Extreme Biology

by Ali

In Biology we recently did a dissection on the Dogfish shark. This lab was one of the most interesting because we were paired in groups of about four people and we would get our own shark to dissect and observe. In doing so we observed multiple things such as the incredibly large liver compared to the shark’s size. As we were dissecting we learned that the liver in fact provides buoyancy to the shark to help it not sink in the water. In this website it shows a diagram of a shark and explains in detail the structure and functions of the following: skeleton, muscles, digestive tract, circulatory system, gill and respiration, and the liver. An interesting fact as I was researching the dogfish shark was provided on this website and it stated that it was in fact the most common shark found especially in the North Atlantic Ocean.
 
What did you learn from this lab that you were not initially aware of about sharks? What other adaptations in structure did you find on the shark?  Did you discover any other interesting facts on sharks as you were researching?

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by Alex

Do sharks really attack humans on purpose or is it because of other reasons. There are different opinions on the subject, but what do you think? Answer that question before you read the rest of this post. Shark attacks do happen and people need to be aware of it, but not as humans make it out to be. Bees, wasps, and snakes are responsible for far more deaths each year than sharks (source).

There are three major kinds of unprovoked shark attacks. The most common are “hit and run” attacks. These occur in zones where there are many swimmers. The shark mistakes the human for something else and usually only bites once and then realizes it was wrong and does not return. Splashing, colored swimsuits, jewelry, and soles of the feet mixed with break surf and strong currents make it hard for the shark to realize what they are attacking. A shark must make quick decisions and quick movements to capture food. Most of the time the shark just mistakes the human for its normal prey. These attacks are seldom life threatening.

The next kind of attack is a “bump and bite” and “sneak” attacks. These are less common, and result in greater injuries and most deaths. This occurs in deeper waters usually and the shark circles the human to see what it is and bumps the victim before the attack. Repeated attacks are not uncommon, but this is a rare attack case. This is usually the result of feeding or antagonistic behaviors instead of mistaken identities (source).

Even though this is unlikely to occur here is a list of some safety precautions to take when going to the beach. Always stay in groups because sharks attack individuals more often, avoid being in the water during darkness, do not enter the water if bleeding, do not weary shiny jewelry because the reflected light looks like scales of a fish, and avoid constant splashing. There are just some of the safety precautions when in the water (source).

After seeing that video in class where they put the man into the clear tank and waited to see if a shark attacked and it didn’t that changed my view of sharks. Did that change your view on sharks and the commonness of them attacking humans? Why and when do you think sharks got this image of being human eating animals?

Check out this cool clip of sharks and human interactions. There are over 400 different types of sharks and most of them are not vicious.  The video (#4 located on the sidebar) shows the interaction between humans and sharks.

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by Connor

Who do you think would win this death match? If you guessed shark, you’re wrong. An octopus in the Seattle aquarium was put in a bigger tank full of sharks and other big fish. The marine biologists thought that the octopus would be fine with its camouflage, and if the sharks attacked, then the octopus could handle it. But, a little while after they put the octopus in the tank, dead bodies of sharks kept appearing in the tank. The biologists were puzzled, and decided to investigate, but what they found amazed them. They caught this footage of the octopus attacking the shark! After seeing that video, I’m not as scared of sharks anymore. But octopi are another story entirely.

The Octopus is really an amazing animal. According to one source they are strong enough to rip the tail off a shark (that is what was wrong with all the dead sharks- their tails were ripped off and their insides were gone)! Also, they are able to open jars and solve mazes and puzzles (and they taste good to boot!). If you want to know more then read here.

According to one article, the octopus has the most complicated brain of all the invertebrates. The octopus brain is estimated to have 300,000,000 neurons. These neurons are arranged in lobes and tracts that are more specialized than simple ganglia. An octopus has a “good” memory and can also learn (source). On the other hand, the shark’s nervous systems consist of a simple brain, spinal column and a network of nerves (source). Before researching this, I had no idea that octopi were this complex, but now I know the truth. It’s pretty amazing that these creatures are that smart, but you learn something new everyday. It makes me wonder what other animals are that smart. Only time will tell.

Do you think there are other animals out there with this level of intelligence?  Do you think it is possible for an animal’s intelligence to evolve to a point where it can learn and understand our language?  Would that be a good thing? Bad thing?

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by Miss Baker

Check out this hilarious video of pigeons playing ping pong courtesy of famed psychologist B.F. Skinner. What kind of animal behavior is this?

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by Peter

Why can’t you keep yourself from running into the donut store or up to your friend and getting a donut from them?  Or how the smell of your favorite pastry just makes you eat it, even though you know you should not?  Don’t worry, it’s not your lack of self-control; it’s your brain.

Research from Northwestern University’s Feinberg School of Medicine shows that a certain stimulus makes your brain react in different ways, thus causing you to eat a pastry that you other wise would not eat.  The experiment performed at the University tested the hypothesis that your body will make you react to specific stimuli.  One group of people gorged themselves on up to eight Krispy Kremes donuts until they could eat no more, while another group fasted for up to eight hours.  When the people that binged on donuts were showed the picture of the donut their brains were not registering much interest in the donuts.  On the other hand, when the people that fasted were showed the picture of the donut, two parts of their brain spiked with interest.

The Limbic Brain and the Spatial Attention Network both arose with interest when the subjects saw the picture.  The Limbic Brain is the part of the brain that is able to detect what motivates you.  “It says, not only am I hungry, but here is food,” said senior author Marsel Mesulam, M.D.  The Spatial Attention Network changed the focus to the desired object, the donut.  “If we didn’t have this part of the brain, every time you passed by a bakery you would have no control over your eating,” explained Mesulam.  “If your nerve cells fired every time you smelled something edible, then you’d eat all the time, not just when you’re hungry.”

