Message 121 of 136 (168868) 12-16-2004 9:49 AM

Reply to: Message 97 by robinrohan 12-15-2004 11:47 AM

As requested:

quote:

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The foregoing statements in regard to the inhabitants of oceanic islands, - namely, the fewness of the species, with a large proportion consisting of endemic forms – the members of certain groups, but not those of other groups in the same class, having been modified – the absence of certain whole orders, as of batrachians and of terrestrial mammals, notwithstanding the presence of aerial bats, - the singular proportions of certain orders of plants – herbaceous orders having been developed into trees, &c., - seem to me to accord better with the belief in the efficiency of occasional means of transport carried on during a long course of time… Charles Darwin, Origin of Species, pg 335

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As I mentioned before, biogeography is the study of the distribution of both living and extinct organisms, and of related patterns of variation over the earth in the numbers and kinds of living things. It seeks to answer questions like: why are species distributed around the globe as they are? Why are closely related species found geographically near to each other? Why are continental islands full of terrestrial endemics that are different from anywhere else - but whose nearest relatives are on the adjacent continental masses? Why are oceanic islands filled with endemic birds, insects and plant life, but few if any mammals? In addition, biogeography explains why although a particular type of habitat might occur in several widely scattered places throughout the world, species in one habitat are more closely related to nearby species in other habitats than to species in the same habitat elsewhere. Finally, it explains why species distribution is not uniform around the globe – some 25 regions contain over 70% of all primate and carnivore species diversity, for instance. (Sechrest et al, 2002)

One of the most fascinating aspects of biogeography is the existence of endemics – as Darwin recognized. An endemic species is one that is found in a restricted geographic area and nowhere else – regardless of whether the specific habitat type exists elsewhere. There are two forms of endemicity: neo-endemicity where a novel species has evolved in situ, and paleo-endemicity where the endemic is isolated simply because the continental species from which it arose is extinct. For our purposes, I’ll be dealing with neoendemics – forms that have newly arisen due to their isolation.

The island of St Helena in the south Atlantic presents a beautiful example of neoendemicity. The island is located some 1900 km from Africa and 2900 km from South America. It is volcanic, formed fairly recently by geological timescales, and has never been connected to any continent (it formed from a volcano off the mid-Atlantic ridge). It is completely surrounded by deep sea (about 4200 m), and hence could never have been connected by dry land to either continent – no matter how much sea level fluctuated during a putative flood. Isolated islands such as St. Helena show the action of several of the postulated mechanisms for evolution: ecological release, as colonizers move into vacant habitat; natural selection operating on initial (often minimal) population variation as a myriad of selection pressures create novel forms; and the population ecology mechanisms of dispersal and extinction. When St. Helena was discovered in the 1500’s, there were an estimated 70 species of flowering plants on the island – 60 of which (in ten genera) were endemic only to the island (Cronk, 1989). Two of these plants are extraordinary examples of evolution in action: the gumwood tree (Commidendrum robustum) is a member of the family Asterecidae – sunflowers and daisies – and the cabbage tree (Lachanodes arborea), also Asterecidae, but completely different morphology and habitat than gumwood. Both of these flowers have occupied and adapted to the “tree” niche on the island in the absence of any other plant in that category. Until the arrival of humans, terrestrial vertebrates were limited to four endemic bird varieties, three of which are now extinct. No mammals or reptiles existed on the island prior to the arrival of humans.

Another island, Madagascar, is considered one of the great evolutionary showcases. It is a large chunk of Africa that broke off from the mainland around 120-165 mya. The island is home to a whopping number of endemics, including unique primates (family Lemuridae), 115 endemic bird species (of 250 total species) including several huge flightless varieties – one of which was larger than an ostrich (but totally unrelated), - a single mammalian predator (the fossa) and a family of small insectivores that I consider to be the poster children of evolution: the Tenrecidae.

Tenrecs are a fascinating case, not only because they are terminally cute, but because they show a vast degree of niche adaptation permitted by their relatively predator and competitor-free ride on the island. They quite plainly evolved on the island itself – their nearest living relatives are the golden moles of Africa (Chrysochloridae) – not even the same taxonomic family. Although the fossil evidence is a bit sparse (not unexpected with tiny mammals – the largest can sit on the palm of your hand), it is clear from genetic testing (18s and 12s rRNA, among others, see Douady, et al 2002) that the 23 species of tenrecs (in three genera) all diverged from their common ancestor with the Chrysochloridae some 55 mya. Today, these small creatures have radiated into a myriad of otherwise unoccupied niches, each with its own unique adaptations. There are burrowing tenrecs filling the “mole” niche, ground-dwelling (but not burrowers) tenrecs that are good runners, but poor climbers that hunt ground-dwelling insects, a swimming tenrec that eats crayfish, tenrecs that are fair climbers but poor runners and jumpers, tenrecs that are excellent climbers but not jumpers, and a tenrec that appears to be exploring the glider niche which one researcher described as a “fuzzy superball whizzing through the treetops”. The only conceivable explanation for this incredible variation is ecological release as novel forms evolved to take advantage of unoccupied habitat.

