Snippets from Chapter 4 of On the Origin of Species

We have learned about "Variation under Nature" and "The Struggle for Existence" in the last two chapters, so now we can look into the combined effect of this two forces "Natural Selection".

Here Darwin talks about that unlike artificial selection, natural selection is able to act on and notice the difference of the "whole machinery of life".

We also read about sexual selection here which is important to note, because sexual reproduction is the major source of variation in individuals

Sexual selection leads to the development of some weapons and defensive structures.

Here the book notes that the individual variations caused by sexual selection lead to the emergence of advantageous offsprings and then to species.

Here the book spends some time talking about asexual reproduction and that even in asexual reproduction, sexual selection is required once in a while to create new variations.

He also mentions here that flowers of asexually reproducing plants are structured to allow for crossing with a distinct individual.

Yeah this is true, the only terrestrial animals the self fertilize are snails, slugs and earth worms.

This actually really interesting because the most successful organism on earth humans evolved on the large Savanahs of Africa competing against many different species.

I think there is a problem with my copy of the book. It is missing some diagrams and tables that are mentioned in the text, but are not available on my copy.

Since species compete with the organisms that they share the most habits with there is more extinction happening within a genus than between genuses. This means that there are more extinctions with in a genus and extinctions of a genus.

The chapter ends with the mention of The Great Tree of Life metaphor.