Well, Erin, you might have heard that some (especially physicists and mathematicians, who operate with mathematical formulas) don't consider chemistry and biology as science. They look at those two fields as an accumulation of descriptions, observations. They think science should always be based on math. I personally don't agree, well at least not about each division of biology or chemistry, for example genetics uses certain statistic models and distribution of possibilities, so physical chemistry, there are some predictable, reproducable results. That's why I said DNA comparison should make it objective. it will be proved with scientific methods, with facts which might be interpreted only one possible way, providing the result will be comprehendable of course.
But nevertheless this is an opinion.
I personally think this is why medicine is mostly symptomatic. They just look at the book of collected descriptions of symptoms and prescribe medicine which is recommended because some effect was noticed when using it with certain patients. Maybe you will agree it doesn't look very scientific.
As for the faith and science... did you notice how often desirable theory is limiting a vision of explorer and how he/ she uses a selective information while he is preparing article or generalizing. Of course every time when article is written it is considered a good taste and requirement to mention all experiments which gave different and contradictionary results, but they are given very often in the end of the article ( like the article in the discussion) or in smaller fonts.
We are dealing with human nature here and it tends to favor a certain way of thinking, be selective in accumulation of information. I think faith has place in science as well, but a good, healthy ( or not so healthy) competition between different schools in science makes it impossible for a false theory to live forever. But it still might still survive generations, be as long as of human life, our lives and we can live believing in a false theory. If it is false and we are not aware of it, it is belief, isn't' it?
Nevertheless there are dogmatics between scientists too, and resistance to new ideas, new interpretations even cost some lives (genetics in exile in Soviet Union, 1940th, Nikolai Vavilov).
I'm of course aware that faith doesn't need new facts and information at all and stays unchanged with new discoveries unless it is absolutely necessarily.
But fact remains, there are many short cuts for desirable results in science too and many honest, meticulous explorers who were believers: a father of genetics, monk Gregor Mendel for example.
Last edited by sve; May 2nd, 2008 at 12:43 AM.
Another science writer I really like is Carl Zimmer (he has a fun blog here: http://scienceblogs.com/loom/). He writes on more specific topics, like parasites and resistant E. coli. Cool stuff. Check out the left side of his blog for books, cool links, and his gallery of science tattoos.
Actually, pretty much all of ScienceBlogs is good: http://scienceblogs.com/channel/24-hours
For evolution, specifically, I'd check out Pharyngula. Watch out, he's another angry atheist, but his posts on science are very cool and informative. He always blogs about cool stuff.
Another cool blog is ERV, run by a molecular biology grad student: http://endogenousretrovirus.blogspot.com/
She's a little sassy, but I think you can handle it
Sve, I'm not really sure what you're saying. Sorry. It looks to me like you don't really understand how modern science works, but it's hard to tell. If you think medicine is unscientific then I really don't know how to respond. It may once have been based on nothing but hunches, but that certainly isn't the case now.
Scientists already knew they were linked before this. You can just look at the physiological identities of the said two organisms. Their bonestructure are very similair. For example, dinosaurs which walked on two legs and birds both have the so called wishbone, which no other animals have.
So, I might yak a bit about evolutionary theory here. You are warned. But I love science like most people here love art, so I could go on and on and on….
Contrary to popular belief, biology does have a lot of math in it. Me and math don’t get along as well as I’d like, so I won’t go into excruciating detail, but some math is useful.
In the past – and long before Darwin – people had already recognized that life tends to change over time. They called this process ‘evolution’, obviously. Today, we still use the word, and it can refer to big changes and little changes over many different time frames. But since the Modern Synthesis (which was the merging of genetics and evolutionary theory), what we really mean when we say ‘evolution’ now is a change in gene frequency in a population over time. This definition fits what’s actually going on best. And it’s useful because it can refer to big changes – because physical traits are controlled by genes – and small changes. Of course, each individual biologist has their own ‘pet’ definition, but I like this one because it’s simple and it works.
What was I saying? Oh, yeah.
So, evolution can happen in a couple of different ways. Mostly, when people refer to the evolution of some trait, they’re going to be talking about evolution that happens via natural selection. But that’s not the only mechanism of evolution. One mechanism that gets ignored a lot, but is still important, is called ‘genetic drift’.
