According to research, during the Carboniferous and Permian, insects were incredibly big. Thanks to fossils that were found by archaeologists, now we know that there once existed gigantic insects. There are several hypotheses as to why they shrunk over time and now are so tiny that some are barely noticeable. One of the most valid or credible hypotheses is that in the past there was more oxygen, and that since the level or quantity of oxygen has decreased this caused insects to decrease in size as well. Three hundred million years ago, giant bugs were normal and this was due to an atmosphere with 30 percent more oxygen than we have today. Nowadays our oxygen level is around twenty percent. An article by Ker Than for the National Geographic News states that birds are the reason why gigantic insects may have become extinct. (1) (1) "The largest insects today could perhaps be three times as large as they currently are, based on current oxygen levels”. During the Jurassic Era birds became larger and this caused a threat to giant insects, which quickly might have become their prey. Yet, this is just a theory that has not been proven. It is most likely that there size decreased due to the oxygen level going down significantly. (2) “We know that these gigantic forms went extinct as oxygen levels declined drastically in the Permian (Huey & Ward, 2005), and some gigantic forms re-evolved in the Cretaceous oxygen peak (Dudley, 2000).”.
It would be quite terrifying if gigantic insects would still roam the earth, luckily for us that is no longer the case. The end for giant insects came with the evolution of birds and oxygen changes. Giant insects ruled the sky about 150 million years ago, then came the birds. (University of California, Santa Cruz). The enduring theory about the existence of giant insects is that there is relationship between the amount of oxygen in the atmosphere and the size of insects. During the Permian period the Earth’s atmosphere had more than 30 percent of the oxygen, compared to the 20 percent of today. This vital gas is what sets a limit on the size of animals, the “seething quantities” of the eras in the past allowed flying insects to have larger bodies and faster metabolisms.(Discover Magazine) Matthew Clapham and Jarred Karr have found evidence to support the idea after analyzing more than 10,500 fossilized insects wings. The research showed that the biggest wingspans of flying insects where a record of the oxygen in the atmosphere for their initial 150 million years of evolution. Since the gas level reached its peak during the Permian period that is the time when the largest insects lived, as the levels decreased so did the insects’ size(PNAAS). The pattern stopped though, when the oxygen concentrations rose in the Cretaceous period and the insects didn’t grow in size. This is due to the fact that feathered flying dinosaurs, birds, where beginning to take over the skies. The size of insects didn’t increase because being smaller was an advantage to escape from birds. The smaller insects were able to maneuver out of the bird’s reach with greater facility, that is why Clapham and Kerr believe that birds exerted a “size-selective pressure” on the insects. Since the birds ate the bigger insects only the smaller ones survived which kept the group as a whole from increasing in size. It is not clear whether or not it was the decrease in oxygen or the evolution of flying reptiles(pterosaurs) during the Jurassic period what caused the insects to become smaller. The combined factor of birds in the sky and a lower percentage of oxygen in the atmosphere is what thankfully keeps the insects small in size.
