Lunnor

Now that I think of it, the question is asked in a rather weird way. Let's forget the herbivore and carnivore part.
I won't say the heterotrophes are older than the autortophes. The heterotroph will have to feed on whatever is produced by the autotrophes or the auto themselves. Without a reasonable sized group of autos, the hetero will simply die. It might be as old as the autos but not likely to be older.
My question is more related to Oolon's post. Do we have a candidate for a " shark" molecule? I guess this kind of question is just too broad and vague.

No you didn't scare me off
I am a microbiology student myself so I know most of the stuff you post already; but it is a nice reply.

lpetrich

The ultimate origin of viruses is still unknown; there are three favorite theories:

* Viruses are parasitic cellular organisms that got reduced to an extreme degree

* Viruses are subcellular self-reproducing mechanisms that somehow got free of their original host cells

* Viruses are extremely early organisms that originated when the first cellular ones did

These are, of course, non-exclusive; the multiplicity of virus architectures suggests multiple origins.

lpetrich

And here's a <a href="http://www.uct.ac.za/microbiology/tutorial/virorig.html" target="_blank">page on the origin and evolution of viruses</a>.

A bit difficult to interpret, but one interesting conclusion is that prokaryotes and eukaryotes have separate sets of virus families.

Non-praying Mantis

Animals can be herbivorous, carnivorous, omnivorous, saprophilic (eats dead matter), and parasitic. All of these are examples of heterotrophs. Evolution of different species specializing between one type of heterotroph and another is quite common. Here is an example to show you how common:

For my master's thesis, I worked with animals called mole crickets. These crickets burrow underneath turfgrass and feed on various things, depending on species. Normally, most crickets and other orthoptera (grasshoppers, katydids, crickets, etc.) are either herbivorous (grasshoppers) or omnivorous (crickets).

I worked with two species in particular of mole crickets, the tawny mole cricket, and the southern mole cricket. Both of these mole crickets are in the same genus (Scapteriscus), and they have many traits in common (compared to other mole crickets), so they are closely related.

The tawny mole cricket is mostly herbivorous, but it will occasionally eat dead matter (we learned of its diet from studies that examined stomach contents), but the southern mole cricket is mostly carnivorous, a rarity for an orthoptera, but it also eats grass roots at times. So even though these species are closely related, they have different diets.

Diet is nothing more than what is "appetizing" to an animal, and can easily change based on behavior. Behavior can, over time, become specialized, and lead to speciation.

NPM