What is a starfish's evolutionary history?

Answer 1

they dont have one, starfish are echinoderms so they dont leave behind any evidence that they evolved from anything. they have and always will be starfish. All animals come from some where, in this case a starfish or sea stars comes from a long line of ancestors. Following the past of an animal isn't always as easy as it would seem, first thing to do is find how the animal on topic works. When a starfish starts it's development they are called ovum, this stage is the first identifiable part it is an unfertilized egg. The next stage is a zygote, this is when the egg is first fertilized and starts it's transformation to the starfish. Then becoming two cells and on to four and eight growing larger, next the egg is a morula looking similuar to a cluster of grapes. Then becoming a blastula, early, middle, and late stages are determined by cell size. Gastrula is when the surfaces push into the interior at a point; larva the last stage until it becomes a full grown starfish, this is a ciliated form in which you can see the mouth, digestive system and anus. After understanding how the life cyle works you can start to understand how the animal came to be what it is. The starfish, an echinoderm characterized by five arms extending from a central disk, lives in salt water even though they are not really fish at all dispite their name. When looking back at a sea star they have been thought to always have been sea stars, they have caused problems for evolutionists. The proof that these creatures have evolved is hardly there at all. Cambrian or fossils show that the echinodermswere already complex creatures, they had many of the features they show today. Scientists think the lack of fossils means they may have had water-vascular systems but no calcite skeleton, meaning they would not have fossilized. Sense they have no fossils there is also no way to prove this, there are milions of soft-bodied creaturs, like jellyfish, that have fossilized. Starfish are unlike many animals in the way that they are able to regenerate lost body parts keeping their five "arms". Even more strange if the sea star is cut in half with enough of the general body left on both peices they can grow into a whole new starfish. This is possible because they can be attacked by preditors they must be able to stay mobile, like some types of lizard that are able to grow back their tails. Not all lizards can grow their tails back like a starfish can grow back their arms. Lizards must do this to mate and keep their territories, starfish must do this to stay alive. Because lizards are more stable than a starfish they leave behind their evidence when they parish, looking back lizards needed to do this so when they are caught they can excape more easily; starfish have the same concept, if a fishman catches them and tries to kill them they are able to keep living. There is the old tale of the fisher man that lost his income to the sea stars and when trying to keep them away he cut them into peices, more and more starfish came until they covered the bottom of his boat and soon took it under by the weight they put on. The moral of this story is to tell you not to use aggrestion as the answer but it also provides good evidences that these animals have been around for a long time. Star fish can have any where from five, most commonly, to forty arms, while these are not found often they prove that star fish have evolved from something. They vary in such size and location it provides more evidence that they used to be much different than they are now. Long ago before studies were formed on them star fish were found and said to have only but one arm, mutation in cells and interbreading caused them to grow more soon the arms reached upwards of tens. This can not be proven or disproved because they have no history, the only real truth can be found in what people have passed down from year to year. Starfish live in shallow water meaning they can die from getting over heated, water tieds going down or even getting hit by boats, people and animals. They have to be able to reproduse quickly, they lay many eggs at once and grow up very fast like many animals. They can also live though many things, they are able to stand humans, animals, and pollution. While they have no always been able to do this, when America was first found the the Europeans they could not stand much and died easily but over the hundereds of years they changed with the time and because more suseptable to problems. Starfish are carnivores, eatting clams, mollusks, oysters, coral reefs, and other sea stars. They can live up to thirty-five years and weigh up eleven pounds. Starfish don't have brains or blood, their nervous systems is spread through their arms and their "blood" is actually filtered sea water.