sources: http://phys.org/news/2012-06-giant-insects-evolution-birds.html university of California, Santa Cruz http://blogs.discovermagazine.com/notrocketscience/2012/06/04/giant-insects-disappeared-thanks-to-falling-oxygen-levels-and-agile-birds/#.Upom0mRDs8M Discover Magazine
http://www.pnas.org/content/early/2012/05/25/1204026109 Proceedings of the National Academy of Sciences of the United States of America
Insects are small Arthropods in the class of insecta. (Online dictionary.com) The fact is that not all insets where small, in fact the well-known American cockroach’s Pre-historic ancestor the Blattoptera has been recorded to be six inches or longer. (National Geographic) The prehistoric that where so large became so large do to some advantages; they could ingest larger prey, and could defend themselves from a wider variety of predators. Also some reports state that the larger size of their bodies insolated heat more than a smaller one, enabling the body to withstand hotter tempetures. The larger body was due to the large availability of food. This cased the carnivores of the prehistoric-ages to become larger over time, to be able to consume the larger insects. (Nina Rastogi) There are no longer giant insects in the same scale that there once was. This is because planet cooled down during the ice age. To survive the ice age insects had to evolve and a smaller animal was more suitable to the new environment. The smaller animal was able to reproduce more and quickly because it took less time for the body to grow until its full-grown size. (Jack L. Conrad )Also the animals had to escape from the larger population of mammals arising and they could do this by shrinking because the predator could not see the insect and he insect could protect itself in smaller areas, which the larger predator could not enter.( ROBERT T. GONZALEZ ) • Why do we no longer have giant insect or why haven’t they grown back? According to American Physiological Society, the earth’s oxygen concentration is not as high as it was in the prehistoric age. The cockroach needs a larger concentration of oxygen to become larger and with global warming many species not just insects are becoming smaller do to this phenomena. (Jennifer A. Sheridan & David Bickford)
http://phys.org/news79804314.html(American Physiological Society) http://www.thefreedictionary.com/insect http://www.slate.com/articles/news_and_politics/explainer/2009/02/a_snake_the_size_of_a_plane.html (Nina Rastogi) http://www.nature.com/nclimate/journal/v1/n8/full/nclimate1259.html(Jennifer A. Sheridan & David Bickford) http://io9.com/5850741/climate-change-is-causing-earths-animals-to-shrink (ROBERT T. GONZALEZ ) http://news.nationalgeographic.com/news/2001/11/1112_TVbigroach.html
During the Permian era insects were huge compared to today’s proportions, boasting wingspans up to 30 inches across. There are different reasons why these prehistoric insects were so big. The cause was mostly due to the high levels of oxygen which helped fuel insect growth [Jennifer Welsh, 2012]. As more evidence of oxygen’s role emerged, we know these gigantic forms were extinct as oxygen levels declined drastically in that Permian era (Huey & Ward, 2005). [Bioteaching, 2012] Birds played an important role within larger insects’ evolution. Such gigantic specimens were common 300 million years ago, but fortunately did not survive to pester us today. The evolution of birds from dinosaurs caused smaller insects to survive as they were more manoeuvrable to escape [Thomas H. Maugh, 2012] . Researchers noticed the decreasing pressure in oxygen happened around the same time birds first took to the skies. About 150 million years ago, the “first bird” Archaeopteryx appeared, and about 25 million years later, the lineage had diversified greatly, meaning birds could fly and eat the huge insects [Jennifer Welsh, 2012]! In conclusion, insects are no longer 6-12 inches long because oxygen levels declined and natural selection occurred. Insects needed more oxygen to grow larger. Also bigger insects were eaten up by birds. Only the smallest insects could survive by escaping the detection of predators. References Maugh , Thomas. "Los Angeles Times." Bird's evolution led to disappearance of giant insects, study finds. N.p., 24 Jun 2012. Web http://articles.latimes.com/2012/jun/04/science/la-sci-sn-insects-birds-20120604
Welsh , Jennifer. "Why Giagantic Insects Shrunck to Modern Size." Predation and Competition. Live science beta, 4 Jun 2012. Web. http://m.livescience.com/20735-giant-insects-shrunk.html
"Teaching Biology ." Gigantism in Insects. N.p., 4 Mar 2012. Web. http://bioteaching.wordpress.com/2012/03/24/gigantism-in-insects/
There are many theory's revolving around the fact that insects, in prehistoric times we much bigger than they are now. The biggest theory is: the temperature size rule, stating that species in colder habitats tend to be bigger due to heat regulation. Another theory is that before in pre-historic times there was a lot more oxygen,when the oxygen levels started decreasing, so did the insects. Other theory's include that there exo-skeletons were not able to be stable when they were so big.Incredbly enough the giant insects would have a much easyer time to get Around since the air was much denser. Insects breath through thier tracias, the tracial system Works by diffusion, the mechanism of diffusion is that the bigger the mass, the less surface área meaning that it is less ifficiant. The oxygen theory has been views as the most valid and logical. sorce:http://rspb.royalsocietypublishing.org/content/early/2010/03/04/rspb.2010.0001.full
Many things are involved in the size of insects. The first one is the temperature-size rule. This tells us species in cold environments tend to be bigger than ones in hot ones(1) . Another rule is the island rule. This one states that small animals isolated on mediterranean islands become bigger over time. It also says big animals become smaller (1). Back in the Permian era, insects were giant because there was more oxygen in the atmosphere. This animals had enough biomass to support them for flight. The climate was more tropical and this helped the insects grow more. The amount of oxygen on the planet affects directly the size of insects (1), studies have shown this as well. Other hypothesis say that insects are small because their respiratory system limits their growth (2). This is an unfavorable surface area to volume ratio. Another part that limits insects further grow is their exoskeleton. An exoskeleton limits their growth through molting. Something we know for sure, insects were bigger before. This is confirmed by the fossil record (1 and 2). To conclude I can say insects have many limitations on todays earth for their growth. For starters, their exoskeletons molting and the oxygen levels on earth today. Also, their respiratory system and climate add to why they are so small (2). I would expect that millions of years from now insects will be even smaller than they are today.