Another aspect of biogeography that lends its strength to evolution is the existence of so-called ring species. It starts with the observation that there is a continuum of variation from one end of a species range to the other – organisms at the extremes often differ from one another in either subtle or very marked ways. The next observation is that some discrete populations at the extremes occasionally differ enough that they can justifiably be considered distinct species. Three of the most common examples are the Ensatina spp salamander complex of California, the greenish warblers ( Phylloscopus spp) of the Tibetan Plateau, and the globe spanning herring gull complex (Larus spp) that extends completely around the world in the northern hemisphere. Where these three examples meet themselves at the end of the ring, the populations cannot interbreed – there’s enough difference that we consider them distinct species. This lends very strong support to Darwin’s argument that the nearest relatives of a species are the adjacent species. Ring species’ populations are capable of interbreeding freely (free gene flow) between adjacent populations, but the ends of the rings aren’t. The only conceivable explanation for this is allopatric speciation, considered to be a major mechanism of evolution: gene flow from one end of the species’ ranges to another is interrupted or minimized to the point that the ends of the chain are distinct under the biological species complex.

Hope this helps. Again, if you have any questions, feel free to ask.

References:

Cronk QCB, 1989, “The past and present vegetation of St Helena” J Biogeo 16:47-64

Douady CJ, Catzeflis F, Kao DJ, Springer MS, Stanhope MJ, 2002 “Molecular Evidence for the Monophyly of Tenrecidae (Mammalia) and the Timing of the Colonization of Madagascar by Malagasy Tenrecs”, Molecular Phylogenetics and Evolution
22:357–363

Sechrest W, Brooks TM, da Fonseca GAB, Konstant WR, Mittermeier RA, Purvis A, Rylands AB, Gittleman JL, 2002 “Hotspots and the conservation of evolutionary history”, PNAS 99:2067-2071

Message 125 of 136 (193944) 03-24-2005 6:10 AM

Is there other processes to which the evolution of living beings can be compared?

What about the devolopment of our transport systems. From the primitive sled to our modern airline aeroplanes and space shutlles.
Submarines and modern ships included. The all had one origin men's laziness . Easier to put burdens on trunks and pul them , than to carry them.

Another evolutionary system to compare evolution too, is the binary computer.

There excist amasing simmlarities between the binary code used by computers and the genetic code used by living beings.

To which extend is evolution a random process? Is it possible to design a digital video camera without any knowlede of

1 Optical physics
2 Negative feedback controll systems
3 Electronics

to name but a few skills.

Richard Dawkins wrote about the Blind Watchmaker.

More appropriate would be The Mindless Programmer.

Come on Software Developers, do you need intelligence to create software? Did mother Nature need intelligence to the develop the program of live , stored in hardware known as RNA and DNA ?

Message 126 of 136 (194467) 03-25-2005 2:47 PM

Reply to: Message 125 by Jydee 03-24-2005 6:10 AM

Well, you can make a computer run a program - such as a genetic algorithm - that makes it's operations analagous to natural selection. But I don't see that the genetic code is any more analagous to binary code than it is to any other form of codified data. Please could you describe the similarities that you mean?

Genetic mutations occur randomly but evolution is not random.

It is not possible to design a digital video camera without this knowledge. But you could design many of the components of a digital video camera without even knowing what a digital camera is. All of the components that make up a digital video camera was designed before anybody had ever seen a digital camera in real life, and many of them were perfected before anybody even conceived of a digital camera. If you want to stretch the analogy betwen the design of industrial objects and evolution, you could say that the components of biological systems are "designed" (or evolved) in a similar way, without any necessary understanding of the larger systems of which they are a part. But I don't see that the human design of useful objects is particularly relevant to a discussion of evolution.

Judging by the frequency with which my computer crashes, you don't need that much intelligence. In fact it's remarkably easy to write a bad program.

