Evolution question

[Dory]

If bacteria is so adaptable and can survive so easily and in the harshest of condition, why did multicellular organisms, let alone humans have bothered to evolve?

I mean,..think about it... If giant meteors are gonna strike earth, they'll be the only species to survive...why/how the heck did we evolve if they're far more of survivors than us?

[Twiglet]

If bacteria is so adaptable and can survive so easily and in the harshest of condition, why did multicellular organisms, let alone humans have bothered to evolve?

I mean,..think about it... If giant meteors are gonna strike earth, they'll be the only species to survive...why/how the heck did we evolve if they're far more of survivors than us?

Evolution relies on the idea of favourable mutations, so presumably, if a 2 celled organism "happened" and was more efficient at collecting food and reproducing than a one celled one, then it would create more offspring and guzzle up more available resources.

Of course, most 2 cell mutations would be useless, only favourable mutations are successful over time.

Survival depends on conditions, so arguing that bacteria can surivive a meteor strike better than humans is only a condition when a meteor strike happens. Which isn't very often on a big scale. In fact this very argument is used to explain why mammals became dominant as warm-bloods are better adapted than cold bloods to surviving cooling.

There's another aspect of your argument worthy of consideration. Most large organisms (like humans) are a veritable garden of flora and fauna, relying on symbiotic relationships with billions of tiny organism to get by (like e-coli in digestion). Larger lifeforms are life support mechanisms for all kinds of other organisms too.

[Animavore]

If bacteria is so adaptable and can survive so easily and in the harshest of condition, why did multicellular organisms, let alone humans have bothered to evolve?

I mean,..think about it... If giant meteors are gonna strike earth, they'll be the only species to survive...why/how the heck did we evolve if they're far more of survivors than us?

The answer lies in the fact that bacteria have to battle and out compete each other and not just the natual conditions. A lot of bacteria eat or absorb other bacteria.

[Gawdzilla Sama]

Remember, the rule is "Fit to Survive", not "Survival of the Fittest". The 2cell critters survived, and mutants accumulated from there.

As for chances of mutations:

Trillions of 1cells living at any one time. ~1.5 billion years when they ruled the planet. (And they're still around, still having chances to mutate.)

Many trillions, over 1.5 billion years. That comes to . . . many chances to mutate.

[ChildInAZoo]

Plus remember: compared to bacteria, we're barely surviving. Multicellular organisms found a niche, but one that we have to hang on to by our fingernails.

[Gawdzilla Sama]

Plus remember: compared to bacteria, we're barely surviving. Multicellular organisms found a niche, but one that we have to hang on to by our fingernails.

On shear number, 1cells rock!

[Dory]

If bacteria is so adaptable and can survive so easily and in the harshest of condition, why did multicellular organisms, let alone humans have bothered to evolve?

I mean,..think about it... If giant meteors are gonna strike earth, they'll be the only species to survive...why/how the heck did we evolve if they're far more of survivors than us?

The answer lies in the fact that bacteria have to battle and out compete each other and not just the natual conditions. A lot of bacteria eat or absorb other bacteria.

Makes a lot of sense. Thanks.

[PsychoSerenity]

There have been several occasions where most life was wiped off the earth. Most of the species that have ever existed, have gone extinct, only to be replaced by whatever survived.

All the species around today have evolved from lineages that got lucky when the big things happened. If a different branch had been cut off long ago, there might not have been any vertebrates - all the species that evolved from there - fish, birds, reptiles, mammals, might never have existed. But most of the bacteria would still be around.

It could have been a world of Crab People.



(Taste Like Crab, Talk Like People)

[Xamonas Chegwé]

Another thing to consider is the subject of 'niches'. Many organisms survive by adapting to a particular niche - ie. exploiting an environment that others cannot. There are bacteria that can survive in highly acidic, alkaline, heavy metal toxic, hot and cold places - but none of them can survive in ALL of those places. It was only necessary for a multicellular organism to out compete its single celled neighbours in one, highly specialised environment for that species to establish itself.

On the subject of the continued dominance of single-celled thingies, a quote from Dan Dennett's Breaking The Spell sticks with me, "There are about a hundred trillion cells in your body and 90% of them aren't human!"

[beige]

Another thing to consider is the subject of 'niches'. Many organisms survive by adapting to a particular niche - ie. exploiting an environment that others cannot. There are bacteria that can survive in highly acidic, alkaline, heavy metal toxic, hot and cold places - but none of them can survive in ALL of those places. It was only necessary for a multicellular organism to out compete its single celled neighbours in one, highly specialised environment for that species to establish itself.

On the subject of the continued dominance of single-celled thingies, a quote from Dan Dennett's Breaking The Spell sticks with me, "There are about a hundred trillion cells in your body and 90% of them aren't human!"

I was so about to talk about niches, but you stole my thunder

My A level biology experience leads me to believe that niches are among the more important things concerning your question.

http://en.wikipedia.org/wiki/Ecological_niche

[Xamonas Chegwé]

Another thing to consider is the subject of 'niches'. Many organisms survive by adapting to a particular niche - ie. exploiting an environment that others cannot. There are bacteria that can survive in highly acidic, alkaline, heavy metal toxic, hot and cold places - but none of them can survive in ALL of those places. It was only necessary for a multicellular organism to out compete its single celled neighbours in one, highly specialised environment for that species to establish itself.