1) Gigantism in Insects, 2012, Teaching Biology. http://bioteaching.wordpress.com/2012/03/24/gigantism-in-insects/
2) A sizeable advantage, Why are insects so small? 2013, http://amisstome.wordpress.com/2013/03/25/a-sizeable-advantage-why-insects-are-so-small/
Giant insects lived millions of years ago in the Carboniferous and early Permian Periods, but why are they not alive today and buzzing around the world causing chaos? Scientists have two reasons to why these creatures are not with us anymore. (Emily Howard, May 07, 2013) First off and what seems to be a big contributor in the extinction and evolution of these giants, is of how the earth’s atmosphere has changed. During the Carboniferous Period, the planet was warmer, moister and contained more oxygen. The oxygen level during that period was about 30 percent of the air while today’s air only contains about 21 percent. Oxygen is important for insects because no insect has lungs; they rely on air flowing through a series of openings throughout their body which connect directly to tissues that need oxygen. (Emily Howard, May 07, 2013) The second contributor in the extinction and evolution of these was the evolution of birds. As the first bird appeared on earth, they evolved to be faster and more agile than the giant insect. The birds could catch and eat the insects more and more causing the insects to go extinct or have to evolve to be smaller, faster and more agile to keep away from birds. (Emily Howard, May 07, 2013) One example of a giant insect is the Meganeura. The Meganeura lived during the Carboniferous Period and is very similar to dragonflies today. It looked and acted like a dragonfly but it was about 10 times the size of a dragonfly. The Meganeura was classified as a griffinfly and had a wingspan that could reach up and over 75 cm. They are classified as griffinflies and not dragonflies due to morphological differences between the two. The higher amounts of oxygen during that period would supply a passive boost to the tissues which allowed insects to grow larger. As the oxygen levels decreased, insects would not be able to keep their large size causing them to evolve into smaller forms or to go extinct. The Meganeura is one of the largest known insect to ever exist. (http://www.prehistoric-wildlife.com/species/m/meganeura.html) Another example of these incredibly large insects is the Arthropleura, a contender for the biggest arthropod of all time. It is related to centipedes and millipedes and has a crustacean ancestry as well. It, too, also lived during the Carboniferous period and into the Permian period. The dying oxygen levels had its toll on these gigantic creatures. The lack of vegetation did not just affect it because of the oxygen levels but it also caused there to be less moisture in the air. The crustacean part of this giant was dried out without the moisture causing the species to go extinct.
Unlike humans, insects take in atmospheric oxygen through spiracles, opening in the cuticle through which gases enter and exit the body, so the oxygen travel via the tracheal system, the insect’s respiratory system, and inside the tracheal system each tracheal tube ends with a tracheole, where the oxygen dissolves into the tracheole fluid; finally, oxygen then diffuses into the cells. Back then in the Carboniferous and Permian periods, atmospheric oxygen concentrations were definitely significantly higher that they are today. Prehistoric insects breathed air that was 31-35% oxygen, unlike nowadays insects, which only have about 21% of oxygen in the air to breathe in. When the oxygen levels are higher, like in the Carboniferous and Permian periods, the tracheal system of insects can supply sufficient oxygen to meet the metabolic needs of a larger insect. Oxygen can reach cells deep within the insect’s body, no matter how long a insect measures, making atmospheric oxygen the most limiting factor on insect size.
Lloyd, Robin. "Why Bugs Are Not Huge." Live Science. N.p., 13 Aug 2007. Web. .
