The evolution

Version française : Steemit | Busy

Hi Steemiens, happy to see that you read my chronicles, today we will discuss evolution. However, evolution is a very big subject where there are a lot of things to say, it’s a disciplinary of science in full, so this chronicle will be a glimpse that allows me to open on several subjects.

Before we start, I warn you that I don’t go into any debate on creationism and questioning of evolution. Everyone believes what he wants, and my religion is science!

Let’s talk about creationism by the way!

History of evolutionary thought is very old (from Greek and Romans age). Creationism is one of these thoughts which is still relevant. Beginning from finding that evolutionary phenomena description observed in biology, geology, and astronomy are not compatible with religious texts, where the Creator would create all the diversity know nowadays. That to say.

OK let’s focus on our interest, how, from a bacterium, we have now this diversity of species?
Cheminée.png

We can affirm right now that evolution implies changes, these changes are induced by environment conditions (temperature, pressure, …) but not only. And what changes, is the genetic sequence (DNA). We will see how these changes appear soon.

Then we must apply a selection, because it’s cool to produce change but is this change is the right way? This, is the famous natural selection, introduce by C.Darwin. It’s the key mechanism of evolution.
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Natural selection is a good or bad changes filter so, let’s take an example, with our bacteria (living in the ocean), following modification of their genetic sequence we have three different bacteria pools:

[1] His new sequence allows him to survive in temperature upper than 25°C
[2] This bacteria can now divide itself significantly faster
[3] This one can now resist at a higher pressure

These 3 new kinds of bacteria will undergo the natural selection. Let’s see what happening when we turn up the temperature at 26°C: so only bacteria of type 1 would survive in this novel environment because they can adapt to it. Here this is the environment which has the role of the filter.

Now, what happens if we don’t change the environment conditions: so, bacteria of type 2 will become more numerous and in few generation type 1 and 3 bacteria will don’t exist because they were no longer adapt to this environment. Here this is not the environment which has the role of the filter but is the skill of type 2 bacteria to be more competitive than the other bacteria.
On the other hand, bacteria of type 3 will have an advantage in deep-water (where the pressure is higher), although they will no longer exist where type 2 bacteria can survive.

Of course, changes in Nature are subtler.

When a species or an individual, acquire a change which allows him to be more performant in his environment or an environment change which promotes him we say that he increases his fitness. This term defines the ability of a species or an individual to reproduce itself (in a way or another).

This is the fundamental working of evolution, but they are not the only, of courses! The consequence of this evolution which started 3.8 billion of years ago, we have now a rich diversity of species, called the biodiversity (bios which mean "the life" in Greek). Here is the result:

Source : https://www.evogeneao.com/learn/tree-of-life | Humans are just right of the tree.

Source : http://yifanhu.net/TOL/ | Here humans are on left of fungi.

There are different representations of this tree, it’s called a phylogenetic tree (phylon mean race or tribe in old Greek). So, phylogeny is the study of relations ships among individual or species (living or dead), but I will not go further on this disciplinary (not now anyway).

But how we read this tree?

Let’s zoom on a part of the tree for the example.

Source: http://www.chrismadden.co.uk/where-are-we/chapters/chapter-16.html

That is a very simplified tree, but it will be enough for our example. So here, we see the relationships between 5 species of Primates and we can say that:

-Humans are closer to Chimpanzees than Gorillas. OK

-Gorillas are closer to Humans than Orang-Utans. Why? Well, because common ancestor of Humans and Gorillas are closer to Gorillas than the common ancestor of Orang-Utans, Gorillas, and Humans.
Common ancestor is most of the time theoretical species (this is the nodes in the tree), we can say that, from one common ancestor, two (or more) species have been created.

That’s all for the evolution (for the moment), we will have more occasion later to talk about it, don’t forget, everything is linked. I guess you have already some questions like: