For class we began reading the book Life on a Little Known Planet by Howard E. Evans. This book is about the magnificent natural world that our earth offers to us. The book is directed towards the general public so that they will understand the world a little more. Although Evans states that there is so much to our world which is unknown, he attempts to breakdown the known information on insects to people. Evans believes people should know more about these crawling creatures since the pyramid of numbers basically puts them near the bottom near bacterias, producers, and protists (Evans 30). The pyramid Evans describes resembles a hierarchal structure where the higher up you are among the pyramid the less populous you are. Evans wants people to see the vastness of insects among the earth, and if people recognize this ubiquitous spread of insects among the world then potentially more people will become enticed by these marvelous creatures and want to discover more about them. Evans believes people should take the time to study what the world has to offer us; what life offers us and many other organisms. Evans really digs into the insect information beginning with a chapter on springtails. Evans probably begins his chapter with this non true insect (although they are evolutionarily closely related) because these are the most numerous species on the planet besides mites, and yet ordinary people living day-to-day lives have probably never known about this animal (Evans 32). Specifically, that's exactly what Evans attempts to do throughout his book, prove to people all these unknowns about our natural world, and he starts so by talking about a creature that is everywhere and no one knows of it. I found the springtails to have some interesting information. First of all, I recognized throughout the chapter the distinctions between most insects and the springtail organisms. Springtails are missing a common evolutionary adaptation for filtering their hemolymph and uric acid. Also, springtails have six abdomen segments compared to an insect's eleven. Lastly, springtails' development as an embryonic egg is different than true insects. Springtails do not undergo the same cleavage furrow formation as insects do, and I wonder if since their cleavage is different and I know they are protostomes since insects are, but are their coelom formation different than that of a true insect (Evans 35). Besides the distinct differences between the two groups evolutionarily, springtails do have one interesting tactic that I found to be cool. All insects are very chemical sensitive through their sensory organs: antennae. their tastes, etc.; however, springtails can use their chemical senses to change their coloration and to change the composition of their blood (Evans 38). These defense mechanisms are useful throughout their survival. The mimicry the insects use hides them from potential predators and also allows them to send warning signals to predators to avoid being eaten. Another tactic the springtails use is "reflex bleeding" where they change their blood to become toxic when attacked (Evans 38). This one mechanism really impressed me because it verifies just how sensitive insects and similar groups are to chemical structures. These springtails have control over their internal system in order to allow them to physically manipulate and change the orientation of molecules within their hemolymph to become toxic. That aspect is unbelievably impressive, and these springtails need to be recognized for their success in their survival strategies.
Figure 1.
I. Jesse works within the entomology department of Iowa State University and provided the picture (above) of the springtail.
Besides just springtails, Evans, in the beginning, also addresses the cockroach. These creatures love being in places where there is an abundance of food, and most commonly they get into people's houses from their groceries (Evans 60). To think that every roach you have killed in your house probably came home with you and all of your groceries - disgusting. In addition to that fun fact, cockroaches have been experimented on to discover their intelligence. These creatures can even solve mazes and have the capability to learn without their heads (Evans 52). I wondered how these creatures can survive without their heads, do they not have a brain? Well my teacher explained to me that these specimens do have brain(s) technically. Their nervous system is not centralized since they are not evolved enough to have such a nervous system, but they have ganglions and sort of a circuit type nervous system. Imagine many brains spread throughout your body in a parallel circuit formation, since each brain is independent of the other.
Figure 2.
Above is a depiction of a simple parallel circuit. The battery would represent the roach's head, while the four resistors would represent the roach's other brains (ganglions). If one were to go out the others would always still be functional.
This is how the cockroach can still function, even without its head. That is one interesting piece of information that I did not yet know, and it will serve a purpose for next time that you think you killed the pest in your house.
Above are the different species of cockroaches commonly found here in America.
Image provided by the Centers for Disease and Control Prevention
http://www.cdc.gov/nceh/publications/books/housing/figure_cha04.htm
I like the battery analogy. Good stuff!
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