Different computer programmers have different styles of coding. Personally I write a few lines of code, test it, make sure it works, write a few more lines, test it, correct bugs that I put in earlier but didn't notice at the time, add a few more lines, test it again, etc. etc. By the time I've finished a large program, I have forgotten what half of the code was originally for. Some of it may well be unnecessary. Some lines of code may never even get used, because they are contained in subfunctions that I decided during the writing of the program that I never actually need to call.

Certainly I don't imagine that a single computer programmer sits down and writes a large program (like a word processor or a spreadsheet or something) having rationally decided in detail how every single line of code is going to work together. I think the description of how I do computer programming is a little more realistic, and is rather pleasantly analagous to the evolutionary process, but only in a superficial way.

Best wishes,

Mick

[edited by Mick to correct dbCode]

This message has been edited by mick, 03-25-2005 02:48 PM

Message 127 of 136 (194787) 03-27-2005 6:52 AM

Reply to: Message 121 by Quetzal 12-16-2004 9:49 AM

Can you help me with the following:

quote:

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Finally, it explains why species distribution is not uniform around the globe – some 25 regions contain over 70% of all primate and carnivore species diversity, for instance. (Sechrest et al, 2002)

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Is region some spatially fixed measurement within this field? I’m having difficulty understanding what the 70% and 25 ‘regions’ actually covers.

Message 128 of 136 (194813) 03-27-2005 10:26 AM

Reply to: Message 127 by Trae 03-27-2005 6:52 AM

I'll try and clarify. A biodiversity "hotspot" is basically a spacially delimited area that contains a statistically significant higher percentage of species overall than a non-hotspot. Although a bit arbitrary, and there's no real specificity as to size, each of these areas is identified by the fact that they are exceptionally high in endemicity - i.e., they contain species found nowhere else on Earth. Let me see if I can post a graphic (from the Sechrest 2002 article I referenced above) that shows what I mean.

Heh, it worked. The top map is primate, the bottom carnivore. As you can see, there is no real size correlation. Although most of the hotspots are clustered around the tropics (as would be expected), that is also not necessarily a criteria - there are plenty of tropical areas that are NOT hotspots, including all of central Africa. The formal definition of hotspot (and there are now 34 recognized regions rather than the 25 Sechrest noted, see Conservationists Name Nine New Hotspots from Feb 2005) relates to endemic plant varieties - to be a hotspot, the region must contain at least 0.5% of the world's plant diversity (not animals - plants represent the productivity base of an ecosystem, and thus are more representative of actual biodiversity than critters would be).

Hope this helps. Let me know if you have further questions.

Message 129 of 136 (194891) 03-28-2005 2:30 AM

Reply to: Message 128 by Quetzal 03-27-2005 10:26 AM

I really like this approach, like rock layers it should be able to explained to someone without a science background.

Thank you.

Message 130 of 136 (196519) 04-03-2005 5:54 PM

Reply to: Message 126 by mick 03-25-2005 2:47 PM

Binary code is a set of instructions that regulate electronic devices ( hardware). Genetic code is a
set of instructions to regulate chemical reactions by creating enzymes . The end result being living
cells

Both use effective symbols to operate. Binary code uses two symbols, “0"s and “1" called bits) to
create 8 letter words (bytes) or multiples thereof ( 8, 16 ,32 , 64 bit systems. ( this is just
touching the basics of binary mathematics , I know there is much more to it) The sequence of the
bits and bytes determine what will happen on the hardware executing the binary code.

Genetic code uses 4 symbols , two purine and two pyrimidine bases to create three letter words or
codons. The sequence of the codons determine the type and sequence of chemical reaction that
will occur in living cells ( the genetic code’s hardware). These reactions will determine the
structure and appearance of the cell , how it will interact with other cells etc.)

You ask about similarities. Here are a few.

1. Both execute programs and store information using the code.
2. Both codes are effectively stored . ( different types of disks in the case of binary code, DNA
and RNA molecules in the case of genetic code).
3. Both codes are easily and effectively accessed when necessary. (Readability).
4. Both codes are easily and effectively copied and duplicated.
5. Both can incorporate and be effected by foreign code ( virusses)
6. Mutations ( read and write errors) can occur in both.
7. Breakages ( lost strings) can occur in both.
8. The presence of malicious code in both types that can combine with code and corrupt
programs (Viruses)
9. The evolvement of object-oriented languages are comparable to the evolvement of genes. The
genetic code is programmed in an object-oriented way. (genes and enzymes being the basic
objects). It is possible to create great programs without creating a single line of new code using
Java beans )

Mutations a random event , but evolution not? ( “Climbing Mount Improbable “ by Stephan
Dawkins?) His arguments can also explain the my referral to a digital camera, but I am still not
convinced that a “blind watchmaker” will be able to assemble it even if all the components are
already available (nature had to manufacture them separately , create a zoom lens without any
optical knowledge etc.). The chances of a mindless engineer and programmer creating a digital
camera is less than a blind watch maker assembling it. I know many believe it to be possible..
What has the highest probability, a mindless engineer creating life and the genetic code or
geological activity (melting rock forming silicon fluid (glass ,other metals etc. )) forming a digital
camera anywhere in the universe.

