How come insects grew to massive sizes in the past  but not now?
546986
Nobody really knows. One explanation is that oxygen levels in the atmosphere were higher in the past for reasons we don't understand. That is supported to some degree by isotope ratios in rocks. With higher oxygen levels insects could grow larger without running into problems of gas diffusion.\n\nThe other hypothesis is that the greenhouse world that existed when the giant insects did was incredibly productive and allowed for extravagant solutions that would  not be energetically feasible today. For example insects today can achieve limited active respiration by pumping their abdomens  but it is amazingly wasteful of energy. However in world with limitless food that may not have been limiting. That theory is supported to some degree by the fact that the giant insect fossils only turn up in the equivalent of rainforest locales, IOW in the most productive areas of the planet.\n\nIt is worth noting that the giant insects seem to have come and gone at least twice. They were common in the Carboniferous and then died out and re-emerged around the Silurian. That suggests that whatever was limiting them was somehow recurring.
634300
Yes, cockroaches are the only living thing which doesn't undergone any evolutionary changes till now.\nIt just adapt itself to any type of environment.
542946
sure they were, this is clear because of the evidence we've got from geology. the bones we've found don't lie. but something you should notice, and that is dinosaurs were not all huge wild animals, they were just a kind of animals, including all sizes and all behaviours. also it is believed that some of the animals living nowadays are the children of ancient dinasaurs.
575699
Insects do not have an internal skeletal system, they have exoskeletons.  So all insects are invertibrates.
1019223
It's not entirely believable that we evolved from apes. If you have ever actually looked into the question you would know that animals do evolve. I'm a Christian and still don't refute the facts that "survival of the fittest" is an actual scientific process. People don't evolve from ants because they have an entirely different make-up than people. Ants have an exo-skeleton while mammals do not. One good example of things evolving are moths. During the industrial revolution in Europe many objects (trees) became covered with a light soot. The moths used to be able to camoflauge themselves on tress but couldn't anymore because of the soot on the trees. Survival of the fittest was demonstrated because all of the darker moths that blended in with the trees were not eaten by preadtors. When these dark colored moths began surviving they reproduced and their offspring were well-suited to their environment due to their dark color. Evolution can not be denied. How can you explain how some animals must be "2 sexes" so that they can ensure their population can continue? It's obvious that at one time those types of animals were either male or female and had to "evolve" to survive. The whole theory behind evolution is: "Those that are best-suited to their environment will survive." Maybe not all monkeys had problems with predators as others did, which means they had no reason to evolve. Darwin broke-it down very easily and demonstarted a gradual change that developed us into humans.
1160495
Thank God you are not!\n\nEvolutionary biology is mindless, only humans of what we perceive now as "normal size" were most fit for life circumstances, very small were too week, too large were in need for more food, which might not be always readily available, so the small ones would be killed and the large ones would starve to death! Another explanation would be that the large ones ate the smaller ones! So we lived until now! Is that plausible?
742911
They were average height of around three inches for females and four inches for men. Every thing they had was tiny. They had little bittie hands and little bittie feet. The had voices like fairies and as a matter of fact that is where fairies came from. It wasn't fairies at all it was people riding butteflies. It became quite a sport because people just loved to travel from flower to flower on the back of a monarc. At night they would ride moths that glowed in the dark and make trails of beautiful colored light when they flew. It was where they got the idea for fairie dust. It was because of steroids that people became big and with that got big ideas about wars and killing and stupid stuff like that. It was the idea of some genious that put the stuff in the water system and ruined the joy of butterfly riding. It is all relative, other then the ideas, because everything else got bigger too to accomidate the size as it enlarged. We really are that small still because the other day when I was riding an airplane I looked out the window in Chicago and I saw the little people running all over the place and then even had little cars and busses, etc So I suppose it is all in the perception. We are only as big as we think we are today and 100 years ago.\nAfter you read this, then go outside and hold your thumb up in front of the moon and you will see what I mean. you can put the whole moon behind your thumb.\nHope this gives you some insight.
593057
When locusts aren't being locusts they are just grasshoppers. They are not bugs. \nI have no idea what Figure 19 is. Here are some links with life history stages of grasshoppers or locusts depicted and explained: \nhttp://www.library.ubc.ca/ereserve/biol120/locust/locust.htm\nhttp://www.sdvc.uwyo.edu/grasshopper/ghlcycle.htm\nhttp://www.4to40.com/earth/geography/htm/insectsindex.asp?counter=16\nHere are some scientific articles on "Locusta migratoria" "life history" \nhttp://scholar.google.com/scholar?q=%22Locusta+migratoria%22+%22life+history\nLocusta migratoria is the species name of the locust that plagues Africa. Life history is the term generally used by scientists, rather than life cycle. I would link to the best articles, but not all of them are accessible to the general public--you would need to be on a university computer network like me.
606443
The spiders in my back yard have reached the size of small cats.  I'm not sure if it's global warming or the steroids my wife dumped out last year.
44204
No, living things 're'turn to dust, meaning that the net weight gain is 0.  The Earth's mass does increase slightly (relative to the size of the Earth) from all of the space dust and meteors that constantly burn up in the atmosphere and fall to the ground.
