Why were dinosaurs so large?

[HydrogenBond]

I can see random changes within the DNA as well as natural selection in terms of a species. How does evolution work in the context of all life, since natural selection within one species will have an impact on other species? In other words, all life in eco-systems do not go in separate random directions. Nature forms integrated systems that are also integrated with the environment. These form a delicate balance which means things are in a narrow place within the context of the whole.

 

Is evolution more concerned with individual species taken out of the context of eco-system and environmental integration? Eco-systems are often in delicate balance, meaning a very tight tolerance for sum of the parts. Isn't that implicit of a selective bandwidth for all the different species within that system?

 

Let me do the opposite. Say we begin with an integrated eco-system with a hundred species. Each species begins evolving through random changes in the DNA and natural selection but only relative to that species, with no sense of direction or goal in context of the eco-system. What we will have is all hundred species walking to the beat of their own drum evolving in random directions. This will create an eco-system where none of the parts coordinate.

[Getting A Life]

Not so. If all organisms develop in ways that are not beneficial to other organisms and nothing coordinates then evolution has moved in a direction of disadvantage.

 

The term adapt or die is fitting to evolution. Organisms with the best adaptations for their environments have a higher chance of breeding success. Mutualism, parasitism, it doesn't matter so much what the interactions are, they will happen. Something will be eating plants, and something else will be eating them. Then there's all the mico-organisms involved as well. The plant that produces an unpalatable compound will have advantage, as will the plant that spreads seed via grazing. One is parasitised, the other working in symbiosis unbeknownst to it's grazers. The plant with the grazing defense will now have to work out how to spread seed. The plant that uses other organisms for this will have advantage unless it is grazed to nothing. There is no plan for organisms to develop such things as fruit, but there is advantage to those who mutate and/or create any slight change that makes them fitter for survival.

 

Cooperation lends advantage. This is not a direction, or a plan either, it just is. Those with the best advantages have the upper hand. The entire thing is based on reproductive success. Even within solitary communities organisms have learned to work together ie: wolves, lions, ants, bees...

 

The community based organisms, whether eating each other or forming partnerships are obviously the more successful hence a planet full of interactive communities.

[HydrogenBond]

Maybe the problem has to do with the term evolution. The term evolution may be like the word "Microsoft" which is restricted to a given definition, with violation of this word subject to penalties.

 

It could be like the using the term Xerox to generically mean a photocopy machine. Some will understand what you mean. But since there are other companies besides Xerox that make those things, using the generic term Xerox ,can create confusion if it is really is a Toshiba copy machine.

 

Maybe I should not be concerned with the formal word "evolution" but with the observation of how eco-systems reach a symbiotic balance. We may not know what that balance may be until we investigate the system. But we do know a steady state balance will form. Life forms a circle of nature.

 

But in the same token, genetics can create random changes that can strengthen the circle or knock it out of balance. But eventually the eco-system finds a way to reform a new circle if needed. Maybe that is not evolution. Maybe we can come up with another term for this integration pattern in nature that has a sense of predictable direction.

[freeztar]

But in the same token, genetics can create random changes that can strengthen the circle or knock it out of balance. But eventually the eco-system finds a way to reform a new circle if needed. Maybe that is not evolution. Maybe we can come up with another term for this integration pattern in nature that has a sense of predictable direction.

 

It is called ecological succession and it leads to a climax community. When a climax community attains a normalized continuation, this would be called homeostasis (which is a term I'm sure you are familiar with through chemistry).

[CraigD]

Though I’m tardy to this discussion, and though the following claim is arguably a minor error among the several faith-based conclusions voiced in this thread, I think it’s dramatically wrong enough to compel me to contradict it:

Currently there are no warm blooded mammals on earth that could possibly grow to 70 tons, metabolizing tons of vegetation, especially in an already hot environment without quickly overheating itself to death.

The blue whale, believed to be the largest terrestrial animal to every exist, is a present day warm blooded mammal massing over 170 tons, much larger than any dinosaur. They metabolize at a tremendous rate – 73000 W average, about 1000 times human, while having about 300 times our surface (skin) area, yet don’t overheat and die.

 

Limiting factors on how large any land animal can be are the biomechanics of a musculoskeletal system capable of supporting their mass against gravity, factors avoided to a great extent by large aquatic animals such as whales.