Genetic drift is important mainly in small populations, and, unlike natural selection, it is random. It works like this: Imagine a small group of animals are stuck on an island. Maybe they’re descended from a larger population on the mainland, etc – doesn’t matter. For any given trait, you can imagine the genetic variation (the frequency of different alleles, or forms of the same gene) that exists in this population. Let’s say that most of the population, say 90% or so, have the ‘A’ form a gene, and the rest (10%) have the ‘B’ form (I’m simplifying here, obviously). Depending on how small the population is, there could only be a few individuals that have the ‘B’ allele. So if you imagine a catastrophic hurricane blows those guys out to sea, or a tree falls on them, or whatever, you’ve suddenly lost all the ‘B’ alleles in your tiny population. Viola! Instant evolution. Your population is suddenly different: when these guys produce offspring the next time, no one will inherit the ‘B’ allele because it’s extinct.
Drift also happens when a small population breaks off from a larger one – the so-called Founder Effect. This is a result of sampling error. You can think of it like this: If you have a large bag of M&Ms, and you blindly pull out 2 or 3, you’re going to get only 2 or 3 of the possible colors, right? Plus, the frequencies of the colors in your sample (say you pulled out two green ones) will not be the same as the frequencies in the larger sample. Your small sample doesn’t represent the ‘genetic diversity’ of the larger sample. Same thing with drift: the genetic composition of the small founder population is rarely going to be the same as that of the larger population. Most often, you lose a lot of the variation in the original, or some rare genes may be over-represented. As a result, the smaller population is genetically distinct from the original one.
And, remember, this is all completely random – totally due to chance, alone.
I think genetic drift is pretty awesome. It’s probably a lot more important than people give it credit for. It’s certainly important to people who are studying rare or endangered species because these organisms are especially prone to drift. And it’s been important in our history, too. There’s good evidence that humans went through several genetic bottlenecks – times when our population size was severely reduced by disease, migration, etc. During these times, genetic drift was probably a powerful force.
I promised you math, right? I’ll get to that in Part II: Natural Selection. I know, I’m excited too!
Keep it going BlueFooted! I'm enjoying reading your posts in this read.
I used to visit IIDB.org a lot for my dailly fix for science discussion. It used to be an amazing site and I learned a quite a bit there just form reading the posts. Sadly it's not quite the same site it once was.
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Also, if you have any questions about anything, please ask. I love to answer questions, even if I don’t always know the answers
Okay, natural selection. Here’s where we need the math…
Evolution via the mechanism known as natural selection is pretty easy to understand: You have a group of organism that vary in terms of some heritable trait. There is differential reproduction – i.e., some individuals leave more offspring than others – with respect to this trait. Let’s say that individuals with trait ‘A’ have more offspring than individuals with trait ‘B’. And these can be almost any traits you want – curly hair vs. straight hair, red vs. green, etc. They can even be just degrees of the same trait: one individual has feathers that are more blue than another, etc. The result of this (assuming the trait is heritable) is that the more favored trait ‘A’ is going to increase in frequency in the next generation.
You can model evolutionary change via selection with a simple equation:
R = h2 x S
This is called ‘the breeder’s equation’ because it’s based on the principles that animal and plant breeders have used for centuries, and it describes evolutionary change in a single trait. Here, h2 is heritability** (which I will talk about in a second), S is selection, and R is the response to selection or the change in the mean value of trait between parents and offspring.
**Heritability is a weird concept. It refers to how much of the variation in an offspring’s trait can be explained by variation in the parents’ traits. Remember, a lot of variation in traits can be explained by environmental factors – not all variation is controlled by genes. And some traits that are obviously controlled by genes are not heritable. The number of legs you have, for example, is controlled by your genes (obviously), but there’s no significant genetic variation for the trait in our population. So the trait, ‘number of legs’, is not heritable. Other traits, like height, are controlled by both genetics and the environment. In this case, there is genetic variation for height, so it is heritable (although not very heritable because the environmental influence is so strong). Entire fields of statistics – linear regression, and Analysis of Variance – were developed just to deal with the problems of heritability.
But, I digress…
You can see how this equation works really easily: When selection is really strong (big S), say when all the individuals with an unfavorable trait die before they can reproduce, then the change in the trait (R) will be large. If the trait isn’t heritable (h2 = 0), there’s not going to be any response to selection (R will also be 0). And so on.
