Posted on 07/17/2012 2:44:00 PM PDT by SunkenCiv
Around 300 million years ago, dragonflies with the wingspans of hawks flitted above coal-producing swamps. Such giants don't exist today, partly because oxygen levels in the atmosphere are much lower. But another reason is that the evolution of birds and their increasing agility in the air forced flying insects to shrink, according to a new study.
Like all multicellular animals, insects fuel their metabolism by taking in oxygen. Unlike creatures with lungs, however, insects draw in air through holes in their shell-like exoskeletons. The oxygen diffuses from those holes to the creatures' tissues through a dense network of tubes. Because diffusion becomes less efficient as the tubes get longer, the atmospheric concentration of oxygen is a powerful constraint on body size, especially for active insects that fly. The higher the concentration, the larger the insects can grow...
Several previous studies, especially those in the past 5 years, have hinted that factors other than oxygen levels influenced insect size.
For their new study, paleontologists Matthew Clapham and Jered Karr of the University of California, Santa Cruz, sorted more than 10,500 fossils of flying insects that lived in the past 320 million years into 10-million-year intervals. In each interval, they compared the largest wing length, which presumably belonged to the largest insect that lived during that particular period, to the average oxygen concentration in Earth's atmosphere during that time.
Results of the study, which the researchers report online today in the Proceedings of the National Academy of Sciences, show that for the first 170 million years or so of flying-insect evolution, wing length grew and shrank in step with variations in average oxygen concentration. Then, between 140 million and 130 million years ago, wing length dropped even though oxygen levels began to rise.
(Excerpt) Read more at news.sciencemag.org ...
Big old cousin. Large flying insects that lived before birds evolved, such as the 300-million-year old Stephanotypus schneideri (main image),were typically much larger than those that evolved afterward, including the 12-million-year old Epiaeschna lucida (top left, shown to same scale). Credit: (Stephanotypus) Wolfgang Zessin
Giant Bugs a Thing of the Past, Study Suggests
National Geographic News | November 21, 2007 | Hope Hamashige
Posted on 11/22/2007 8:27:40 AM PST by ricks_place
http://www.freerepublic.com/focus/news/1929315/posts
sidebars from there:
Scientists find fossil of enormous bug
AP via YAHOO! | 11-20-07 | Thomas Wagner
Posted on 11/20/2007 10:45:12 PM EST by Pharmboy
http://www.freerepublic.com/focus/news/1928675/posts
Scientists Uncover Fossil of Biggest Bug Ever at 8 Feet Long
Fox News | 11-21-07
Posted on 11/21/2007 1:36:51 PM EST by Renfield
http://www.freerepublic.com/focus/chat/1928960/posts
390-million-year-old scorpion fossil — biggest bug known
Eurekalert! | 11/21/07 | Janet Rettig Emanuel
Posted on 11/21/2007 5:29:48 PM EST by Teflonic
http://www.freerepublic.com/focus/chat/1929079/posts
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| GGG managers are SunkenCiv, StayAt HomeMother & Ernest_at_the_Beach | |
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Imagine the amount of Off you'd go through in a year. |
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I personally think falling oxygen levels was the primary driver of shrinking insects. I know that considerably larger insects have been grown in labs.
Its the summer of the dragonflies here in southern Michigan. Hot and dry with dragonflies of all kinds everywhere.
Pterodactyl ate 'em.
Reminds me of a song, “Where have all the man-eating flowers gone...”
/johnny
Bush killed them.
It’s too bad there’s so much evo BS in the article......
Maybe rhino-sized bearded dragons ate them.
Not just falling levels of O2, but falling atmospheric pressure as well. That’s why no land animal will ever reach anything near the size of a brachiosaur again. The higher atmospheric pressure in the past created more buoyancy, offsetting gravity to an extent.
It would be great to be able to go back to
those days and walk around looking at these
creatures...as long as I have a force-field
generator turned on
Considering the fact that the article is about evolution it shouldn’t be a real shocker.
They became Democrats and migrated to Washington DC to suck the life blood out of the nation.
The pressure would also make it easier to force oxygen into the blood streams.
“Where Have the Hawk-Sized Insects Gone?”
Houston.
Canada.
Maybe the earth’s gravity has changed.
This is extremely cool.
Man made global warming got them.
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