NCERT Solution Class 12th Biology Chapter – 7 Evolution
| Textbook | NCERT |
| class | Class – 12th |
| Subject | Biology |
| Chapter | Chapter – 7 |
| Chapter Name | Evolution |
| Category | Class 12th Biology Notes |
| Medium | English |
| Source | last doubt |
NCERT Solution Class 12th Biology Chapter – 7 Evolution Notes Evolutionary Biology, Homology, Fossils, Adaptive Radiation discuss Evolution Notes
NCERT Solution Class 12th Biology Chapter – 7 Evolution
Chapter – 7
Evolution
Notes
The study of the history of life forms on earth is called Evolutionary Biology.
The origin of life on earth can be understood only against the background of the origin of the universe especially earth.
The universe is vast. The earth is almost a speck. The universe is about 20 billion years old. The universe comprises huge clusters of galaxies.
The Big Bang theory explains to us the origin of the universe. It states that a singular huge explosion laid the foundation of the universe.
Most scientists believe that the formation of biomolecules preceded the appearance of the first cellular forms of life.
Conventional religious literature tells us that the theory of creation has connotations.
- One, that all living organisms that we see today, were created as such.
- Two, the diversity was always the same since creation and will be the same in the future also.
- Three, that the earth is about 4000 years old.
Charles Darwin concluded that existing living forms share similarities to varying degrees not only among themselves but also with life forms that existed millions of years ago.
According to Darwin, fitness refers ultimately and only to reproduce fitness. Thus, those who are a better fit in an environment, leave more progeny than others. There therefore will survive more and hence are selected by nature. He called it natural selection and implied it as a mechanism of evolution.
Comparative anatomy and morphology show similarities and differences between organisms of today and those that existed millions of years ago. Such similarities can be interpreted to understand common ancestors were shared or not.
The diversity of life forms on earth has been changing over millions of years.
It is believed that variations in a population either due to meiotic recombination during gametogenesis or germ live mutations result in variable fitness in learning fertile progeny.
Branching descent and natural selection are the two key concepts o.f the Darwinian Theory of Evolution.
Hardy-Weinberg Principle states that allele frequencies in a population are stable and constant from generation to generation. The gene pool remains a constant.
Homology is accounted for by the idea of branching descent; study of comparative anatomy, fossils comparative, biochemistry provide evidence for evolution.
The story of the evolution of modern man among the stories of the evolution of individual species is most interesting. It appears to parallel the evolution of the human brain and language.
Evolutionary Biology – Study of history of life forms on earth.
Big Bang Theory – Theory that explains the origin of the universe.
Fossils – Remains of hard parts of life forms found in rocks.
Divergent evolution – In animals, the same structure developed in different directions due to adaptations to different needs.
Homology – It indicates common ancestry.
Adaptive Radiation – The process of evolution of different species in a given geographical area starting from a point and literally radiating to other areas of geography.