Read the following passage carefully and answer the given questions.
Theory of Evolution
The evolution of life is a gradual process through which simple organisms are transformed into complex life forms over billions of years. It involves genetic changes, adaptation to the environment, and the emergence of diversity in species. Fossil records provide evidence of extinct life forms and transitional stages. Evolution is influenced by factors such as mutation, genetic recombination, and environmental pressure, shaping the biodiversity we see today. Charles Darwin and Alfred Russel Wallace were pioneering naturalists who developed the theory of evolution by natural selection.
The study of fossils in different sedimentary layers indicates ________.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Geological periods in which they were existed
Fossils are the remains of hard parts of past life found in rocks. Rocks form in layers of sediment, one over the other, so each layer belongs to a particular time in the earth’s history.
Option (1) Geographical periods in which they were existed — Incorrect. “Geographical” refers to places on the earth, not to time. Time in the earth’s history is divided into geological periods.
Option (2) Geological periods in which they were migrated — Incorrect. A fossil in a layer shows when the organism lived, not when or where it moved.
Option (3) Geological periods in which they were existed — Correct. The age of the layer gives the geological period in which the organism lived. Comparing layers shows that different life forms lived at different times; this is the palaeontological evidence for evolution.
Option (4) Geographical periods in which they were migrated — Incorrect. Both parts are wrong: the wrong kind of period and the wrong event.
NCERT Extract:
What Are the Evidences for Evolution? – “… Evidence that evolution of life forms has indeed taken place on earth has come from many quarters. Fossils are remains of hard parts of life-forms found in rocks. Rocks form sediments and a cross-section of earth’s crust indicates the arrangement of sediments one over the other during the long history of earth. Different-aged rock sediments contain fossils of different life-forms who probably died during the formation of the particular sediment. Some of them appear similar to modern organisms (Figure 6.2). They represent extinct organisms (e.g., Dinosaurs). A study of fossils in different sedimentary layers indicates the geological period in which they existed. The study showed that life-forms varied over time and certain life forms are restricted to certain geological timespans. Hence, new forms of life have arisen at different times in the history of earth. All this is called paleontological evidence.”