Of course, this equation is only useful for a single trait. If you want to look at more than one trait at a time, you have to bring out the big guns – the multivariate breeder’s equation:
∆z = G x β
∆z (Delta z bar – there should be a little bar over the z) represents the change in mean trait value for a given amount of time – it’s the equivalent to our R, above. G is the variance-covariance matrix of our traits, representing the genetic correlations between them. And β is a vector representing the selection gradient on our traits.
Sounds complicated, right? Yep, it is. I hate this shit
My point is that we can model evolutionary change in more than one trait at a time, so we are able to look at changes across suites of related (or unrelated traits). The reason it’s complicated is because an organism’s traits don’t exist in a vacuum. There are all kinds of correlations between different traits – indicated in our G term, above – that exist for a variety of reasons. So we can’t just ignore how different traits are related when we consider how they change. This is one of the reasons that some traits tend to evolve together, like warm-bloodedness and four-chambered hearts. They are either functionally correlated – so that selection acts on both at the same time – or genetically correlated – so that when selection acts on one trait, the other is sort of dragged along for the ride.
You can see how this gets even more complicated when we consider cases where selection may be acting differently on two different traits that might be correlated. For example, say it’s either good to be fast and striped or slow and blotchy, but not fast and blotchy or slow and striped. Yikes!
And so on, and so on…
There is a mountain of literature and study devoted to studying, modeling, picking apart, examining, and refining the ideas about natural selection. This is just the teeniest, tiniest tip of the iceberg. There are a gazillion tangents I could go on about. Natural selection is a powerful and well-studied force.
Whew! That wore me out. But I’m really excited for the next installment: I get to talk about my absolutely favorite mechanism of evolution, the pimp of mechanisms, Sexual Selection!!!!
http://www.houghtonmifflinbooks.com/...s/monk_garden/Most people know that Gregor Mendel, the Moravian monk who patiently grew his peas in a monastery garden, shaped our understanding of inheritance. But people might not know that Mendel's work was ignored in his own lifetime, even though it contained answers to the most pressing questions raised by Charles Darwin's revolutionary book, On Origin of the Species, published only a few years earlier. Mendel's single chance of recognition failed utterly, and he died a lonely and disappointed man. Thirty-five years later, his work was rescued from obscurity in a single season, the spring of 1900, when three scientists from three different countries nearly simultaneously dusted off Mendel's groundbreaking paper and finally recognized its profound significance.
Most of what bluefooted explained was initially demontrated by Gregor Mendal, a religious monk.
I think treating science as an offense to religion is absolutely absurd.
Generally, it refers to anything that leads to the evolution of reproductive isolation between populations. A speciation event could certainly result from the founder effect, if the event led to such extensive changes in the daughter population that they could no longer interbreed with the original population.
But speciation is such a complicated process. ‘Species’ is a really arbitrary term that doesn’t always work with biological reality. Many of the groups that we consider ‘good’ species can reproduce. And some can even produce fertile offspring. The question is where do you draw the line? Do you consider two populations that could reproduce if you forced them to, but would never do it naturally to be two different species? Do you only consider two populations that are biologically incapable of producing fertile offspring to be two different species? It’s difficult. And the degree of morphological difference or appearance are not always good measures of which two groups will be able to reproduce and which will not.
Speciation can happen in one generation – a lot of plant species are formed this way by polyploidy (doubling or tripling of chromosome number) or by hybridization (observed in frogs) – or it can take many years of separation, followed by the accumulation of small changes in either morphology or behavior.
Uh, a nerdy topic. Let me try to swallow it as a bait in order to start posting around here after so many time of sporadic lurking...
I think that it won't mean much to Feduccia and the other people from the "birds are not dinosaurs" clique. They've always accepted the overall relatedness of these groups. I'm not sure, but I think that it does not places birds anymore firmly precisely into the dinosaur clade than all the anatomical similarities long known, so they probably could still say that a similar result is obtained if we compare proteins from crocodiles and birds, and even accept that dinos (or specifically theropods, they could propose polyphyly) are somewhat closer to birds than to crocs, but they don't need to accept that birds are actually dinos "yet".
They probably could say that T. rex along with a whole good branch of the theropods are flightless post-Archaeopteryx birds, a sort of Diatryma on 'roids, as Feduccia seems to have accepted to be the case with a few dinosaurs, like the ones closely related to velociraptor.
And here I'm again, posting about scientific matters in another board whose main subject is art. I need treatment.
