Firstly that page discusses speciation, which can fall under macro- or microevolution. Regardless, most of the examples discuss human-induced hybrids and their genetic differences/inability to breed with the parents. Some interesting exceptions to this include the Drosophila melanogaster experiment, where a light being on or off during mating affected the stability of... a hybrid.
The plant examples are all about hybridisation mainly because it has been shown to be a major force of change throughout that kingdom's evolutionary history. Plants are much more tolerant of large-scale genomic changes than other organisms, but said changes frequently lead to mating incompatibility with the parent strain due to meiotic disjunctions-- i.e speciation.
As for the other examples, of
course they are all going to discuss hybrids-- the criteria for species separation according to the biological species concept is the inability to generate fertile hybrid offspring from a cross.
I'll have to go through more of their books to decide for myself, but again, speciation can apply to microevolution (I think Darwin referred to the finch beaks as speciation) or macroevolution.
I'm going by talkorigins' definitions, which appear to represent the accepted modern usages of the terms in scientific discourse:
"Microevolution is defined as the change of allele frequencies (that is, genetic variation due to processes such as selection, mutation, genetic drift, or even migration) within a population."
"Macroevolution is defined as evolutionary change at the species level or higher, that is, the formation of new species, new genera, and so forth."
I think the fact that we're disagreeing about the definitions of micro- and macro- evolution here is really pretty representative of the false dichotomy between the two. Evolution is for the most part a contiguous process and not so easily subdivided-- 'macroevolution' is essentially just 'microevolution' writ large. The distinction is there primarily to aid human thought. The situation with taxonomic classification is much the same once you move away from the hard rule of the BSC-- and even that has issues, as illustrated by situations where gene flow occurs between 'species' despite a lack of any direct mating (i.e through an intermediate).
I spent a fair bit of time in a phylogenetics lab last year, and I can assure you that our tidy classifications
really start to break down when you look at the sequence level. We ran into a number of problems with incomplete lineage sorting-- basically some parts of species A's genome were more closely related to species B than C, while others were closer to C than B. It's a complete nightmare if you want everything to fit into neat little divergence trees.
I agree. It seems that the amount of intelligent people keeps going down. Soon the world will be like the movie Idiocracy with Luke Wilson.
The way I see it, we're devolving. I try not to judge people as better or worse than anyone else, but the sorts of people who are most likely to breed these days are the kind of people who would set the human race back by doing so. Musicians and actors who haven't done a hard day's labor ("work" would be deceiving here; labor is more accurate) in their entire life get their choice of the litter while brilliant and/or hard-working people end up dying alone. Not only is that screwed up, it's slowly eliminating intelligence and determination from our genetics. Eventually, we'll end up a breed of apathetic fools who feel they deserve to have everything handed to them. This is already happening to a degree today. Of course, evolution is a slow process, and it tends to balance itself out. The more apathetic fools we have, the more those with intelligence and determination will be able to shine through..
Sorry guys, but this is a really common and very wrong misconception. Average IQ (that is, the value to which IQ scores are normalised each year) tends to increase every generation. See the
Flynn effect. Whether or not the cause of this phenomenon is biological remains debatable, but you can't just make blanket statements about the population getting less intelligent.
I'm not sure why people get this impression of decreasing intelligence. I suspect the idiots are just getting a lot louder-- courtesy of wealthy economies, widespread communications technology and increasing literacy rates. There's also been the rise of hardcore religious fundamentalism in the US (note however that it has been coupled with decreasing numbers of religious people in general).
Another misconception I should address here is the idea of 'devolving'. Evolution is not teleocentric-- it is far from linear, and does not progress 'up' or 'down' or 'towards' something. Natural selection acts to generate organisms which are good at reproducing in the environment they find themselves in, and
nothing else. If they happen to be better-adapted to a greater range of environments in general, or are what we subjectively see as 'better', it is purely an accessory effect.