Guilfoy, Christine . "Giant insects might reign if only there was more oxygen in the air." . N.p., 11 Oct 2006. Web. .
"Why are there no really big insects any more? Blame birds.." the ranger's blog. N.p., 09 Jun 2012. Web. .
Insects have gotten smaller over time because back millions of years ago animals would try to get food (this is animals that were carnivores that would feast on other insects). This made insects become vulnerable when they were too big so because of this insects' genes throughout time would become more dominant the smaller they were. As time passed so did most insects become smaller. Firefles, for example, are an insect that got smaller because if they flew as large insects the birds would probably catch them, so they became smaller and more aerodynamic.
There are lots of theories that explain why insects are not 6-12 inches. One theory is that insects' exoskeletons may not be strong enough to allow them to get much bigger. So they can become bigger there exoskeleton has to impossibly thick. Because exoskeletons are rigid, insects need to molt as they grow, shedding the old skin and growing a new one. Larger animals, particularly those without protective skeletons, would make for more attractive meals to a predator. Another theory suggests being larger makes you a more attractive meal, whether molting or not. A study found that the size of past flies decreased as birds evolved telling us that smaller creatures were better able to avoid hungry raptors and pass on their genes. Another theory says that insects breathe through tiny tubes called trachea, that transports oxygen from the atmosphere to the cells in the body cells. Once insects reach a certain size, the theory says, the insect will need more oxygen than can be shuttled through its trachea. http://www.livescience.com/24122-why-insects-are-not-bigger.html http://bioteaching.wordpress.com/2012/03/24/gigantism-in-insects/
According to research, during the Carboniferous and Permian, insects were incredibly big. Thanks to fossils that were found by archaeologists, now we know that there once existed gigantic insects. There are several hypotheses as to why they shrunk over time and now are so tiny that some are barely noticeable. One of the most valid or credible hypotheses is that in the past there was more oxygen, and that since the level or quantity of oxygen has decreased this caused insects to decrease in size as well. Three hundred million years ago, giant bugs were normal and this was due to an atmosphere with 30 percent more oxygen than we have today. Nowadays our oxygen level is around twenty percent. An article by Ker Than for the National Geographic News states that birds are the reason why gigantic insects may have become extinct. (1) (1) "The largest insects today could perhaps be three times as large as they currently are, based on current oxygen levels”. During the Jurassic Era birds became larger and this caused a threat to giant insects, which quickly might have become their prey. Yet, this is just a theory that has not been proven. It is most likely that there size decreased due to the oxygen level going down significantly. (2) “We know that these gigantic forms went extinct as oxygen levels declined drastically in the Permian (Huey & Ward, 2005), and some gigantic forms re-evolved in the Cretaceous oxygen peak (Dudley, 2000).”.
ReplyDelete(1) http://news.nationalgeographic.com/news/2012/06/120601-insects-birds-giant-prehistoric-clapham-proceedings-science-bugs/
(2) http://bioteaching.wordpress.com/2012/03/24/gigantism-in-insects/
ReplyDeleteIt would be quite terrifying if gigantic insects would still roam the earth, luckily for us that is no longer the case. The end for giant insects came with the evolution of birds and oxygen changes. Giant insects ruled the sky about 150 million years ago, then came the birds. (University of California, Santa Cruz). The enduring theory about the existence of giant insects is that there is relationship between the amount of oxygen in the atmosphere and the size of insects. During the Permian period the Earth’s atmosphere had more than 30 percent of the oxygen, compared to the 20 percent of today. This vital gas is what sets a limit on the size of animals, the “seething quantities” of the eras in the past allowed flying insects to have larger bodies and faster metabolisms.(Discover Magazine) Matthew Clapham and Jarred Karr have found evidence to support the idea after analyzing more than 10,500 fossilized insects wings. The research showed that the biggest wingspans of flying insects where a record of the oxygen in the atmosphere for their initial 150 million years of evolution. Since the gas level reached its peak during the Permian period that is the time when the largest insects lived, as the levels decreased so did the insects’ size(PNAAS). The pattern stopped though, when the oxygen concentrations rose in the Cretaceous period and the insects didn’t grow in size. This is due to the fact that feathered flying dinosaurs, birds, where beginning to take over the skies. The size of insects didn’t increase because being smaller was an advantage to escape from birds. The smaller insects were able to maneuver out of the bird’s reach with greater facility, that is why Clapham and Kerr believe that birds exerted a “size-selective pressure” on the insects. Since the birds ate the bigger insects only the smaller ones survived which kept the group as a whole from increasing in size. It is not clear whether or not it was the decrease in oxygen or the evolution of flying reptiles(pterosaurs) during the Jurassic period what caused the insects to become smaller. The combined factor of birds in the sky and a lower percentage of oxygen in the atmosphere is what thankfully keeps the insects small in size.
