Why do scientists need fossils?

Question

Give 5 examples of organisms scientists have discovered because of fossils.

Answer 1

Geologists use fossil evidence to correllate between rock sequences - they have established that certain fossils only occur in rocks laid down in a particular interval of geologic time, so if they find those fossils (called index fossils) they know how old the rocks are.  This is important in terms of understanding the earth's history.  Fossils also tell us about the sort of environment the rocks were laid down in.

You ask for 5 examples of organisms that have been discovered because of fossils but this is not clear.  Any fossil represents a trace or part of a formerly living organism - so anything that occurs as a fossil but is now extinct could be said to be said to have been discovered because of fossils - trilobites, dinosaurs, crinoids, placoderms, gymnosperm plants and belemnites spring to mind - these groups have no living representatives but were important at various times in earth's history.  

Answer 2

because it helps them understand prehistoric animals and time better.

Answer 3

How about any major dinosaurs, trilobites, primitive reptilian birds (i.e., archaeopteryx), early fish species, and various extinct ferns, trees, and other plants.  That is just scraping the surface, covering a broad array of easy to visualize examples.  There are many thousands of specific organisms discovered because of fossils.

To answer your first question, why scientists need fossils, first consider the following:

Science, by itself, is a new form of what was called natural philosophy.  The idea is that we, as humans, can observe our surroundings.  There are some things that we notice are common, and through science, we try to understand, and then explain, what those things are that we are observing.

Fossils are evident all over the Earth, but they are better preserved in some areas than in others.  Most fossils are preserved well in sandstone formed from ancient river beds and ocean floors.  People who have visited those sites found it easy to locate fossils.  Over time, scientists (those who study fossils) have studied fossils, finding ways to better understand what they are and what their presence means to us.

It is through the observation of fossils that we, as humans, can learn to understand what happened in the days before people could write things down.  It can be fascinating to learn what happened thousands, millions, and even billions of years ago, by simply observing the remnants of those organisms that once existed on the Earth.  By learning understanding the past, we can be better prepared for our future.

I hope that helps you a little.