Are the part about crashing computers etc tongue in the cheek or are you a machine language
programmer?. I definitely didn’t refer to high level language programming but to the following
0110010101010101 (Binary Machine code) and ACTGTA (DNA genetic code).

A last remark. Both codes create unstable ever changing images. A living cell is a constantly
changing image that differs from millisecond to millisecond . The same with the computer
generated image you are looking at. . It is just an illusion that there is a constant non changing
image on the screen.

Regards

J D

Message 131 of 136 (196524) 04-03-2005 6:30 PM

Reply to: Message 130 by Jydee 04-03-2005 5:54 PM

Correct, natural selection that acts upon the mutations is not random.

Mark

Message 132 of 136 (196667) 04-04-2005 12:02 PM

Reply to: Message 130 by Jydee 04-03-2005 5:54 PM

I find your comparison of the evolutionary process to computer code unfortunate, for the following reasons:

1) Computers (i.e. operating systems & the vast majority of applications) do not operate on a 'natural selection' principle, but rather on a set of pre-defined design guidelines. Your average windows procedure is nothing but a huge 'switch' statement, designed to handle all possible events. Unlike the evolutionary process, the OS knows beforehand all possible events that may occur and is designed to act on each eventuality. The process is static, not dynamic like evolution.

2) Computers (bar certain exclusive applications, which themselves imitate biological evolution) do not operate on a 'random mutation' principle. There's always a purpose/goal that needs to be achieved before design begins. There aren't any (professional) programmers who say 'I'll start coding and see what comes out'.

3) The building blocks of programming code (bits) have no inherent properties that dictate their behaviour. The building blocks of life (carbon atoms, hydrogen atoms, et al) do have inherent properties that dictate how they react, group together, etc.

For these reasons alone your 'evolution is like computer coding' premise is a false analogy.

Also:

Message 133 of 136 (196670) 04-04-2005 12:28 PM

Reply to: Message 132 by Legend 04-04-2005 12:02 PM

The difference is IMHO far greater than that. A computer program if well written is designed to handle errors gracefully, but ONLY those errors or problems that have been forseen. As EVERY programmer knows, lusers will be able to find errors and create exceptions far beyond anything the programmers imagined.

Not only is the program static, it is limited in just how well it handles new conditions by the imagination of the designer.

The combination of Random Mutations filtered through Natural Selection has exactly the opposite characteristics. It is totally unbounded and the product is determined not by preplanning but by the errors that happen. As conditions change (which is the functional equivalent of luser actions) evolution reaches into its bag of mutations to find one that might satisfy the new conditions.

IMHO this is the big difference, computer programs are driven by preplanning while life is driven by posthoc patching.

Message 134 of 136 (196702) 04-04-2005 4:47 PM

Reply to: Message 132 by Legend 04-04-2005 12:02 PM

I think he's talking about the fact that if you're viewing this on a CRT monitor, you're not seeing a static image, but rather a sweeping electron beam energizing phosphorus pixels so fast that it paints the whole image upwards of 60 times a second.

LCD displays don't really work that way, I understand.

And if you're viewing a moving image, then you're seeing about 30 different still images a second, which blur into an illusion of motion (persistence of vision, etc.)

Message 135 of 136 (196703) 04-04-2005 5:02 PM

Reply to: Message 131 by mark24 04-03-2005 6:30 PM

Mmmmm... but natural selection itself is "random" to mutation; i.e. there's no purpose behind the selecting environment. We argue that many times to say that "evolution is not purposeful. It doesn't ever necessarily say that organisms become 'better', only more fit for the current, changing environment."

Also, natural selection is not the only principle going on. There are [genetic code? proteins?] that are kept because there is no selection pressure on the code. Furthermore, there are changes that 'piggyback'

I know I'm speaking very roughly, 'cause I'm still not too knowledgeable about it. I think these are vaild points, and I think they allow one to make the argument that "evolutionary processes" are (virtually) random. There's no a priori reason that any organism survived--they all survived only because they were able to survive in the random (as regarded to the organism itself) environment that they were born into.

What do you think?