The Ecological Pyramid: Breakdown or Reconstruction

[Schröder]

Hey guys, I'm a junior undergraduate and I'm currently undertaking research with my professor. I was working on a response to a very elementary part of biology; The Ecological Pyramid.

Now there is usually the producers at the bottom and the consumers (carnivores or omnivores) at the top. In most textbooks at the high school and college level, it is always written that if anything in between the dominant consumer and the producer is ejected, there will be a breakdown of the pyramind and possible extinctions. But I think that yes, there would be some extinctions but if the dominant consumer is an omnivore, would it not be possible for that species to adapt to an environment that is void of meat and be able to live solely off of greens (leaf, vegatables, e.t.c.)

So instead of:


4th Consumers (Carnivores or OMNIVORES)
3rd Consumers
2nd Consumers
Consumers (Herbivores)
Producers

If the herbivores were ejected then the 2nd and 3rd consumers (assuming they are primarily carnivores) would eventually become extinct but the 4th consumer (assuming its an omnivore e.g. Homo sapiens)would be able to adapt to this environment and there will be a heavy selection pressure for a more green-oriented nutrition.

So instead of a breakdown of the pyrimid , there would be a reconstruction of it.

What do you guys think of this? Outline the flaws so I don't look like a complete jackass in front of my instructers.

Thanks!

[mith]

One question would be whether or not the omnivore can evolve fast enough without dying out first...see they're probably not going to be very efficient at digesting just plants. Maybe they either die because eating celery doesn't provide enough calories or they overgraze and kill off the plant stock.

[Schröder]

Ahhh! Now THAT would be a problem
Thanks!

[AstusAleator]

to the original question:
Well, the relationships in ecology are pretty much never that simple.
IF there was an ecosystem where there was only 1 species representing every trophic level, then yes removing one entire species might cause others to go extinct. That's usually not the case though.

So instead of a breakdown of the pyrimid , there would be a reconstruction of it.

There is always either a "reconstruction" or complete destruction. I think your thesis needs to be refined.


Another thing to consider: If everything but the primary producers and an omnivore are gone, the primary producers will overpopulate in the absence of primary consumers (the omnivore won't be able to put enough pressure on them) and through succession this may lead to a climax community that holds no nutritional value for the omnivore.