Trees and evolution

[RobertBurden]

Do trees and plants evole like animals? How would a tree learn to develop it's seeds to fall as helicopters to the ground?

[drestie]

Yes, trees and plants do evolve, just like every other living thing.

Organisms don't "learn" to evolve. They just do.
Offspring with beneficial mutations tend to survive and produce more offspring (natural selection), thus changing the gene frequency for that mutation in the next generation. Multiply this by many many generations, and you end up with an species that is different from its ancestors. In a nutshell, that's evolution.

[Clanad]

The good (but relatively novus) Dr., fails to add, in her excellent and concise explanation, that there exists, within the scientific community, currently four definitions of the word species. They are:
1. The Folk Concept of Species
2. The Biological Species Concept
3. The Phenetic (or Morphological) Species Concept
4. Phylogenetic Species Concepts
Each of these major classifications then, usualy, have several sub-defines...
So, the major problem in explaining speciation produced by evolution is; what is a species? Time and space don't permit a discussion of the definitions given, but I think, knowing her integrity, drestie will concur that to state "Organisms don't 'learn' to evolve. They just do" begs the question of when, how and where does one decide a "new" species has arrived?

[drestie]

Absolutely, I agree 100% with clanad, as usual.

The definition of a species and of speciation is extremely difficult. Being a microbiologist, this is even more troubling since none of the above species concepts apply.

But as for plants evolving winged seeds, we don't even need to worry about species definitions, just the changes in gene frequencies (and traits) over time. I think we can agree that the ancestors of maple trees (for example) did not have winged seeds, and the lineage leading to what we now call maple trees evolved winged seeds because the seeds with proto-wings had greater survivorship than those without. Or have I read too much Dawkins recently?

[drestie]

BTW, what the heck is the folk concept? That one is new to me :(

[Clanad]

Here you go, estie:
Naturalists around the world have found that the individual plants and animals they see can be mentally grouped into a number of taxa, in which the individuals are basically alike. In societies that are close to nature, each taxon is given a name. These sorts of folk taxonomies have two features in common. One aspect is the idea of reproductive compatability and continuity within a species. Dogs beget dogs, they never beget cats! This has a firm grounding in folk knowledge. The second notion is that there is a discontinuity of variation between species. In other words, you can tell species apart by looking at them (Cronquist 1988).

Source: Cronquist, A. 1978. Once again, what is a species? Biosystematics in agriculture. Beltsville Symposia in Agricultural Research 2:3-20...

[Clanad]

And... doesn't the classic definition of evolution require speciation?

ev�o�lu�tion (v-lshn, v-)
n.
1. A gradual process in which something changes into a different and usually more complex or better form. See Synonyms at development.
2.
a. The process of developing.
b. Gradual development.
3. Biology
a. Change in the genetic composition of a population during successive generations, as a result of natural selection acting on the genetic variation among individuals, and resulting in the development of new species.
b. The historical development of a related group of organisms; phylogeny

[drestie]

Thanks for that, clanad � definitely a new one to me.

As for your definitions of evolution, I can�t say that I agree with any of them:

1. �usually more complex and better� � perhaps �more suited to it�s current environment� would be more accurate? Better is such a weird word to use here. And as for complexity, this is just wrong. There are many documented cases of organisms losing functions and structures through evolution. I see it in my lab all the time.
2. This is not a biological definition, but it is certainly fine for describing language, galaxies, societies, etc.
3. The first definition is good, until the last few words. Current definitions of evolution do not have to include formation of new species.

Most modern definitions of evolution simply refer to changes in allele frequencies in populations over time. Simple Hardy-Weinberg stuff. So, according to this definition, if in one generation 20% of a population�s gene pool has a particular allele, and in subsequent generations 30% of the population has that allele, evolution has occurred.

My favorite definition (so far) comes from Doug Futuyma: "In the broadest sense, evolution is merely change, and so is all-pervasive; galaxies, languages, and political systems all evolve. Biological evolution ... is change in the properties of populations of organisms that transcend the lifetime of a single individual. The ontogeny of an individual is not considered evolution; individual organisms do not evolve. The changes in populations that are considered evolutionary are those that are inheritable via the genetic material from one generation to the next. Biological evolution may be slight or substantial; it embraces everything from slight changes in the proportion of different alleles within a population (such as those determining blood types) to the successive alterations that led from the earliest protoorganism to snails, bees,

[Clanad]

Good answer, estie... I especially like the Fulbright Fellow, Futuyma, but there's always room for disagreement, no? Good talking to you, by the way...

[drestie]

Of course there is, clanad! I love talking about things like this with knowledgeable people. Thanks for the interesting chat! I look forward to more in the future.