215464
Birds had already evolved from a group of relatively small predatory dinosaurs by the Jurassic (that is, the middle of the Secondary Age). No one knows for sure what killed many species (not only dinosaurs) at the end of the Cretacic Period (several million years after the origin of birds) but it was probably a combination of factors, including the large meteor. Maybe you're picturing the meteor as a gigantic bomb that just wiped everything from the Earth, but although the local effects of the hit must have been devastating, the rest of the world experienced other effects (such as darkening clouds) that were more gradual but also more lasting. \nThat being said, all species have finite existence, and the reasons for extinction and survival are many. Mass extinctions are like extraordinary combinations of the "ordinary" background extinctions that happen all the time in an evolutionary/geological scale. \nIn the Secondary/Tertiary boundary, many large animals went extinct while smaller ones survived (including us mammals!), so ecophysiological characteristics of those species may have something to do with their extinction (perhaps the meteor combined with other environmental changes). \n\nIf you're interested, there are good Evolution textbooks (Ridley or Price are modern classics) that deal with the different extinction patterns and factors.
885295
They have been affected in many ways... First and foremost, they were called "Humongous Pandas" about 200 years ago before pollution sadly shrunk them to their current Giant size.\n\nGlad I could help you on this topic.\n\nJohn Z
8843
it has been expanding for 14 billion years
607969
The fossil record doesn't show any kind of trend towards smaller body size in the hominid lineage.  The earliest hominids, like Australopithecus afarensis, were much smaller than we are now, perhaps only 3 or 4 feet high.\n\nIf anything, the trend has been towards larger body size.  Homo sapiens in general is taller than Homo erectus was, which was taller than Homo habilis and so on.\n\nEven the off-shoot population of European neandertals were shorter than average human stature, but had more massive bones, with higher density than ours, and may have been noticeably stronger.\n\nThere was one off-shoot that may very well have shrunk in size.  Homo floriensis was discovered a few years ago as remains on an Indonesian island, and appears to have been a dwarf form of human.  Dubbed the 'Hobbit' by the popular press, it may well turn out that this was a tiny species of human, only 3 foot high, that lived in the area at the same time as Homo sapiens sapiens.\n\nDwarfism is a common adaptation found in island species isolated from the mainland.  Dwarf forms of elephant once existed on Malta, and a dwarf mammoth survived on Wrangel island until only 5000 years ago.\n\nUnfortunately, only two workers really examined the Homo floriensis fossils.  One is the dude who put forth the claim of a new species, and the other one claims they were just the remains of a regular human who suffered from dwarfism.  The fossils were smashed beyond recognition on the trip back, and each researcher blames the other.  And then the Indonesian government refused all research permits for the area since that time.  So we're still waiting to hear for sure as to what those fossils mean.
1134801
Relationship to other primates had been suspected for years before Darwin   (1840's)-- simple observation.  Now with the deciphering of the geome for both chimps, and humans, relationship has been proved beyond a shadow of a doubt.  We are all so similar even back to fish ---a central body with 5 protrusions -- head and 4 limbs.  I don't know it all, lady, but taught science and math for years, read Discover Magazine, Scientific American, and watch the Science channel.   Fascinating.... Evolution is no longer a theory, but a fact, a lovely fact.  Our medical research on rats, dogs, and other critters would be worthless if evolution were not..   Helpful?  The question is toooo complicated to fully explain.  But you can start by reading scientific journals....   Good luck  Life is a life-long learning process.....  and god has nothing to do with it.  Critters survived, and evolved.  If a gene were detrimental, the critter carrying it didn't live long enough to procreate.  It the mutated gene was beneficial, it aided in that critter to live long enough to reproduce.  Lots of evolution is even occuring today.  Google things like Darwin's Finches, pigmy elephants, and of course dinasaurs.  \n\nOne quick interesting thing about moths in England to illustrate evolution:  In the early 1600's, before the Industrial Revolution began and coal producing smoke was a fact of life, a particular moth was mostly white, and blended into the tree bark on which it laid its eggs. The tree bark was white. Occasionally a grey-black one was hatched, but never lived very long -- birds got it.  As the Industrial Revolution took off in England, producing black soot, that black soot began to cover the trees' bark.  In less than 150 years, the white variety was gone, and there existed only the darker mutant.  Beginning in 1950 when England passed anti air pollution laws, those trees began loosing the soot off of the tree bark.  Yup, you guessed it..... the white variant is now dominant........ evolution in action  ,,,,,Helpful????
268244
This a classical  example of ecological genetics. As a result of coal burning in industrial revolution the habitat of the moths were blackened with soot. As a result more black pepper moths were surviving because they blended in better.( pre industrial there were 99% white, post there were 98 % black) Now days with better technology and less coal it is being reversed because lichen is now able to grow on trees and the white can blend in better.
1035644
They all change once married, and are unrecognizable afterwards.\n\nIt's a bigger change than the pupae changing to an adult insect.  A cute little white inching bug climbs out of the cocoon as a digger wasp!  Ye Gods!