Last edited by Danniel; May 2nd, 2008 at 05:39 PM.
here is a cool documentary related to the subject..........it's a bout 4 winged dinosaur.
Whew! I’m back.
I’m sure you all missed me, right? I just realized I didn’t really talk much about what selection actually is. You guys already know what it is, right?
That’s right: differential reproduction! Yay!
See, evolution isn’t really about ‘survival of the fittest’ or whatever. It’s mainly concerned with reproduction and passing on our genes – genes for traits that ‘work’ or that spread faster are favored. If you don’t survive you can’t reproduce, obviously, but it’s more complicated than that… of course it is! There are two ‘ways’ in which traits (genes) are favored by selection: either they increase your chances of survival (and, therefore, how many offspring you leave) or they increase your reproduction directly (and… how many offspring you leave).
Because we humans like to categorize things, we’ve divided these into two ideas: natural selection (selection on traits that affect survival) and sexual selection (selection on traits that affect reproduction).
In some ways, these two processes are the same: both favor traits (genes) that lead to increased reproduction. But, in other ways, they’re very different. Mostly because natural and sexual selection lead to the evolution of very different kinds of traits. Like, wildly different.
And that is what I want to talk (write) about now…
Sexual selection, bitches!
First, watch this video.
edit: and this one
Pretty awesome, right? That first bird is not only showing off the beautiful shapes and colors made by his plumage, he’s also dancing and singing. Although his lady friend obviously wasn’t impressed, scientists have been impressed by this sort of thing for a long time.
For Darwin, working out his theory of evolution by natural selection – i.e., concerning traits that appear to increase survival – traits like the ones in the video presented a problem. First, they’re bright and attention grabbing, so predators might take notice. Some of these traits even made animals more vulnerable to predators – think of the peacock’s tail. Second, they take a lot of energy and resources to produce, energy that could be better spent doing other things, like surviving. So what’s the deal?
Obviously, Darwin was not an idiot. He knew, just as we all do, that these elaborate traits help animals get lots of mates and reproduce. Therefore, selection should favor them, because anything that leads one creature to have a slight advantage over another in terms of offspring left will be selected. What he didn’t know is why.
The ‘why’ is the important part.
Some of the ‘why’ is obvious: larger antlers, bigger teeth, larger body size, etc will give some males an advantage over others in fights for females. These are all traits that are used in male-male competition. For example, the eye stalks of the stalk-eyed fly:
Or the antlers of the extinct Irish elk, which could be 13 ft across:
The array of beetle horns:
But other traits are more puzzling, and common througout the animal kingdom. The nuptial dress of the male newt:
The bright colors of the male chameleon (sorry for the naked man chest):
why should a male with bluer feathers, or one who sings a more complex song, or dances more awesomely, get more girls?
Well, Darwin thought that females judged these males by some sort of aesthetic standard – the more ‘beautiful’ the male, the more the girls liked him. Although that’s a lot of anthropomorphizing, I don’t think he was that off. Female creatures (and it’s usually the females, but not always) have definite preferences regarding what they want in a mate. And many of the things that they want appear completely arbitrary at first glance.
So, the question is: Why have these ‘arbitrary’ preferences evolved?
And… I’ll try to answer that in the next part, wherein, I continue to derail this thread and will, eventually, talk about art
Last edited by bluefooted; May 9th, 2008 at 02:45 PM.
Bluefooted, have you ever considered running for office?
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http://news.yahoo.com/s/ap/20080509/...g_scientists_2Congress already has a sprinkling of scientists — three physicists, three chemists, a microbiologist and a biomedical engineer. There are also 13 medical doctors, two dentists, three nurses, two veterinarians, a psychologist, an optometrist and a pharmacist.
That's nothing compared with 215 lawyers.
"Physics is a lot more fun than politics because it presents a great intellectual challenge. You're wrestling with the secrets of nature," said Rep. Vern Ehlers, R-Mich., the most senior of the three physicists. "Politics is not hard. It's learning to work with people."
I'd rather be with objective people. I've had enough of emotional retards. That's why I hated High School.
Berry Stomper, I thank you for some of the most enjoyable time I've spent online in a long time.
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Bluefooted, you are a *god* - and I mean that in the most empirical way possible
Last edited by Zaxser; May 10th, 2008 at 07:40 PM.
In case anyone was wondering what the Red Queen has to do with anything. It's the name of an evolutionary hypothesis having to do with (among other things) the evolution of sex. Like actual sexual reproduction.