sources:
http://phys.org/news/2012-06-giant-insects-evolution-birds.html university of California, Santa Cruz
http://blogs.discovermagazine.com/notrocketscience/2012/06/04/giant-insects-disappeared-thanks-to-falling-oxygen-levels-and-agile-birds/#.Upom0mRDs8M Discover Magazine
http://www.pnas.org/content/early/2012/05/25/1204026109 Proceedings of the National Academy of Sciences of the United States of America
Insects are small Arthropods in the class of insecta. (Online dictionary.com) The fact is that not all insets where small, in fact the well-known American cockroach’s Pre-historic ancestor the Blattoptera has been recorded to be six inches or longer. (National Geographic) The prehistoric that where so large became so large do to some advantages; they could ingest larger prey, and could defend themselves from a wider variety of predators. Also some reports state that the larger size of their bodies insolated heat more than a smaller one, enabling the body to withstand hotter tempetures. The larger body was due to the large availability of food. This cased the carnivores of the prehistoric-ages to become larger over time, to be able to consume the larger insects. (Nina Rastogi)
ReplyDeleteThere are no longer giant insects in the same scale that there once was. This is because planet cooled down during the ice age. To survive the ice age insects had to evolve and a smaller animal was more suitable to the new environment. The smaller animal was able to reproduce more and quickly because it took less time for the body to grow until its full-grown size. (Jack L. Conrad )Also the animals had to escape from the larger population of mammals arising and they could do this by shrinking because the predator could not see the insect and he insect could protect itself in smaller areas, which the larger predator could not enter.( ROBERT T. GONZALEZ )
• Why do we no longer have giant insect or why haven’t they grown back? According to American Physiological Society, the earth’s oxygen concentration is not as high as it was in the prehistoric age. The cockroach needs a larger concentration of oxygen to become larger and with global warming many species not just insects are becoming smaller do to this phenomena. (Jennifer A. Sheridan & David Bickford)
http://phys.org/news79804314.html(American Physiological Society)
http://www.thefreedictionary.com/insect
http://www.slate.com/articles/news_and_politics/explainer/2009/02/a_snake_the_size_of_a_plane.html (Nina Rastogi)
http://www.nature.com/nclimate/journal/v1/n8/full/nclimate1259.html(Jennifer A. Sheridan & David Bickford)
http://io9.com/5850741/climate-change-is-causing-earths-animals-to-shrink (ROBERT T. GONZALEZ )
http://news.nationalgeographic.com/news/2001/11/1112_TVbigroach.html
During the Permian era insects were huge compared to today’s proportions, boasting wingspans up to 30 inches across. There are different reasons why these prehistoric insects were so big. The cause was mostly due to the high levels of oxygen which helped fuel insect growth [Jennifer Welsh, 2012]. As more evidence of oxygen’s role emerged, we know these gigantic forms were extinct as oxygen levels declined drastically in that Permian era (Huey & Ward, 2005). [Bioteaching, 2012]
ReplyDeleteBirds played an important role within larger insects’ evolution. Such gigantic specimens were common 300 million years ago, but fortunately did not survive to pester us today. The evolution of birds from dinosaurs caused smaller insects to survive as they were more manoeuvrable to escape [Thomas H. Maugh, 2012] .
Researchers noticed the decreasing pressure in oxygen happened around the same time birds first took to the skies. About 150 million years ago, the “first bird” Archaeopteryx appeared, and about 25 million years later, the lineage had diversified greatly, meaning birds could fly and eat the huge insects [Jennifer Welsh, 2012]!
