NCERT Solution for Class 10 Science Chapter 9
Heredity and Evolution
NCERT Books for Session 2022-2023
CBSE Board and UP Board
Exercises Questions
Page No-159
Questions No-8
Explain the importance of fossils in deciding evolutionary relationships.
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Study of fossils helps us to know as to how character/features have evolved in different groups of organisms. We also can find out which organism evolved earlier, and from common ancestors, based on common features.
There are certain animals which became extinct millions of years ago. Fossils of many of such animals give important clues about missing links in the evolutionary relationship. The fossil of archaeopteryx is a good example of missing link. The fossil of archaeopteryx shows characters of birds and reptiles; which suggests that birds have evolved from reptiles. This example shows the importance of fossils in deciding evolutionary relationships.
Fossil provide us evidence about
1. The organisms that lived long ago such as the time period during which they lived, their structure etc.
2. Evolutionary development of species i.e., line of their development.
3. Connecting links between two groups. For example, feathers present in some dinosaurs means that birds are very closely related to reptiles.
4. Which organisms evolved earlier and which later.
5. Development of complex body designs from the simple body designs.
Fossils are the remains of the organism that once existed on earth. They represent the
ancestors of the plants and animals that are alive today. They provide evidences of
evolution by revealing the characteristics of the past organisms and the changes that have
occurred in these organisms to give rise to the present organisms. Let us explain the
importance of fossils in deciding evolutionary history with the help of the following
example.
Around 100 million years ago, some invertebrates died and were buried in the soil in that
area. More sediment accumulated on top of it turning it into sedimentary rock. At the same
place, millions of years later, some dinosaurs died and their bodies were buried on top of
the sedimentary rock. The mud containing dinosaurs also turned into a rock.
Then, millions of years later, some horse-like creatures died in that area and got fossilized
in rocks above the dinosaur fossils.
Sometime later, due to soil erosion or floods in that area, the rocks containing horselike
fossils are exposed.
If that area is excavated deeper, then the dinosaur and invertebrates fossils can also be
found. Thus, by digging that area, scientists can easily predict that horse-like animals
evolved later than the dinosaurs and the invertebrates.
Thus, the above example suggests that the fossils found closer to the surface of the earth
are more recent ones than the fossils present in deeper layers.
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