The basic idea is that asexual organisms have an inherent advantage because they can reproduce much faster than sexual organisms - two times faster than sexual organisms. This is because a single asexual organism produces two clones, each of which will then produce two clones, and so on. While a sexual organism produces, say, one son and one daughter. The son will not produce any offspring directly, only sire the offspring of the female, so this population increases at half the rate. Just based on this, sexual organisms appear to have half the 'fitness' compared to an asexual population. They should be wiped out by asexual organisms. But they're not, obviously.
So, if sex is so costly, why has it evolved and persisted? That's what the Red Queen hypothesis explains. Each generation of an asexual species will be genetically identical to the one before it, barring any mutation. A population of clones is vulnerable because they all have exactly the same strengths and weaknesses. For example, let's say a virus invades and exploits a feature of this population that every individual shares. In very little time, the entire clone population will be wiped out. The only way around this is to somehow introduce genetic variability.
The Red Queen idea comes from a quote from, that's right, the Red Queen in Through the Looking Glass by Lewis Carrol. She says, "It takes all the running you can do, to keep in the same place." The idea is that in order to just survive against your predators, parasites, and competitors, you've got to keep changing.
Sexual recombination - the shuffling of genes during sexual reproduction - is a great way to introduce genetic variation and speed up adaptation because it allows beneficial gene combinations to accumulate in individuals. Let's say mom has good gene A, and dad has good gene B. Well, if they make a kid, there's a chance he'll receive both A and B, making him more 'fit'. Sex also allows for the shuffling of genes to make new beneficial traits, and it can quickly purge 'bad' or deleterious mutations from populations.
Anyway, the Red Queen is just one of several hypotheses about why sexual reproduction has been maintained.
I hate to mention this... but where have all the creationists gone?
maybe we cant hear them over bluefooted's awesomeness...
People who reject evolution for whatever reason (mostly religious reasons) tend to focus on just 2 things:
1. How did the first life appear?
2. How does one species 'turn into' another?
The first question is not really addressed by evolutionary biology at all, so I tend to ignore it. That's more the realm of chemists and physicists. And people are working on it, for sure - it's a huge, cutting-edge area of research.
The second question is just boring, boring, boring to me. First, because it's incredibly obvious that speciation has happened - it just tends to take a lot of time - the details are the interesting part. And, second, because it's only one teeny tiny part of the research and ideas and implications of evolutionary biology.
I mean - and this is always hard for me to articulate, maybe because I'm an 'insider' or maybe because it's just hard - evolutionary biology is so rich, so useful, so productive a field of research, that I don't think most people can appreciate the scope. I am familiar with only a very small, teeny corner of the work that's been done and is being done. And I can only call myself an expert in a tiny little specialized area of evolutionary biology (signal evolution and behavioral ecology). I know the rest is out there, and I've read about it and understand a small part of it, but I'd have to devote my entire existence to reading and studying in order to become relatively proficient in it.
Heck, my husband works in the area of quantitative genetics and population genetics, and I barely understand that. My friend works on co-evolution between plants and their viruses, and I have almost no knowledge of the work that's being done in that field either. The scope of the science is immense.
The theory of evolution by natural selection changed biology forever - it unified everything that we knew, understood, thought we understood, didn't know, observed, etc. It allowed us to make predictions and make sense of things that seemed absolutely impossible to comprehend. And we aren't going back, ever. That doesn't mean the theories won't be refined, won't be tweaked, but evolution is here to stay.
Creationism and its modern offshoot, Intelligent Design, offer nothing but wishful thinking. They offer no predictions, no useful ideas, nothing to test, no projects for graduate students or future scientists to work on. Absolutely nothing of value to science or medicine. There is no 'research' being conducted on these 'theories' because there's nothing there.
Scientists are not trying to hide the 'truth'. We don't have an agenda. We want to know what is true. We want to know what's real. There's no conspiracy against creationism. There's no 'controversy' to teach.
I'm sorry that some people are misinformed and are basically lied to by the people who promote these ideas. And they are lying, trust me.
Aarrrggggghhh!!! Sorry for rambling, again.
Bluefooted - thank you thank you thank you for taking the time to explain all of this! I really hope some people stumble across this information and open their eyes. I have been a fan of Richard Dawkins for a while, who is also an evolutionary biologist (as I'm sure you know!)
Sooo yeah more more more! haha