NCERT Book Class 12 Biology Chapter 6 Evolution

BIOLOGY

CHAPTER 6

EVOLUTION

6.1 Origin of Life
6.2 Evolution of Life Forms - A Evolutionary Biology is the study of history of life forms
Theory on earth. What exactly is evolution? To understand the
6.3 What are the Evidences changes in flora and fauna that have occurred over millions
for Evolution? of years on earth, we must have an understanding of the
6.4 What is Adaptive context of origin of life, i.e., evolution of earth, of stars and
Radiation? indeed of the universe itself. What follows is the longest of
6.5 Biological Evolution all the construed and conjectured stories. This is the story
6.6 Mechanism of Evolution of origin of life and evolution of life forms or biodiversity on
6.7 Hardy - Weinberg planet earth in the context of evolution of earth and against
Principle the background of evolution of universe itself.
6.8 A Brief Account of
6.1 ORIGIN OF LIFE
Evolution
6.9 Origin and Evolution of When we look at stars on a clear night sky we are, in a
Man way, looking back in time. Stellar distances are measured
in light years. What we see today is an object whose emitted
light started its journey millions of year back and from
trillions of kilometres away and reaching our eyes now.
However, when we see objects in our immediate
110 surroundings we see them instantly and hence in the
present time. Therefore, when we see stars we apparently
are peeping into the past.
The origin of life is considered a unique event in the
history of universe. The universe is vast. Relatively speaking
the earth itself is almost only a speck. The universe is very