Evolution
Why aren't insects generally bigger in size?
Not that we're complaining about it, especially after looking at the
picture, but simply wondering why don't insects and other arthropods
reach bigger sizes. Turns out that scientists are still pondering over
the same question too, and all we now have are hypotheses, said insect
physiologist Jon Harrison, at Arizona State University in Tempe. (Source
1
)
The first hypothesis stems
from the fact that larger arthropods don't have thicker exoskeletons,
thereby discouraging larger sizes.
Another hypothesis suggests that being larger makes you a more attractive meal.
Insects also have open circulatory systems, where blood and bodily
fluids aren't bound up in vessels, making it more difficult to move
blood throughout a large body, as circulation would be hampered by
gravity, which pulls blood downward.
But the most plausible
hypothesis has to do with the way most insects breathe. Insects
"breathe" via tiny tubes called trachea, which passively transport
oxygen from the atmosphere to bodily cells. Once insects reach a certain
size, the theory goes, the insect will require more oxygen than can be
shuttled through its trachea. (Source 1) And this hypothesis is
supported by the fact that ancient insects were indeed much larger- 300
million years ago, there were dragonflies the size of hawks, with
wingspans of about 6 feet (1.8 meters), and ants the size of
hummingbirds. In those times, the oxygen content in the atmosphere was
about 35 percent, versus 21 percent today.
Also, many species
of insects that were raised in atmospheres with oxygen levels lower than
modern Earth's they grew to be smaller than those reared in modern
atmosphere. And the dragonflies and many of the other insects raised in
higher oxygen matured more quickly and became larger adults. (Source 2)
But more research needs to be done to support any of these hypotheses
and more evidence needs to be dug out. Of course, it's all fun and games
and cool research until they start chasing you down (kiddin!) :)
Source:
1) http://www.livescience.com/
2) http://io9.com/giant-bugs/
Image: http://io9.com/giant-bugs/
Why aren't insects generally bigger in size?
Not that we're complaining about it, especially after looking at the picture, but simply wondering why don't insects and other arthropods reach bigger sizes. Turns out that scientists are still pondering over the same question too, and all we now have are hypotheses, said insect physiologist Jon Harrison, at Arizona State University in Tempe. (Source 1
Not that we're complaining about it, especially after looking at the picture, but simply wondering why don't insects and other arthropods reach bigger sizes. Turns out that scientists are still pondering over the same question too, and all we now have are hypotheses, said insect physiologist Jon Harrison, at Arizona State University in Tempe. (Source 1
)
The first hypothesis stems from the fact that larger arthropods don't have thicker exoskeletons, thereby discouraging larger sizes.
Another hypothesis suggests that being larger makes you a more attractive meal.
Insects also have open circulatory systems, where blood and bodily fluids aren't bound up in vessels, making it more difficult to move blood throughout a large body, as circulation would be hampered by gravity, which pulls blood downward.
But the most plausible hypothesis has to do with the way most insects breathe. Insects "breathe" via tiny tubes called trachea, which passively transport oxygen from the atmosphere to bodily cells. Once insects reach a certain size, the theory goes, the insect will require more oxygen than can be shuttled through its trachea. (Source 1) And this hypothesis is supported by the fact that ancient insects were indeed much larger- 300 million years ago, there were dragonflies the size of hawks, with wingspans of about 6 feet (1.8 meters), and ants the size of hummingbirds. In those times, the oxygen content in the atmosphere was about 35 percent, versus 21 percent today.
Also, many species of insects that were raised in atmospheres with oxygen levels lower than modern Earth's they grew to be smaller than those reared in modern atmosphere. And the dragonflies and many of the other insects raised in higher oxygen matured more quickly and became larger adults. (Source 2)
But more research needs to be done to support any of these hypotheses and more evidence needs to be dug out. Of course, it's all fun and games and cool research until they start chasing you down (kiddin!) :)
Source:
1) http://www.livescience.com/
2) http://io9.com/giant-bugs/
Image: http://io9.com/giant-bugs/
The first hypothesis stems from the fact that larger arthropods don't have thicker exoskeletons, thereby discouraging larger sizes.
Another hypothesis suggests that being larger makes you a more attractive meal.
Insects also have open circulatory systems, where blood and bodily fluids aren't bound up in vessels, making it more difficult to move blood throughout a large body, as circulation would be hampered by gravity, which pulls blood downward.
But the most plausible hypothesis has to do with the way most insects breathe. Insects "breathe" via tiny tubes called trachea, which passively transport oxygen from the atmosphere to bodily cells. Once insects reach a certain size, the theory goes, the insect will require more oxygen than can be shuttled through its trachea. (Source 1) And this hypothesis is supported by the fact that ancient insects were indeed much larger- 300 million years ago, there were dragonflies the size of hawks, with wingspans of about 6 feet (1.8 meters), and ants the size of hummingbirds. In those times, the oxygen content in the atmosphere was about 35 percent, versus 21 percent today.
Also, many species of insects that were raised in atmospheres with oxygen levels lower than modern Earth's they grew to be smaller than those reared in modern atmosphere. And the dragonflies and many of the other insects raised in higher oxygen matured more quickly and became larger adults. (Source 2)
But more research needs to be done to support any of these hypotheses and more evidence needs to be dug out. Of course, it's all fun and games and cool research until they start chasing you down (kiddin!) :)
Source:
1) http://www.livescience.com/
2) http://io9.com/giant-bugs/
Image: http://io9.com/giant-bugs/
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