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Showing posts from November, 2011

What is the point of evolution in bacteria?

This is yet another question I was asked. The idea was that bacteria aren’t becoming complex organisms “on the way”, so what is the point?
This is like another question often asked by sceptics “If humans evolved from monkeys, how come there are no monkeys becoming humans nowadays?” The Earth is a rich place, rich with resources, rich with diversity. Humans did not evolve from monkeys, it’s not like monkeys are living in the past and we are living in the present. We all live in the present, and monkeys have spent time evolving like we have. Monkeys are adapted to their environment, and we are to ours, and bacteria are to theirs. Could you live off bananas, in a tree? Could you turn water, carbon dioxide and light into food? No. There are many different niches on Earth, each of which is inhabited by different organisms. Hot springs, dry deserts, deep oceans, high mountains and an airplane are all very different places. Why would there only be one species?? We are complex for our enviro…

Is evolution in bacteria different to that in primates?

I got asked a question yesterday on Facebook on whether evolution in bacteria and primates differs. The short answer is no.
The long answer is that the process of evolution itself is so simple in a way that it really doesn’t matter what its object is, i.e. what it operates on. It’s easier to understand this if you think about atoms. The forces governing their behaviour are equal properties in different measures. Mass is mass, whether it’s zero or one hundred units. The slight differences in these properties can lead to huge noticeable differences in final products, just look around.
Natural selection isn’t something that can change depending on what it acts on, be it bacteria or primates. Natural selection is there, and any difference in products is just that. Bacteria and primates are different because of the different evolutionary paths their ancestors took, the different environments and selection pressures that led to their present day evolution.
Another question was whether incr…

The place of intelligence in evolution

Without maybe realising, we think about intelligence as being the ability to perform changes to one's environment. We know dolphins have relatively sophisticated communication, and we refer to them as intelligent. However, they are excellent in their given aquatic environment without trying to change it, or colonise other places (land, air, space; yes, it sounds silly).

This distinction is important because changing one's environment has an impact on the selection pressures themselves, and hence natural selection and evolution. How could inability to breathe underwater be selected against if someone has an oxygen tank to breathe out of? How could inability to find a suitable nesting spot be selected against if a bird can build its own nest? The more a natural environment is manipulated into an artificial environment by organisms, the less its evolution is left to chance, as inheritance shifts from strictly molecular level and DNA, to other levels (cognition, artificial storage…

Directional, stabilising and disruptive natural selection

Variety is the spice of life II

Variety is the spice of life

Natural selection acts on variation between organisms. In fact, evolution itself would be impossible without variation. If you have a population where most or all individuals are not varied, then there is no way the population is going to be able to adapt over time, so potential for change doesn’t exist. Adaptation can’t arise spontaneously just because it is needed.
For example, the case of the black and white moths during a time when tree trunks were painted white is a good illustration of this principle. You start with an even variation of about 50-50 between black moths and white moths. The tree trunks get painted white, so clearly the black moths will contrast highly with the white trunks. They are visible to predators, and so most die out, don’t get a chance to reproduce, therefore don’t pass on the gene (allele) that codes for their black colour. As a result, future generations have few black individuals, and a lot more white ones (as the white moths were well camouflaged so w…

hmmm, and DNA

You know what, I've been getting a ridiculous amount of visitors lately, and I don't know why, cos I haven't been writing much lately. Uni is good, doing DNA stuff at the moment, and I was reading about something quite interesting.

Until relatively recently, species and their ancestry was determined mostly by things such as physical appearance and function, i.e. two species look similar, so they must be closely related. Funnily enough, after DNA technology took off and it was possible to determine how closely related species are to one another, a lot of these associations and assumptions that were wrong could be rectified. That similarly looking species may not actually have a recent common ancestor, and different looking members of the same species share most of their genetic make-up. Look for yourself. Flying squirrels on different continents developed their flying wings in parallel with each other, and don't in fact have a relatively recent common ancestor. 

These d…