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Author Topic: Why didn't insects become as big as dinosaurs?  (Read 16773 times)

Offline iko

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Why didn't insects become as big as dinosaurs?
« on: 06/02/2008 21:22:38 »
           

Why little insects couldn't manage to become as big as dinosaurs and dominate this Planet?
What didn't work in the perfect mechanism of spontaneous mutation, natural selection and evolution?

ikoD   [8D]
« Last Edit: 07/06/2008 12:59:24 by chris »


 

Offline Carol-A

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Re: Why didn't insects become as big as dinosaurs?
« Reply #1 on: 07/02/2008 07:37:25 »
The size of insects is limited by the system they have for getting oxygen to their bodies... a system of tubes running through them. The weight of these limits how big insects can grow. The larger beetles tend to be rather slow because of this. Back in the carboniferous, when Oxygen levels rose to perhaps as much as 35%, there were much larger insects.... 60cm dragonflies etc, but as the % of oxygen fell, so did the size of the insects
 

Offline DoctorBeaver

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Re: Why didn't insects become as big as dinosaurs?
« Reply #2 on: 07/02/2008 08:01:44 »
Carol - is that why insects in the tropical forests tend to be larger?
 

Offline iko

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Re: Why didn't insects become as big as dinosaurs?
« Reply #3 on: 07/02/2008 19:10:18 »
The size of insects is limited by the system they have for getting oxygen to their bodies... a system of tubes running through them. The weight of these limits how big insects can grow. The larger beetles tend to be rather slow because of this. Back in the carboniferous, when Oxygen levels rose to perhaps as much as 35%, there were much larger insects.... 60cm dragonflies etc, but as the % of oxygen fell, so did the size of the insects

Hi Carol-A,

I knew another story, concerning different types of skeleton...

whykoD   ;)
« Last Edit: 08/02/2008 22:34:59 by iko »
 

Offline Carol-A

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Re: Why didn't insects become as big as dinosaurs?
« Reply #4 on: 08/02/2008 10:08:42 »
I suspect that the temperature in the tropical rainforest is why they have more types of insects!
 

Offline iko

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Re: Why didn't insects become as big as dinosaurs?
« Reply #5 on: 08/02/2008 18:36:40 »
EXOskeleton is the mainframe for insects.
we have ENDOskeleton that makes everything
easier when it comes to growing up...



Quote
...
Ecdysis
 
A spider undergoes moulting
Time series photos of a Tibicen Dog Day Cicada moulting in Ohio USA.The relative rigidity of the exoskeleton means that continuous growth of arthropods is not possible. Therefore, growth is periodic and concentrated into a period of time when the exoskeleton is shed, called moulting or ecdysis, which is under the control of a hormone called ecdysone. Moulting is a complex process that is invariably dangerous for the arthropod involved. Before the old exoskeleton is shed, the cuticle separates from the epidermis through a process called apolysis. New cuticle is excreted by the underlying epidermis, and mineral salts are usually withdrawn from the old cuticle for re-use. After the old cuticle is shed, the arthropod typically pumps up its body (for example, by air or water intake) to allow the new cuticle to expand to a larger size: the process of hardening by dehydration of the cuticle then takes place. Newly molted arthropods typically appear pale or white, and darken as the cuticle hardens.
....
from Wikipedia:  http://en.wikipedia.org/wiki/Exoskeleton
« Last Edit: 08/02/2008 18:40:21 by iko »
 

Offline iko

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Re: Why didn't insects become as big as dinosaurs?
« Reply #6 on: 09/02/2008 22:54:02 »
Fishing through the net, you get thousands of bits and pieces, as usual:


Quote
...
Larva Stage

Why does a Manduca larva undergo five molts?

Insects have their skeleton on the outside, this is called an exoskeleton. Exoskeletons make growing bigger difficult. Manduca weighs about 1 milligram when is hatched and about 10 grams just before pupation. To grow that much, the insect is doing some pretty amazing things with it's exoskeleton.

There is a limit to how much the insect can grow. Because of the growth limits Manduca must shed it's exoskeleton often.
The process of shedding the old skin while building a new, bigger one underneath is called, molting.

During molting, the insect usually is usually quiescent (doesn't eat) for many hours to allow a new exoskeleton to develop. After molting, the mandibles are hardened and the insect eats the old shed exoskeleton except the very hardened hood capsule. Once the mandibles are hardened, the insect eats the shed exoskeleton except for the very hardened head capsule
...


« Last Edit: 10/02/2008 22:26:43 by iko »
 

Offline Carol-A

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Re: Why didn't insects become as big as dinosaurs?
« Reply #7 on: 11/02/2008 07:38:01 »
http://www.saburchill.com/chapters/chap0021.html

This is quite a good link about the way insects get oxygen around their bodies!
 

Offline JimBob

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Re: Why didn't insects become as big as dinosaurs?
« Reply #8 on: 16/02/2008 18:32:40 »
Yet there is also a size limitation placed on an exoskelatal-based creature. Due to the laws of physics, the legs become unable to support growth above a certain size as growth only occurs during the molting period. Thus the muscles must be strong enough for the animal to be able to move after moulting to the larger size and thus survive.
 

