Theories of Evolution Lecture : 02 for CSIR Life Sciences

Here We study about
The Earth originated from a disc of dust and gas that orbited the young sun, similar to other planets in our solar system:
Solar nebula: The proto-sun contracted and shed a solar nebula.
Planetesimals: Dust particles in the nebula condensed into asteroid-sized bodies called planetesimals.
Protoplanets: Planetesimals collided and grew into Mars-sized protoplanets.
Moon-forming impact: The Earth's final size was achieved after a major collision with another Mars-sized object. This collision created enough energy to vaporize some of the rock and metal from both objects, forming a disc around the Earth. The disc eventually cooled and clumped together to become the moon.
Earth formed around 4.54 billion years ago, which is about one-third the age of the universe. The Earth's early atmosphere was mostly methane, ammonia, carbon dioxide, and hydrogen, with little oxygen. The Earth was mostly molten due to frequent collisions with other bodies, which led to extreme volcanism.
There are multiple theories of evolution, including:
Darwin's theory of natural selection
This theory states that evolution occurs through natural selection, or "survival of the fittest". Organisms that are better adapted to their environment are more likely to survive and reproduce, passing on their traits to the next generation.
Lamarck's theory of acquired characters
This theory states that organisms can pass on physical changes they acquire during their lifetime to their offspring. For example, Lamarck believed that giraffes stretched their necks to reach leaves on taller trees, and that their offspring gradually evolved longer necks.
De Vries' mutation theory
This theory states that new species are formed when an organism's DNA undergoes a sudden and unexpected change.
The Big Bang Theory
This theory states that the universe was created by a huge explosion 20 billion years ago, and that the Earth formed 10 billion years later. The first life form on Earth is believed to have originated around 2,000 million years ago.
Other theories of evolution include: Evolution as such, Common descent, Multiplication of species, Gradualism, and Neo-Darwinism.