I hope you don’t get too mad at yourself next time you have an irresistible urge or craving for your pastry.  Based on the experiment, what would you suggest is the best approach to be able to eat your favorite pastry and still keep from gorging on it?

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by Michael

Have you ever woken up to the sounds of birds singing or at least noticed their elaborate songs outdoors? Some birds’ songs are very complex and hit notes that we could never dream of. But have you ever wondered how they create such elaborate songs that last for such a long time? The secret is their syrinx or sound producing organ. Muscles control the songs detail so the more muscles a bird has around the syrinx the more complex the song. But unlike the human sound box, the syrinx is located much further down the trachea at the entrance of the two bronchi which leads to the lungs creating to separate sources of sound. The location of the syrinx allows the mixing of these two sound sources for greater complexity and variety in songs. Birds are able to sing so long because they can take a lot of mini breaths in between beats. Also the High Vocal Centre leads to this complexity. It is a nucleus in bird brains which sends signals for song production. The size of the nucleus can change therefore causing increased or decreased song complexity.

When you think of pollutants and animals what do you normally think of? Probably negative affects. Researchers at Chardiff University have found male wild birds who prey on certain pollutant-affected organisms have more complex songs. European Starlings foraging at a sewage plant were studied. Synthetic and natural estrogen were among the pollutants found at the plant. These pollutants affect the High Vocal Centre of the birds brain which controls song complexity. Estrogen receptors were increased in this area of the brain causing that part of the brain to be larger.

Increased song complexity attracted more females for reproduction to the male birds. This is a favorable trait that would cause birds exposed to the pollutants more likely to reproduce. However, the pollutant could have caused a drop in immune system efficiency. Still this is a favorable trait. It is amazing how we can affect entire populations in such a way due to pollutants. This is why we must be so careful as to what we do to our environment.

What are some other ways pollutants effect populations?  What effect could this have on bird populations and species? Could this affect other species and organisms as well?

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by Jacob (AP Biology) 

Crazy stuff huh? You think, wait, if I am blind then how can my offspring not be [blind]? Well, a study at New York University showed that through mating different populations of the species, Astyanax mexicanus, or blind cavefish, some of their offspring could see.

These cave fish diverged many millions of years ago from regular fish and a certain mutation in the diverged fish made it lose its sight.  Natural selection let those genes be passed on through several generations until today. Although natural selection made the blindness in cave fish become the prominent trait, the ability to see was still in the gene pool.

By mating two differing populations of cave fish the trait to see had a larger chance to be produced. This is because the code for the cavefish to be blind in DNA is determined by multiple genes and in the different populations of cavefish they have different sequences of those genes that code for blindness. When two different populations are mated, the genes that cause blindness can be replaced in the offspring generation by the genes that both parent fish have that do not cause blindness.

Let’s say that the presence of just one homozygous recessive gene causes blindness.  If a group of genes represents two blind fish, AABBcc and AAbbCC, and these two are mated, a possible offspring could be AABbCc.  Because the recessive genes are now hidden in the heterozygous condition the offspring would have the ability to see. This finding can be used to help scientists understand the human eye better and help prevent blindness.

Astyanax mexicanus or the Blind cavefish is not endangered but it is a threatened fish. They grow to around 8 cm. in length. They live around sandy, rocky backwaters of creeks and small rivers. They eat worms and insects. They are normally found in Texas through Mexico. Check out more on the Blind cave fish at this site.

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by Josh (AP Biology)

Some DNA in our genome that comes from ancient viral infections has surprising effects on our bodies and even can help a mother have a healthy pregnancy. Retroviruses insert copies of its genome into the host cell and then infect the cell which cannot be reversed and possibly lasts lifetimes. If a sperm and egg cell, which are examples of germ-line cells, are infected, then the virus can pass itself down through generations. This can cause endogenous viruses (ERV’s) to be able to possibly live for millions of years.

“Over the course of evolution, retroviruses have invaded the germ-line of our ancestors on numerous occasions. Now, human ERV’s (HERV’s) make up around 8% of our genome,” say Dr David Griffiths from the Moredun Research Institute and Cécile Voisset from the Faculté de Médecine et des Sciences de la Santé in France.

Now however, there are none of these viruses currently infecting humans, but there are some that infect animals. A breakout of neoplastic disease has infected Australian koalas, which gives scientists a great way to study the process. “It is only recently that the abundance of HERVs has been recognized and we are learning that they can have significant functions,” says Dr Griffiths.

What benefits could these ancient retroviruses possess for human kind?

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by Kelsey (AP Biology)

When you think mutations, you automatically think of bad connotations, like scary monster mutants, or the teenage mutant ninja turtles, or human mutations that can make life very difficult for some people, but mutations can be extremely beneficial and are necessary for natural selection and evolution.

Part of evolution is natural selection.  But natural selection cannot create new alleles, the alleles already have to be present.  So how do you get new alleles to be selected? Mutations!  Not all mutations are life changing; some can simply be a different fur or eye color on an animal.  This creates new alleles so that evolution can occur.

The new alleles that mutations cause can actually be very beneficial to the organism.  For example, a panda’s “thumb” is actually an enlarged bone in their wrist.  If that bone is mutated, so that it is larger than normal, it helps the panda break and reach bamboo better than a normal “thumb” would have been able to.

Another example is when bacteria become antibacterial resistant.  Obviously, this is great for the bacteria, not so great for us.  As we come up with new antibacterials, bacteria are evolving to resist these.  The reason they are able to survive the antibacterial is because of mutations.  The bacteria that have random mutations that make them resistant to antibacterials survive and are naturally selected to reproduce.  Over a long period of time, evolution will occur and the whole population will be resistant.