[Moontanman]

Though I’m tardy to this discussion, and though the following claim is arguably a minor error among the several faith-based conclusions voiced in this thread, I think it’s dramatically wrong enough to compel me to contradict it:

 

The blue whale, believed to be the largest terrestrial animal to every exist, is a present day warm blooded mammal massing over 170 tons, much larger than any dinosaur. They metabolize at a tremendous rate – 73000 W average, about 1000 times human, while having about 300 times our surface (skin) area, yet don’t overheat and die.

 

Limiting factors on how large any land animal can be are the biomechanics of a musculoskeletal system capable of supporting their mass against gravity, factors avoided to a great extent by large aquatic animals such as whales.

 

Craig, while I agree that I see no reason why mammals could not evolve into huge dinosaur sized animals, and elephants are not the biggest land mammals ever, you have forgotten one variable. Water takes away heat quite a bit more effectively than air. Whales are always fighting against the cold water. That is why whales that tend to live in cold water also tend to be very big without over heating.

[CraigD]

I think it should also be noted that there did seem to be a lower size limit on dinosaurs. If i remember correctly there were no dinosaurs smaller than the size of a chicken (hmmm tastes like chicken!)

This intriguing IIRC surely got me to thinking and reading – thanks, MTM. :)

 

A typical small adult chicken masses 2-3 kg.

The smallest dinosaur fossil find is Anchiornis, estimated adult mass about 0.11 kg – about pigeon size.

The smallest known existant mammal is the Etruscan shrew, about 0.013 kg.

The smallest known bird is the bee hummingbird, about 0.018 kg.

The smallest fish is thought to be P progenetica, about 0.0025 kg

The smallest known insect is the male D. echmepterygis wasp, about 0.00005 kg.

 

From this, I suspect that the lower size limit on dinosaurs was likely around the same as for modern mammals, birds, and land-dwelling tetrapods in general. For a chordate to get much smaller than about 0.01 kg, something like a limbless aquatic body plan seems necessary, while to get another order of magnitude or a few smaller than that, the chordate body plan must be discarded altogether in favor of something with an exoskeleton. Another order of magnitude requires abandonment of much of a body plan at all to a lifeform consisting of just a single or a small collection of little-differentiated cells.

 

Because fossils preserved well enough to be recognized and reconstructed into an extinct animal happen rarely, especially for small species, I expect we may never find the dinosaur equivalent of a shrew, but based on the existence of roughly shrew-sized modern birds, I suspect they existed.

[Moontanman]

Did you see the worm snake in my post under the http://hypography.com/forums/biology/20957-convergent-evolution.html

 

thread? Worm shakes are so tiny, not sure how much they weigh but it can't be much!

[dduckwessel]

I have a theory that the larger dinosaurs (reptiles) grew as big because they began in 'water' and later adapted to land.

 

Even todays land animals cannot match the size of some aquatic creatures. Look at whales!

 

Take a goldfish for example. If I put it in a small tank, it will not grow larger than its environment. If however, it's put in a larger tank, it grows bigger and will keep doing so if transplanted to an even larger container.

 

My father-in-law had to put his pet goldfish into the nearby lake, it got so big (size of a trout when last seen).

[suppenkasper]

Before everything on earth used to be bigger...plants, trees, food so animals adapt to that I think

[Moontanman]

Before everything on earth used to be bigger...plants, trees, food so animals adapt to that I think

 

This is not true, there were small dinosaurs as well as large ones and redwood trees that are a live now are about as big as trees can get. Large dinosaurs tend to fossilize better than small ones, we also tend to glorify the large dinosaurs and give less attention to the small ones as well.

[Moontanman]

I have a theory that the larger dinosaurs (reptiles) grew as big because they began in 'water' and later adapted to land.

 

There were no aquatic dinosaurs.... none. All land vertebrates evolved from fish, even mammals via amphibians and reptiles.

 

Even todays land animals cannot match the size of some aquatic creatures. Look at whales!

 

Whales evolved from land animals, the water allowed them to grow enormous from small semi aquatic land animals.

 

Take a goldfish for example. If I put it in a small tank, it will not grow larger than its environment. If however, it's put in a larger tank, it grows bigger and will keep doing so if transplanted to an even larger container.

