advancement to such a height in the structural and behavioral complexity of the cephalopods, would require millions of years and several processes of natural selection. My hypothesis on this evolutionary achievement would be either that they were, at one point, at a disadvantage and had to rely on other ways to either obtain food and/or to defend themselves against predators. Yet, in accordance to the fossil record, which in the question states that, “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 that the several species of cephalopods may have died out due to the mass extinction several millions years ago, and that those that survived, may have more species die out because of the competition between one another for food; it is here where my hypothesis may come into play. But in terms of their success, it is both a negative and positive one, for in terms of their diversification, it is a negative because of the amount of species that are currently living today; yet, it is also a positive because of their structural and behavioral complexity that they have gained through the millions of years of natural selection.
1. 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 reburied or baby turtles released instead of fully grown individuals?
According to several theories on how sea turtles find their birth place to lay eggs, though they spend majority of their lives hundreds of miles away from it, is due to the magnetic field that has imprinted itself in their brain during incubation and/or hatching. Therefore, it would be best that the eggs would be reburied instead of re-introducing adults to a new beach.
- Wastes from duck farms used to wash into two shallow-waters bays on
. The wastes, rich in nutrients such as nitrates and phosphate, polluted the water. What do you suppose was the immediate effect of the pollutants? Can you speculate on the likely effects on the commercially valuable shellfish of the area? Long Island, New York
Because of the rich chemicals that contaminated the bay from the results of run-off, there will be two immediate consequences: 1. all the organisms sensitive to slight environmental changes will die quickly and the remaining surviving organisms will be forced to move, 2. those organisms that survive may go through the event of a population explosion where competitive exclusion takes place and later, because of the shortage in the amount of food consumed by the dominant organism, they may die and be forced to move as well.
The shellfish, being greatly affected by the poisoning of the water by nitrate and phosphate rich chemicals through run-off because of their filter feeding properties as a way to capture food, will absorb a great amount of unneeded nutrients making them far too dangerous to consume thus ruining the several shellfish businesses.