In conclusion, insects are no longer 6-12 inches long because oxygen levels declined and natural selection occurred. Insects needed more oxygen to grow larger. Also bigger insects were eaten up by birds. Only the smallest insects could survive by escaping the detection of predators.
References
Maugh , Thomas. "Los Angeles Times." Bird's evolution led to disappearance of giant insects, study finds. N.p., 24 Jun 2012. Web
http://articles.latimes.com/2012/jun/04/science/la-sci-sn-insects-birds-20120604
Welsh , Jennifer. "Why Giagantic Insects Shrunck to Modern Size." Predation and Competition. Live science beta, 4 Jun 2012. Web.
http://m.livescience.com/20735-giant-insects-shrunk.html
"Teaching Biology ." Gigantism in Insects. N.p., 4 Mar 2012. Web.
http://bioteaching.wordpress.com/2012/03/24/gigantism-in-insects/
There are many theory's revolving around the fact that insects, in prehistoric times we much bigger than they are now. The biggest theory is: the temperature size rule, stating that species in colder habitats tend to be bigger due to heat regulation. Another theory is that before in pre-historic times there was a lot more oxygen,when the oxygen levels started decreasing, so did the insects. Other theory's include that there exo-skeletons were not able to be stable when they were so big.Incredbly enough the giant insects would have a much easyer time to get Around since the air was much denser. Insects breath through thier tracias, the tracial system Works by diffusion, the mechanism of diffusion is that the bigger the mass, the less surface área meaning that it is less ifficiant. The oxygen theory has been views as the most valid and logical.
ReplyDeletesorce:http://rspb.royalsocietypublishing.org/content/early/2010/03/04/rspb.2010.0001.full
Adrian v.
ReplyDeleteWhy are insects so small?
Many things are involved in the size of insects. The first one is the temperature-size rule. This tells us species in cold environments tend to be bigger than ones in hot ones(1) . Another rule is the island rule. This one states that small animals isolated on mediterranean islands become bigger over time. It also says big animals become smaller (1).
Back in the Permian era, insects were giant because there was more oxygen in the atmosphere. This animals had enough biomass to support them for flight. The climate was more tropical and this helped the insects grow more. The amount of oxygen on the planet affects directly the size of insects (1), studies have shown this as well.
Other hypothesis say that insects are small because their respiratory system limits their growth (2). This is an unfavorable surface area to volume ratio. Another part that limits insects further grow is their exoskeleton. An exoskeleton limits their growth through molting. Something we know for sure, insects were bigger before. This is confirmed by the fossil record (1 and 2).
To conclude I can say insects have many limitations on todays earth for their growth. For starters, their exoskeletons molting and the oxygen levels on earth today. Also, their respiratory system and climate add to why they are so small (2). I would expect that millions of years from now insects will be even smaller than they are today.
1) Gigantism in Insects, 2012, Teaching Biology. http://bioteaching.wordpress.com/2012/03/24/gigantism-in-insects/
2) A sizeable advantage, Why are insects so small? 2013, http://amisstome.wordpress.com/2013/03/25/a-sizeable-advantage-why-insects-are-so-small/
Giant insects lived millions of years ago in the Carboniferous and early Permian Periods, but why are they not alive today and buzzing around the world causing chaos? Scientists have two reasons to why these creatures are not with us anymore. (Emily Howard, May 07, 2013)
ReplyDeleteFirst off and what seems to be a big contributor in the extinction and evolution of these giants, is of how the earth’s atmosphere has changed. During the Carboniferous Period, the planet was warmer, moister and contained more oxygen. The oxygen level during that period was about 30 percent of the air while today’s air only contains about 21 percent. Oxygen is important for insects because no insect has lungs; they rely on air flowing through a series of openings throughout their body which connect directly to tissues that need oxygen. (Emily Howard, May 07, 2013)
The second contributor in the extinction and evolution of these was the evolution of birds. As the first bird appeared on earth, they evolved to be faster and more agile than the giant insect. The birds could catch and eat the insects more and more causing the insects to go extinct or have to evolve to be smaller, faster and more agile to keep away from birds. (Emily Howard, May 07, 2013)
One example of a giant insect is the Meganeura. The Meganeura lived during the Carboniferous Period and is very similar to dragonflies today. It looked and acted like a dragonfly but it was about 10 times the size of a dragonfly. The Meganeura was classified as a griffinfly and had a wingspan that could reach up and over 75 cm. They are classified as griffinflies and not dragonflies due to morphological differences between the two. The higher amounts of oxygen during that period would supply a passive boost to the tissues which allowed insects to grow larger. As the oxygen levels decreased, insects would not be able to keep their large size causing them to evolve into smaller forms or to go extinct. The Meganeura is one of the largest known insect to ever exist. (http://www.prehistoric-wildlife.com/species/m/meganeura.html)
Another example of these incredibly large insects is the Arthropleura, a contender for the biggest arthropod of all time. It is related to centipedes and millipedes and has a crustacean ancestry as well. It, too, also lived during the Carboniferous period and into the Permian period. The dying oxygen levels had its toll on these gigantic creatures. The lack of vegetation did not just affect it because of the oxygen levels but it also caused there to be less moisture in the air. The crustacean part of this giant was dried out without the moisture causing the species to go extinct.
