Oh, and Brad, you make a distinction between macro and micro evolution. What then is bacterial/viral/archaean/single-cell eukaryote evolution? Is it always micro-evolution, even though given its speed can produce massive, massive variation between species in short periods of time? It's like animal evolution on drugs, and has been thoroughly documented. Do you believe in it? Consider that animals start out as single-celled eukaryotes during reproduction - a necessity to pass on genetic information and mutations.
BradCube said:
Also, on a completely unrelated note, this may seem like a ridiculous question but do plants also evolve? All of the explanations I see in texts books and given by other people use animals.
Actually, most of my studies at university revolved around plants and bacteria rather than animals. I found it easier to understand evolution through plants rather than animals because it's easier to track. IMO. Though I did a bit on the homeobox genes in vertebrates and vertebrates - an interesting topic in and of itself.
Let's be clear, though, that animals and plants aren't the only things that evolved into multi-cellular organisms. With the big hit that was eukaryotes (look it up, important), lots of new things evolved from them. Of the 7 distinct things to evolve from eukaryotes, 3 of them are multicellular (plants, fungi, animals), and another 3 have multicellular and unicellulars members, as well as unicellular members that join to become multicellular when they want to reproduce, move, defend or attack/feed. Animal evolution wasn't something unique - lots of things had taken new forms with the evolution of the eukaryotic cell. Fungi are more closely related to animals than they are to plants.
Plant evolution is widely understood, possibly because plants are the biggest part of the biotechnology industry (from all areas - drugs, poisons, foods, fuels etc) and thus get the most funding.
One of the things that makes plants so easy to study, evolutionarily, is perhaps that they have live representatives or close relatives of almost every species that has ever evolved, and only a small number of aesthetic points of diversity (leaves, reproductive parts, stems basically) compared to animals. Also, they are younger than animals, having evolved on land (Whilst animals evolved in the ocean). I will talk about algae as well, of which some are the ancestors of plants, whilst others are completely unrelated, despite
looking like the relatives of plants.
To figure out where plants come from we need to figure out where photosynthesis comes from. The answer is cyanobacteria. These single-celled prokaryotes have evolved the ability to convert some colours of light (depends on the species) into energy; that is, they changed from being reductive as in normal bacteria to oxidative. Here is an example of one:
http://upload.wikimedia.org/wikipedia/commons/thumb/6/64/Anabaena_sperica.jpeg/200px-Anabaena_sperica.jpeg
Note that the strand is comprised of multiple separate cells. Cyanobacteria is responsible for the evolution of animals due to changing the make-up of air on earth - they increased the supply of oxygen available to a level that would support life outside the ocean (where oxygen was dissolved in water). Cyanobacteria are some of the oldest organisms and there's a wide variety of species.
Did plants evolve from cyanobacteria? Nope, not even close, actually. Plants evolved from algae.
Algae are not a species or family or anything like that. Algae are a group of eukaryotic organisms that have evolved multiple times, all having chloroplasts - often into the same shape and form (the multicellular ones, that is). A chloroplast is an entity within a algal or plant cell which can photosynthesise. The chloroplast has
its own DNA and is self-contained. Where did the chloroplast come from and why does it have separate DNA? As you might be able to guess, the chloroplast used to be a cyanobacteria. It was captured through endosymbiosis (a eukaryotic algae essentially ate it, but it survived instead of decomposing), just like mitochondria. DNA comparisons between some cyanobacteria and chloroplasts agree with this theory. Examples of this which exist today are:
http://en.wikipedia.org/wiki/Endosymbiont#Endosymbionts_in_protists
Anyway, despite that lots of algae look like plants, not all are related to plants or even eac-other. The likely candidates which plants evolved from are:
http://en.wikipedia.org/wiki/Chlorophyta
The fact that algae already had sexual reproduction explains why all plants do, too. In fact, the Chlorophyta algae are considered part of the plant kingdom, though most would mean Embryohpyta, an offshoot of Chlorophyta, when they say 'plants'.
As for the rest, it follows fairly simply from this diagram, and you can look up each step in Wikipedia:
http://en.wikipedia.org/wiki/Plantae#Phylogeny
Take notice of how almost every branch in that tree has living representatives, or cousins. Perhaps the biggest missing step is the progymnosperms - the massive moss-like trees that were the most common plant during the dinosaur age. There's plenty of fossil record but unfortunately no living members - but the gymnosperms (under seed plants next to progymnosperms, along with things like flowering plants) and ferns are quite similar to them. Gymnosperms include: cycads, pines, conifers, wollemei pine, Ginko Biloba etc. Gymnosperms are older than flowering plants, which is often apparent by looking at them.
Why can't moss grow tall? Because most species have the very simplest of vascular systems (with some moss managing to grow small 'stems' and branch out a bit, but usually to twice the height of normal moss at most).
Why were algae able to grow taller than moss, then? Because they were in water, so they were more stable - they'd grow even taller, too, if the water didn't constantly snap them off (but this is good, fitness wise, as it's a form of reproduction by splitting).
The most interesting steps in plants which I suggest you look up are, in order of evolution:
Charophyta (essentially algae-like plants)
Liverworts
Hornworts, Mosses (both evolved after liverworts, before the rest of plants, but are sparate groups)
Lycodiphyta (a very interesting group which I saw in the Blue Mountains a few days ago. Looks like a small pine tree, but evolved before them and have since diverged from their ancestors on the main plant tree more than mosses, worts, etc. They are the oldest living vascular plants, at about 420 million years old and have many many extinct species)
Pteridophyta, Gymnosperms, Progymnosperms (ferns and fern allies = Pteridophyta, these three groups evolved all roughly at the same time)
Flowering Plants