On the subject of the continued dominance of single-celled thingies, a quote from Dan Dennett's Breaking The Spell sticks with me, "There are about a hundred trillion cells in your body and 90% of them aren't human!"

I was so about to talk about niches, but you stole my thunder

My A level biology experience leads me to believe that niches are among the more important things concerning your question.

http://en.wikipedia.org/wiki/Ecological_niche

Amen to that brother!

Evolution is all about niches - and islands (physical or environmental) - In the phrase, "survival of the fittest", 'fittest' does not mean 'best' - it means better suited to one, very specific, isolated role in its environment. Once you have grabbed a seat that no-one else was thinking of sitting in, it is a lot easier to stay there and make your bum fit better.

[Berthold]

Being bigger does have advantages: Ability to eat the smaller ones, and less danger of being eaten.

[colubridae]

Being bigger does have advantages: Ability to eat the smaller ones, and less danger of being eaten.

More conspicuous. Larger means bad surface to volume ratio.

Up to a point this is useful but can become a problem.

The larger dynos were calculated as being 'warm' blooded'. Their metabolism produced enough heat to keep them warm because of the SA/vol ratio.

The in’s and out’s are so complicated.

I can thoroughly reccomend Douglas Futuyma as a text book (but he can be a bit difficult to read, and obscure) and of course the good Dwaks. Despite the bad press he's received he’s still really good at getting the complex issues of evolution across.

There is a really good explanation for seeming altruism, like alarm calls in bird flocks.

[SevenOfNine]

If bacteria is so adaptable and can survive so easily and in the harshest of condition, why did multicellular organisms, let alone humans have bothered to evolve?

I mean,..think about it... If giant meteors are gonna strike earth, they'll be the only species to survive...why/how the heck did we evolve if they're far more of survivors than us?

This might help:-

Kirill, V. M., V. K. Anastasiya, et al. (2009). "The origin of Metazoa: a transition from temporal to spatial cell differentiation." BioEssays 31(7): 758-768.

For over a century, Haeckel's Gastraea theory remained a dominant theory to explain the origin of multicellular animals. According to this theory, the animal ancestor was a blastula-like colony of uniform cells that gradually evolved cell differentiation. Today, however, genes that typically control metazoan development, cell differentiation, cell-to-cell adhesion, and cell-to-matrix adhesion are found in various unicellular relatives of the Metazoa, which suggests the origin of the genetic programs of cell differentiation and adhesion in the root of the Opisthokonta. Multicellular stages occurring in the complex life cycles of opisthokont protists (mesomycetozoeans and choanoflagellates) never resemble a blastula. Here, we discuss a more realistic scenario of transition to multicellularity through integration of pre-existing transient cell types into the body of an early metazoon, which possessed a complex life cycle with a differentiated sedentary filter-feeding trophic stage and a non-feeding blastula-like larva, the synzoospore. Choanoflagellates are considered as forms with secondarily simplified life cycles.

OR

The origin of metazoan development: a palaeobiological perspective
DOUGLAS H. ERWIN 1
1 Department of Paleobiology, NHB-121, Smithsonian Institution, Washington, DC 20560, U.S.A.

ABSTRACT
The rapid diversification of early Metazoa remains one of the most puzzling events in the fossil record. Several models have been proposed to explain a critical aspect of this event: the origin of Metazoan development. These include the origin of the eukaryotic cell, environmental triggers, key innovations or selection among cell lineages. Here, the first three hypotheses are evaulated within a phylogenetic framework using fossil, molecular and developmental evidence. Many elements of metazoan development are widely distributed among unicellular eukaryotes, yet only 3 of the 23 multicellular eukaryotic lineages evolved complex development. Molecular evidence indicates the lineage leading to the eukaryotic cell is nearly as old as the eubacterial and archaebacterial lineages, although the symbiotic events established that the eukaryotic cell probably occurred about 1.5 billion years ago. Yet Metazoa did not appear until 1000 to 600 million years ago (Myr), suggesting the origin of metazoan development must be linked to either an environmental trigger, perhaps an increase in atmospheric oxygen, or key innovations such as the development of collagen. Yet the first model fails to explain the unique appearance of complex development in Metazoa, while the latter fails to explain the simultaneous diversification of several 'protist' groups along with the Metazoa. A more complete model of the origin of metazoan development combines environmental triggering of a series of innovations, with successive innovations generating radiations of metazoan clades as lineages breached functional thresholds. The elaboration of new cell classes and the appearance of such developmental innovations as cell sheets may have been of particular importance. Evolutionary biologists often implicitly assume that evolution is a uniformitarian, time-homogeneous process without strong temporal asymmetries in evolutionary mechanisms, rate or context. Yet evolutionary patterns do exhibit such asymmetries, raising the possibility that such innovations as metazoan development impose non-uniformities of evolutionary process.

http://mbe.oxfordjournals.org/cgi/conte ... t/14/4/391

http://icb.oxfordjournals.org/cgi/reprint/46/6/683

http://www.pnas.org/content/87/2/763.abstract

[mistermack]

I personally think that one big orgasm is better than hundreds of little ones.