Secular Pinoy

I just saw this essay while researching Punk-Eek on the internet. Might be of some interest to the guys here.

You can download it from the attached file below, renaming the extension to pdf, or you can follow the link here: http://www.eeb.uconn.edu/Courses/EEB...EvoDevo_00.pdf

Edited to add..

There are more good articles from that website.
http://www.eeb.uconn.edu/Courses/EEB449/

RufusAtticus

Paleontologists use "macroevolution" slightly different than biologists. For the most part, Biologists restrict it to simply the difference between and among higher taxa. However, paleontologists use it to also describe patterns of diversification among higher taxa. Since paleontology has given additional meanings to the term, then it is not wonder that they'd say that it is more that the accumulation of microevolution.

pz

Well, at least some of us non-paleontological biologists also see a distinction between micro- and macroevolution. The Erwin article in the op cites several examples, and concludes with an emphasis on comparative developmental biologists.

RufusAtticus

Do developmental biologists use "macroevolution" to refer to taxonomic patterns?

pz

Not really...taxonomic patterns aren't our bag, so much. Morphological patterns and mechanisms are more our focus, I would think.

RufusAtticus

Here are what I'd consider are (evolutionary) biologists usage of "macroevolution" and "microevolution."

Microevolution: evolution apparent within a species.

Macroevolution: evolution apparent among species.

What if any meaning would developmental biologists add to these?

pz

Ah, I see what you mean. Generally, I think we'd agree.

That definition isn't exactly perfect, though. Some species differences can be accounted for by relatively small changes (such as a simple chromosomal change that makes hybrids non-fertile), and those aren't particularly interesting to an evodevo person. The focus is more on mechanisms of and constraints on morphological change -- how do evolutionary novelties arise, why do some lineages exhibit a greater range of morphological variation than others, what are the intrinsic properties of organisms that permit evolvability or restrict variation.

For instance, one example would be Billie Swalla's work on the molecular mechanisms of tail generation in ascidians. She's looking at the switch that can turn a primary chordate character on and off. Other researchers are looking at how such a complex, defining trait could have initially arisen -- one answer seems to be that tail bud formation might be a fairly simple reactivation of the same program of cell migration responsible for epiboly/gastrulation.

I think the magic words missing from your definitions are "morphology" and "mechanism". Those are the ones evodeviants would like to add, with more clarity than we currently have at our disposal.

Doubting Didymus

I would like to vote the terms macro- and microevolution as the least well understood terms in evolutionary science. How many people think that 'macroevolution' refers to a large scale change in an organism, like a new limb (!) or organ? How many creationists think macroevolution is a shark giving birth to a frog? These ideas are so far off the mark its not funny.

The standard definitions do sod all to help as well. Evolution within species? Evolution between species? What the fuck does that mean? It took me utterly forever to work it out for myself. I hereby find the terms too screwed to live, and motion that they be replaced. (in my dreams)

Oolon Colluphid

From what I have read and argued about with cretinists, insofar as the terms are of any use, microevolution is evolution that goes on within a species -- or population, stuff like rat immunity to Warfarin. Macroevolution is usually not ‘between species’, but simply ‘above the species level’. This is the broader patterns across time: diversifications, mass extinctions etc.

Speciation is the bridge between them, but it’s pointless to draw a line between the two, since evolution is a process, and you can’t draw a line on a process except arbitrarily. Does the micro- that leads from one species to another without branching (anagenesis) come under microevolution, but if there’s branching (cladogenesis) it’s macroevolution? As we know, both cladogenesis plus replacement and, depending on the quality of the fossil record, anagenesis can give the impression of something ‘bigger’ happening in the fossils, which might be called macroevolution.

So personally, as the prefixes imply, I’d use macro- for larger scale stuff, micro- for smaller, and leave the middle grey as just evolution (or actually use the terms above as appropriate).

Cheers, DT

pangloss

Here's the puzzler:

If, say, a single point mutation in a gene that regulaters or influences development causes a major phenotypic change, and the offspring produced is viable and is able to reproduce, would we have an instance of micro or macroevolution?



Therein lies my 'belief' that macroevolution - large phenotypic change - can and most likely is just microevolution in the right spots....