Offline iko

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Re: Why didn't insects become as big as dinosaurs?
« Reply #9 on: 17/02/2008 22:07:57 »
Thanks JimBob,

this is the reason I was told, ages ago.
You explained it in a proper way.

ikoD
 

Offline JimBob

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Re: Why didn't insects become as big as dinosaurs?
« Reply #10 on: 18/02/2008 00:24:04 »
Iko,

Just remember that Carol is correct about the oxygen part as well.
 

Offline iko

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Re: Why didn't insects become as big as dinosaurs?
« Reply #11 on: 19/02/2008 14:23:07 »
I remember, JimBob

but don't you think that the oxygen distribution system could have been optimized over million years, through mutations and natural selection, evolving into improved performance?
On the other hand, nothing can be done if your bones are sort of 'external' to the body and they have to mealt and solidify later, on a grown up soft and jelly body (ready to be eaten up!).
At a certain volume, this is just physically impossible, much before a dinosaur-size!
Cheers,

ikoD  [^]


« Last Edit: 19/02/2008 15:56:53 by iko »
 

Offline TheHerbaholic

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Re: Why didn't insects become as big as dinosaurs?
« Reply #12 on: 13/05/2008 08:29:03 »
When the air was alot more oxygenated back millions of years ago, their was spiders the size of house cats. And millipeeds that where as long as buses! I seen this on MegaBeasts or something like that on discovery or nat geo.
 

blakestyger

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Re: Why didn't insects become as big as dinosaurs?
« Reply #13 on: 14/05/2008 09:16:42 »
Megarachne, a 300 million year old fossil from the Carboniferous of Argentina was described in 1980 at the world's largest spider; it had a body length of 35cm and leg span of 50cm and can be seen in the Sedgewick Museum, Cambridge.

There is no reason why the circulation of oxygen in insects should improve with evolution as it is essentially a 'blind' process with neither an agenda nor, as the Victorians believed, a natural progression from the primitive to the advanced.
 

Offline Supercryptid

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Re: Why didn't insects become as big as dinosaurs?
« Reply #14 on: 15/05/2008 11:53:20 »
Megarachne, a 300 million year old fossil from the Carboniferous of Argentina was described in 1980 at the world's largest spider; it had a body length of 35cm and leg span of 50cm and can be seen in the Sedgewick Museum, Cambridge.
It has been determined more recently that Megarachne was in fact a type of sea scorpion, not a spider. That means that the largest confirmed spider ever is the Goliath Bird-eater or some other tarantula species. There are, however, a couple of questionable reports in the cryptozoological circle that concern giant spiders. I believe there was a report of a spider in the Congo that was the size of a "pygmy" (I guess something like a 4-foot leg-span). There was also another report (I think in Australia) of a dog-sized spider.
 

blakestyger

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Re: Why didn't insects become as big as dinosaurs?
« Reply #15 on: 15/05/2008 17:58:30 »
That is interesting Supercrypted, as it really does look like a spider, with all the spidery proportions and hairs and everything - I'm amazed to hear this. Do you know what the basis for this reassignment is? It's not likely to be DNA - I'd be interested to know.
 

Offline Supercryptid

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Re: Why didn't insects become as big as dinosaurs?
« Reply #16 on: 16/05/2008 02:23:45 »
Quote
That is interesting Supercrypted, as it really does look like a spider, with all the spidery proportions and hairs and everything - I'm amazed to hear this. Do you know what the basis for this reassignment is? It's not likely to be DNA - I'd be interested to know.

No, it wasn't DNA. I think it was morphology. Here are some links about it:

http://www.sedgwickmuseum.org/about/news/05spider.html
http://homepage.mac.com/paulselden/Sites/Website/Megarachne.pdf
 

blakestyger

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Re: Why didn't insects become as big as dinosaurs?
« Reply #17 on: 16/05/2008 11:46:46 »
Thanks, you're right. I'll have to look more closely next time I see it- which will be quite soon as I live within 45 mins of it.
 

Offline iko

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Re: Why didn't insects become as big as dinosaurs?
« Reply #18 on: 07/06/2008 10:44:04 »
Megarachne, a 300 million year old fossil from the Carboniferous of Argentina was described in 1980 at the world's largest spider; it had a body length of 35cm and leg span of 50cm and can be seen in the Sedgewick Museum, Cambridge.
It has been determined more recently that Megarachne was in fact a type of sea scorpion, not a spider. That means that the largest confirmed spider ever is the Goliath Bird-eater or some other tarantula species. There are, however, a couple of questionable reports in the cryptozoological circle that concern giant spiders. I believe there was a report of a spider in the Congo that was the size of a "pygmy" (I guess something like a 4-foot leg-span). There was also another report (I think in Australia) of a dog-sized spider.

Right, friendos;

speaking of skeletons, a sea scorpion should have less problems of gravity and jelly-body collapse!

ikoD  [^]
« Last Edit: 07/06/2008 10:46:22 by iko »
 

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Re: Why didn't insects become as big as dinosaurs?
« Reply #18 on: 07/06/2008 10:44:04 »

 

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