Which of the following best describes evolutionary biology?

The correct answer is Option (1) → The study of history of life forms on earth

Evolutionary biology deals with how life began on earth and how living forms changed over millions of years. It tells the history of life forms on earth, from the origin of life to the present biodiversity.

Option (1) The study of history of life forms on earth — Correct. This is the book’s own definition: evolutionary biology is the study of history of life forms on earth. To understand it, we also need the story of the origin of life and of the earth itself.

Option (2) The study of fossils preserved in rocks of different ages — Incorrect. The study of fossils is palaeontology. Fossils are remains of hard parts of life forms found in rocks, and they give evidence for evolution. Evolutionary biology uses this evidence, but it is a wider field than the study of fossils.

Option (3) The study of the development of an embryo from the zygote — Incorrect. The development of an embryo from the zygote is studied in embryology. Embryos also give some evidence for evolution, but this is not what evolutionary biology means.

Option (4) The study of the interactions of organisms with their environment — Incorrect. The interactions of organisms with their environment are studied in ecology (Organisms and Populations, Ecosystem). It deals with living organisms today, not the history of life forms.

NCERT Extract:
Evolution – “Evolutionary Biology is the study of history of life forms on earth. … To understand the changes in flora and fauna that have occurred over millions of years on earth, we must have an understanding of the context of origin of life, i.e., evolution of earth, of stars and indeed of the universe itself.”