"Meganeura." Meganeura. N.p., n.d. Web. 01 Dec. 2013. .
"Arthropleura." Arthropleura. N.p., n.d. Web. 01 Dec. 2013. .
"Enjoying EarthSky? Subscribe." EarthSky. Emily Howard, 07 May 2013. Web. 01 Dec. 2013. .
Gigantic Insects
ReplyDeleteUnlike humans, insects take in atmospheric oxygen through spiracles, opening in the cuticle through which gases enter and exit the body, so the oxygen travel via the tracheal system, the insect’s respiratory system, and inside the tracheal system each tracheal tube ends with a tracheole, where the oxygen dissolves into the tracheole fluid; finally, oxygen then diffuses into the cells.
Back then in the Carboniferous and Permian periods, atmospheric oxygen concentrations were definitely significantly higher that they are today. Prehistoric insects breathed air that was 31-35% oxygen, unlike nowadays insects, which only have about 21% of oxygen in the air to breathe in. When the oxygen levels are higher, like in the Carboniferous and Permian periods, the tracheal system of insects can supply sufficient oxygen to meet the metabolic needs of a larger insect. Oxygen can reach cells deep within the insect’s body, no matter how long a insect measures, making atmospheric oxygen the most limiting factor on insect size.
Lloyd, Robin. "Why Bugs Are Not Huge." Live Science. N.p., 13 Aug 2007. Web. .
Guilfoy, Christine . "Giant insects might reign if only there was more oxygen in the air." . N.p., 11 Oct 2006. Web. .
"Why are there no really big insects any more? Blame birds.." the ranger's blog. N.p., 09 Jun 2012. Web. .
Insects have gotten smaller over time because back millions of years ago animals would try to get food (this is animals that were carnivores that would feast on other insects). This made insects become vulnerable when they were too big so because of this insects' genes throughout time would become more dominant the smaller they were. As time passed so did most insects become smaller. Firefles, for example, are an insect that got smaller because if they flew as large insects the birds would probably catch them, so they became smaller and more aerodynamic.
ReplyDeletehttp://www.mcwdn.org/Animals/Insect.html
There are lots of theories that explain why insects are not 6-12 inches. One theory is that insects' exoskeletons may not be strong enough to allow them to get much bigger. So they can become bigger there exoskeleton has to impossibly thick. Because exoskeletons are rigid, insects need to molt as they grow, shedding the old skin and growing a new one. Larger animals, particularly those without protective skeletons, would make for more attractive meals to a predator. Another theory suggests being larger makes you a more attractive meal, whether molting or not. A study found that the size of past flies decreased as birds evolved telling us that smaller creatures were better able to avoid hungry raptors and pass on their genes.
ReplyDeleteAnother theory says that insects breathe through tiny tubes called trachea, that transports oxygen from the atmosphere to the cells in the body cells. Once insects reach a certain size, the theory says, the insect will need more oxygen than can be shuttled through its trachea.
http://www.livescience.com/24122-why-insects-are-not-bigger.html
http://bioteaching.wordpress.com/2012/03/24/gigantism-in-insects/