Q14 of 33 Page 1

Why are fossils considered important in the study of evolution? Explain two ways by which age of fossils can be estimated.

Fossils are the impressions or remains of the dead organisms which are found in our remote past. They help in determining the evolutionary relationships among organisms. For example – Archaeopteryx, a fossil bird has some features similar to birds and some to reptiles which prove that birds might have evolved from reptiles. The fossils which are found in deeper layers of the surface of the earth are more ancient organisms as compared to the ones found on the upper layers.

The two ways of determining the age of fossils are:


a. By dating: Where isotope of Carbon (C14) , uranium, potassium or argon is used to determine the age of fossils.


b. Relative method: The fossils which are found closer to earth’s surface are more recent as compared to fossils which are found in deeper layers.


More from this chapter

All 33 →
13

“pH has a great importance in our daily life” explain by giving three examples.

 13

A compound which is prepared from gypsum has the property of hardening when mixed with a proper quantity of water. Identify the compound and write its chemical formula. Write the chemical equation for its preparation. Mention any one use of the compound.

 15

Our government launches campaigns to provide information about AIDS prevention, testing, and treatment by putting posters, conducting radio shows and using other agencies of advertisements.

a) To which category of diseases AIDS belong? Name its causative organism.


b) Which kind of value is the government trying to develop in the citizens by conducting the above kind of programs?

 16

With the help of a labelled circuit diagram wire describe an activity to illustrate the pattern of the magnetic field lines around a straight current carrying long conducting wire.

i) Name the rule that is used to find the direction of the magnetic field associated with a current carrying conductor.


ii) Is there a similar magnetic field produced around a thin beam of moving (a) alpha particles and (b) neutrons? Justify your answer.