Econstudentlog

Stuff (updated)

(After Ed Yong published his latest post, I decided to add a couple of links – Monday, 10 a.m.)

i. Introduction to Evolutionary Biology (TalkOrigins)

I read this yesterday, I’m sure some of you will find it to be useful. Some quotes:

“Populations evolve. [evolution: a change in the gene pool] In order to understand evolution, it is necessary to view populations as a collection of individuals, each harboring a different set of traits. A single organism is never typical of an entire population unless there is no variation within that population. Individual organisms do not evolve, they retain the same genes throughout their life. When a population is evolving, the ratio of different genetic types is changing — each individual organism within a population does not change. For example, in the previous example, the frequency of black moths increased; the moths did not turn from light to gray to dark in concert. The process of evolution can be summarized in three sentences: Genes mutate. [gene: a hereditary unit] Individuals are selected. Populations evolve.

Evolution can be divided into microevolution and macroevolution. The kind of evolution documented above is microevolution. Larger changes, such as when a new species is formed, are called macroevolution. Some biologists feel the mechanisms of macroevolution are different from those of microevolutionary change. Others think the distinction between the two is arbitrary — macroevolution is cumulative microevolution.

The word evolution has a variety of meanings. The fact that all organisms are linked via descent to a common ancestor is often called evolution. The theory of how the first living organisms appeared is often called evolution. This should be called abiogenesis. And frequently, people use the word evolution when they really mean natural selection — one of the many mechanisms of evolution. […]

Evolution can occur without morphological change; and morphological change can occur without evolution. Humans are larger now than in the recent past, a result of better diet and medicine. Phenotypic changes, like this, induced solely by changes in environment do not count as evolution because they are not heritable; in other words the change is not passed on to the organism’s offspring. […]

Evolution is not progress. Populations simply adapt to their current surroundings. They do not necessarily become better in any absolute sense over time. A trait or strategy that is successful at one time may be unsuccessful at another.” […]

Organisms are not passive targets of their environment. Each species modifies its own environment. At the least, organisms remove nutrients from and add waste to their surroundings. Often, waste products benefit other species. Animal dung is fertilizer for plants. Conversely, the oxygen we breathe is a waste product of plants. Species do not simply change to fit their environment; they modify their environment to suit them as well. […]

Natural selection may not lead a population to have the optimal set of traits. In any population, there would be a certain combination of possible alleles that would produce the optimal set of traits (the global optimum); but there are other sets of alleles that would yield a population almost as adapted (local optima). Transition from a local optimum to the global optimum may be hindered or forbidden because the population would have to pass through less adaptive states to make the transition. Natural selection only works to bring populations to the nearest optimal point. This idea is Sewall Wright’s adaptive landscape. This is one of the most influential models that shape how evolutionary biologists view evolution. […]

Sexual selection is natural selection operating on factors that contribute to an organism’s mating success. Traits that are a liability to survival can evolve when the sexual attractiveness of a trait outweighs the liability incurred for survival. A male who lives a short time, but produces many offspring is much more successful than a long lived one that produces few. The former’s genes will eventually dominate the gene pool of his species. In many species, especially polygynous species where only a few males monopolize all the females, sexual selection has caused pronounced sexual dimorphism. In these species males compete against other males for mates. The competition can be either direct or mediated by female choice. In species where females choose, males compete by displaying striking phenotypic characteristics and/or performing elaborate courtship behaviors. The females then mate with the males that most interest them, usually the ones with the most outlandish displays. There are many competing theories as to why females are attracted to these displays.” (In humans, females choose so this could be construed as another bit of dating advice to add to this post…) […]

“Most mutations that have any phenotypic effect are deleterious. Mutations that result in amino acid substitutions can change the shape of a protein, potentially changing or eliminating its function. This can lead to inadequacies in biochemical pathways or interfere with the process of development. Organisms are sufficiently integrated that most random changes will not produce a fitness benefit. Only a very small percentage of mutations are beneficial.”

