The key levels of organization involved in breathing.






Hungry and satiety: a deeper look.

It’s natural to feel hungry when you need to refuel your body, or to feel satisfied when you are refueled.  But think deeper, how are we able to feel hunger and satiety?  Various organs, chemicals and mechanisms contribute to the feeling you get when either hungry or satisfied.

Hormones signal the satiety (satisfied)  part of the brain, depending on whether the body needs nutrition, or whether it’s satisfied.  The hormone called Ghrelin, sometimes known as the “hungry hormone” is the chemical released by the stomach when the stomach is empty, and it is continued to be released until the stomach is stretched out or satisfied.  When you miss a meal, and begin to feel hungrier and hungrier, it is when ghrelin is collectively released by the stomach.

What about the feeling of satiety?  The hormone insulin, is released by pancreas when blood sugar is too high, and it actually suppresses the appetite.  Figuratively, insulin is telling the brain that it has consumed too much sugar for now, and sending signals for it to not consume anymore until further notice.

There is another hormone called Leptin.  Leptin is released by adipose (fat) tissue, and this chemical also suppresses appetite.  Levels of leptin are actually decreased with loss of weight, which could explain why it is hard to maintain a diet with the intent to lose weight.

Another important hormone is Peptide YY, or PYY.  PYY is secreted by the small intestine when the organism finishes consuming a meal.  PYY counteracts the effects of ghrelin, and suppresses the appetite.

In conclusion, hunger and satiety are much more than just a growl  in the stomach.  There are a lot of chemicals and mechanisms that signal the brain and tell it what the body needs.



What does it mean for a creature to be intelligent?






Should all the species in phylum Arthropoda be classified under one group?

Arthropoda is the largest phylum in the world, with over 1,000,000 known species.  This group of creatures possess multiple common characteristics that justify them to be classified in the same group.

On the Linnaean scale of classification, phylum is the classification directly below the kingdom classification.  Among arthropods, there are multiple different classes and sub-phyla. Some of these include: crustaceans, insects, and arachnids.  Some common classes of arthropods are lobsters, crabs, beetles, winged insects, etc. Sub-phylum, chelicerata, contains the class arachnid, which includes spiders, ticks and scorpions.

There is tremendous diversity within this phylum, however, they all share a basic body plan. There are variations among different classes and species (and especially the sub-phylum arachnids), but they all follow one basic blueprint.  Each further classification is specialized with different vices, but still share basic characteristics.  What is this body plan? Arthropods have a full body exoskeleton, and jointed limbs, and three separate body cavities: a head, a thorax, and an abdomen. –With the exception of arachnids, that have a joined head and thorax, called a cephalothorax.

As many species as there are within this phylum, one can imagine the incredible diversity of arthropods.  There is so much detail we already know, and there are so many details mankind has yet to discover.

All these species being classified into one group poses the question: should they all be classified in just one group?  Yes, they should all be classified together.  Why?  Because they all share the same basic structure, and engage in similar behaviors.  This body plan gives them similarity, and even though the basic structure varies tremendously, the species all have similar behaviors and metabolic processes.  The body blue print of arthropods preserves the relationship between all the species within the phylum.