Why is it that best of both world organisms are all microcopic?

[wasteofo2]

Why is it that "best of both world" organisms are all microcopic?

Some protists can move around and acitvely pursue food and also use photosynthesis for nutrition. Other organisms can respirate aerobically and anerobically. Why is it that these organisms are all relatively simple and never became hugely dominant?

 

[Hurkyl]

What about the venus fly trap?

 

[wasteofo2]

As far as I know, the flytrap is not that common in many environments, only rainforest like ones.

 

[Nereid]

venus fly trap - an elegant solution to nutrient-deficient soils? -> occupies a niche which has few competitors (and would otherwise be 'empty')?

 

[Monique]

Don't forget: we too can respire aerobically AND anaerobically, the latter is not that efficient to produce energy and we don't have a fast way to get rid of the by products (lactatic acid).

Same goes for photosynthesis: not enough energy is produced to sustain an active organism. Thus an organism would largely depend on foraging foods and slowly become less dependent on photosynthesis, finally loosing that ability.

I believe there is evidence that the respiratory chain actually evolved from the photosynthesis mechanism itself, but I'd have to check my textbook..

 

[Phobos]

Originally posted by Monique
Same goes for photosynthesis: not enough energy is produced to sustain an active organism. Thus an organism would largely depend on foraging foods and slowly become less dependent on photosynthesis, finally loosing that ability.

Is there any research on correlations to body size/complexity to a tendency to specialization?

 

[Monique]

Well, there is the power law which states that if the mass (or volume) of an organism increases, it's need for energy increases with 4 power scaling (4-dimensional increase, while the volume increase is 3-dimensional) http://www.the-scientist.com/yr2003/apr/feature_030421.html

So yes, energy requirement per volume goes up when an organism increases in size.

As for your question: what do you mean by specialization? I would call it adaptation.. a small organism can allow itself to be inefficient: it reproduces fast and is only one cell.

 

[wasteofo2]

Originally posted by Monique
I believe there is evidence that the respiratory chain actually evolved from the photosynthesis mechanism itself, but I'd have to check my textbook..

How would that be? Photosynthesis requiers ATP from respiration to work, so if primitive organisms could photosynthesise but not respirate, how would they have been able to get ATP?

 

[Jikx]

Photosynthesis produces net ATP, releases more ATP than it would consume. Wouldn't be much point if it didn't...

But I'm assuming you mean how did it find the ATP to drive the reaction to produce more ATP? If i remember correctly, ATP can be produced in small amounts abiotically.

 

[Phobos]

Originally posted by Monique
As for your question: what do you mean by specialization? I would call it adaptation.. a small organism can allow itself to be inefficient: it reproduces fast and is only one cell.

Evolving less flexibility in morphology, behavior, diet, etc.

Many species go extinct because they become highly successful/well adapted to a particular ecosystem...then the ecosystem changes.

A species that has more cards up its sleeve can adapt faster to a wider range of circumstances. But I wonder if that ability has the cost of discouraging other types of development (i.e., the energy investment goes toward maintaining flexibility rather than some other feature like body size or whatever).

Perhaps what you said about reproduction is the key. As more is invested in the next generation (i.e., fewer offspring, longer path to adulthood), then there is a greater selection pressure to make the offspring fit the specific environment (specialization). Whereas if a species generates enormous numbers of offspring, then its more willing to let chance play a part in survival. Of course, specialization can also be a result of competition (finding an ecological niche).

Not sure where I'm going with this...just thinking out loud.

 

[Phobos]

Originally posted by wasteofo2
Why is it that these organisms are all relatively simple and never became hugely dominant?

FWIW, such microbes can be considered dominant in many ways...population size, diversity, adaptability, range of ecosystems, total biomass, species longevity, etc.

There are more bacteria in the intestines of 1 person than there are total people in the whole world.