Saturday, February 23, 2013

Evolution Definitions

I wrote this post up a while ago in relation to a discussion I was having about evolution.  I posted it on Facebook at the time, but I forgot to put it up here.  So... here it is.  If nothing else, at least I can reference it later.

Not that a million other people haven't done this, but I doubt most anything I post is all that original. I've tried to make sure all terms and definitions are real, accurate, and succinct. I mean brief. Right, I also tried to use as much normal English as reasonably possible.

Evolution - The build up of changes in a species of organism over generations.

Micro evolution - Smaller changes that do not change the "essence" of a family of organisms, and do not cause speciation.

Macro evolution - Larger changes that do change the "essence" of a family of organisms, and/or does cause speciation. This is what my post this morning was about.

Aristotelian essence - "Of Aristotle". In this case, he is credited with creating a whole school of thought around what "it"-ness is, what makes something itself, and not something else. If you're reading this, you might enjoy reading up on it more here.
Also, you now know a 6-syllable word.

Speciation - The point where two populations with the same ancestor can no longer interbreed. All modern dogs can interbreed, but they cannot breed with bears despite the common ancestor.

Ring Species - These are populations that blur the line of speciation. A can breed with B, and B can breed with C, but A cannot breed with C. They get their name from a population breeding and spreading around a valley or an island, in a circle, so that when the two groups meet on the other side they can no longer interbreed, even though they can both still breed with the original population.

An explanation with pictures can be found here.

Mutation - A change in the structure or placement of genes. Common types are:

Deletion - When copying strands of genes, a chunk is skipped and doesn't get copied.
Duplication - When copying strands of genes, a chunk is copied twice.
Translocation - When copying strands of genes, a chunk is copied but put in the wrong place in the strand.

Selection Pressures - Any condition that changes whether a specific trait is negative (reduces reproduction rate), positive (increases reproduction rate), or benign (does not change reproduction rate).

Natural Selection - The primary means of selecting mutations in nature. The traits commonly positively selected here will be related, but not limited to, nutrient collection, energy efficiency, predator deterrence/protection, and mate selection/attraction.

Selective Breeding, aka Artificial Selection - One of the forms of human selectivity. Obvious examples are dog breeds and race horses, or selective plant pollination. Less well known are cases like Aurochs, the predecessor to the modern day cow, and bananas, which are a mutation of the plantain and aren't actually speciated.

"More evolved" - The idea that one species is more adapted than another. This usually involves a lot of judgements about the current environment or applies human values (such as thinking more gooder) to the target species. Because of the subjectivity of the claim, I feel it's generally meaningless. You could argue that it's based on the number of genes present, but that also has problems: what about genes that don't do anything? Anyway, there are plenty of other organisms that have way more genes than humans. These include a plant with 50x more genes, or an ameoba that has >200x more genes than us.

Aneuploidy - Having too many or too few chromosomes. Common examples are Down Syndrome, or XYY males. This was something I cited in this morning's post without knowing the name.

BONUS - No promises about normal English here.
Teleology - Any claim that nature has a goal or intent, in the way that humans do. In this case, that evolution is trying to make the most highly evolved organisms possible. Evolution is thought to be a byproduct of accidental mutations, guided by a selection process of current adaptations in the current environment, rather than a consciousness that has a specific life form in mind.

I normally come across this concept in theology, in the form "God created the universe so that we would be here today." Without knowing God, we cannot know that this was his intent rather than a butterfly-effect, some accidental happenstance from his actions. Assuming of course that God is real, an assumption I don't usually make.

No comments:

Post a Comment