There’s a lot more at the link. Not all of it belongs in the ‘all people who know anything about evolutionary biology would agree on this 100 percent’-category [one example: “Genes are not the unit of selection (because their success depends on the organism’s other genes as well); neither are groups of organisms a unit of selection. There are some exceptions to this “rule,” but it is a good generalization.” – not everybody ‘in the field’ would agree with that], but most of it is relatively incontestable and it covers a lot of ground; a huge number of key concepts are explained and elaborated upon here. Read it, but don’t start reading it before you’re in a situation where you have a decent amount of time to spare. No matter how well-read you are, unless you’ve actually read this piece before odds are you’ll not know everything which is covered here – for instance, you probably didn’t know that “over half of all named species are insects. One third of this number are beetles.” I know I didn’t. The article was written a while ago, so I decided to check up on the data – here’s what wikipedia has to say about the matter today: “Even though the true dimensions of species diversity remain uncertain, estimates are ranging from 1.4 to 1.8 million species. […] About 850,000–1,000,000 of all described species are insects.” I should probably point out that even though it’s written in a manner-of-fact like way all the way through, he incidentally doesn’t exactly beat about the bush at the end:

“Scientific creationism is 100% crap. So-called “scientific” creationists do not base their objections on scientific reasoning or data. Their ideas are based on religious dogma, and their approach is simply to attack evolution. The types of arguments they use fall into several categories: distortions of scientific principles ( the second law of thermodynamics argument), straw man versions of evolution (the “too improbable to evolve by chance” argument), dishonest selective use of data (the declining speed of light argument) appeals to emotion or wishful thinking (“I don’t want to be related to an ape”), appeals to personal incredulity (“I don’t see how this could have evolved”), dishonestly quoting scientists out of context (Darwin’s comments on the evolution of the eye) and simply fabricating data to suit their arguments (Gish’s “bullfrog proteins”).

Most importantly, scientific creationists do not have a testable, scientific theory to replace evolution with. Even if evolution turned out to be wrong, it would simply be replaced by another scientific theory.”

As can also be inferred from the links at the end, this is not the only post of its kind at TalkOrigins. Go have a look if you’re even remotely interested!

ii. Two figures:

(link).

iii. How far do Danes commute to go to work? Answer: It varies.

The table includes the Danish municipalities with the ten highest and lowest average commuting distances. The distances given in the table are the distances between the homes of the commuters and their workplaces, not the distances travelled on an average day (which would be twice that number). Local or regional wage differentials and corresponding differences in opportunity cost of time definitely plays a role here. Note that ‘distance travelled’ is not necessarily a good proxy for ‘time spent commuting’, especially not when comparing the commutes of people living in urban areas with those of people living in rural areas (ceteris paribus, d(commuting time)/d(pop-density)>0). The numbers are from this new publication by Statistics Denmark, which also included this map of the gender differences across the country (yellow: the average male commute is less than 6 kilometers longer than the average female commute, etc. The darker, the bigger the difference between the genders..):

The national average commuting distance to work is ~20 km (19.7). The male average is 23.4 km, the female average is 15.9 km.

iv. This should all be known stuff to you guys, but in case it’s not:

v. A number: 27.5% of all inmates in Danish prisons are foreign citizens (article in Danish here). Foreign citizens make up about 7,7% of the population. If you look closer, I’m positive both that you’ll find huge variation across countries, and that you’ll also find that some immigrant groups are significantly less likely to commit crimes than are people with Danish citizenship.

vi. The Long, Fake Life of J.S. Dirr. An internet hoax that survived for 11 years, from the very beginning of social medias almost to the present day. Interesting.

vii. Why You Can’t Kill a Mosquito with a Raindrop. Add this one to the list of questions I had never even thought about asking. Fascinating stuff, a few quotes:

“the consequence of getting hit by a raindrop depends on what part of the mosquito’s body takes the blow. Since the insects are so lanky, 75% of hits happen on the legs or wings. This can throw a mosquito into a brief tumble or even a barrel roll, but it recovers without much trouble.

Direct hits to mosquitos’ bodies are a different kind of carnival ride. The speeding raindrops glom onto the insects and propel them downward. Mosquitos captured on camera sometimes fell as far as 20 body lengths while being pushed by a raindrop. For a human, that would be a 12-story drop and a quick ending to the story. But mosquitos are able to pull away sideways from the raindrops and continue on their way, unharmed.

The only danger seems to come if mosquitos are flying close to the ground when they’re hit, leaving themselves too little time to escape. The authors note that one unlucky bug was driven into a puddle and “ultimately perished.” […]

When the heavy drop hits the airy mosquito, it’s almost like hitting nothing at all. And this, the researchers found, is what keeps the mosquitos alive. By offering barely any resistance, a mosquito minimize the force of the collision. The raindrop doesn’t even splatter when it hits. […]

Humans being hurled downward generally black out around 2 or 3 G’s. But a mosquito suddenly driven toward the ground by a raindrop experiences an acceleration of 100 to 300 G’s. The authors note that “insects struck by rain may achieve the highest survivable accelerations in the animal kingdom.””

viii. TV Tropes tips for writers.

June 10, 2012 - Posted by | biology, data, demographics, evolution, genetics, Lectures, medicine, Pharmacology

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