 

My father-in-law had to put his pet goldfish into the nearby lake, it got so big (size of a trout when last seen).

 

You have a dinosaur in a container? Your example is misleading, a confined gold fish stays small due to pheromones it gives off being concentrated in the water, if you keep a steady water flow through the container the gold fish would out grow a small container.

[dduckwessel]

 

You have a dinosaur in a container? Your example is misleading, a confined gold fish stays small due to pheromones it gives off being concentrated in the water, if you keep a steady water flow through the container the gold fish would out grow a small container.

 

Misleading? How? I stated what I saw! There was no steady water flow through the large aquarium but the gold fish outgrew it nevertheless.

 

 

 

For some reason I'm not being notified in some posts when there are replies!

[Moontanman]

Misleading? How? I stated what I saw! There was no steady water flow through the large aquarium but the gold fish outgrew it nevertheless.

 

 

 

For some reason I'm not being notified in some posts when there are replies!

 

I am somewhat of an expert when it comes to aquariums and aquarium kept fish,(48 years experience) a gold fish is stunted not by the size of it's environment but the concentration of pheromones it gives off. If you move it to a bigger aquarium the pheromones are diluted for some time so the fish grows bigger until the pheromones reach a certain level.

 

I have done experiments that show many fish are permanently stunted by these pheromones. I suspect so are gold fish but i have never done an experiment on gold fish so I will assume you have your information straight but your suggestion of the fish growing bigger when it is transfered to a larger tank does indeed correlate with my experiments on some fishes, gold fish are very adaptable but I would be surprised to find they would grow larger if transfered to a larger container but it is not impossible, I suggest it has to do with the age of the fish as well as the larger container. if you kept a gold fish in a small bowl for 10 years i doubt it would grow larger if transfered to a large container but a young fish might. But what does this have to do with dinosaurs?

[dduckwessel]

I am somewhat of an expert when it comes to aquariums and aquarium kept fish,(48 years experience) a gold fish is stunted not by the size of it's environment but the concentration of pheromones it gives off. If you move it to a bigger aquarium the pheromones are diluted for some time so the fish grows bigger until the pheromones reach a certain level.

 

I did not know it was due to pheromones.

 

your suggestion of the fish growing bigger when it is transfered to a larger tank does indeed correlate with my experiments on some fishes, gold fish are very adaptable but I would be surprised to find they would grow larger if transfered to a larger container but it is not impossible, I suggest it has to do with the age of the fish as well as the larger container. if you kept a gold fish in a small bowl for 10 years i doubt it would grow larger if transfered to a large container but a young fish might. But what does this have to do with dinosaurs?

 

If as you say a gold fish would keep growing when pheromones are diluted, then if you put a young gold fish into a lake, I wonder how big it would grow? Of course it would have to be an environment where there weren't any predators?

 

In answer to your question, "What does that have to with dinosaurs?" - well, dinosaurs were reptiles, right? Early reptiles came from water. If diluted pheromones (because of being in a larger volume of water) can cause a gold fish to grow bigger, could it have affected early reptiles the same way? Those same very large reptiles eventually crawled onto land and presto - dinosaurs.

[Moontanman]

I did not know it was due to pheromones.

 

 

 

If as you say a gold fish would keep growing when pheromones are diluted, then if you put a young gold fish into a lake, I wonder how big it would grow? Of course it would have to be an environment where there weren't any predators?

 

Gold fish have growth limits, the largest pure goldfish i have ever seen was about 12" long, I've heard of them getting as big as 18" but I have my doubts.

 

In answer to your question, "What does that have to with dinosaurs?" - well, dinosaurs were reptiles, right?

 

Not really, dinosaurs were dinosaurs, they parted from the reptile linage at about the same time mammals did.

 

Early reptiles came from water. If diluted pheromones (because of being in a larger volume of water) can cause a gold fish to grow bigger, could it have affected early reptiles the same way? Those same very large reptiles eventually crawled onto land and presto - dinosaurs.

 

Early reptiles evolved from amphibians which evolved from fishes, both mammals and dinosaurs evolved from reptiles. Reptiles did not evolve in the water and crawl out on land...

[dduckwessel]

both mammals and dinosaurs evolved from reptiles.

 

Is it known when reptiles split (mammals and dinosaurs) and the reason why?