Biology

Does cracking your knuckles really cause arthritis?

There is no evidence that it is the least bit harmful. It is often annoying to those who don’t crack their own knuckles, and perhaps that is partly where the myth that it is harmful started. What is happening is that when you seperate two bones by pulling or sharply bending, you are creating a space almost like a vacuum. There is a small bag of synovial fluid that stretches and a small bubble of carbon dioxide is released inside it. This is what produces the cracking noise. Read more…

What is hydroponics?

 The Latin term “hydroponic” literally means working water. It basically means growing plants in any medium other than soil. All plants require inorganic nutrients such as potassium, sulphur, magnesium and nitrogen and in hydroponics, these nutrients are often provided through a liquid or gel solution. Read more…

What is the most venomous animal?

First, we should address the difference between venomous and poisonous. Most poisonous animals have toxins on or in their skin. They may secrete toxins that would be deadly to the touch – for either humans or other animals. So for poisonous animals, many scientists agree that the poison dart frog and some salamanders are the most poisonous. As little as two micrograms of toxin from the poison dart frog could kill a human.

A venomous animal also has toxins, but is typically delivered by biting, stinging or stabbing. While this is sometimes debated, the box jellyfish is often considered the world’s most venomous animal. You may have heard of the inland taipan of Australia as being very venomous, and it is. It is considered the most venomous land snake in the world.

Sources: Wikipedia and the discoverymagazine.com Dear Digger Doug Q&A.

How much electricity does an electric eel generate?

The quick answer is that a mature electric eel can produce a shock up to 500 volts at 1 amp of current (500 watts).  The eel’s organs are capable of producing two types of electric discharge– low voltage and high voltage. Both could be harmful to an adult human.

The longer answer, or exactly how the electric eel produces electricity is a bit more complex. Basically, the electric eel has three abdominal pairs of organs that produce electricity. They’re called the Sachs organ, the hunter’s organ and the main organ. The eel’s vital organs are contained in the first one fifth  of its body whereas these electricity producing organs are in the remainder four fifths.

These organs are made of electrocytes lined up in series so the current flows through them and produces an electrical charge. When the eel locates its prey, the brain sends a signal through the nervous system to the electric cells. This opens the ion channel, allowing positively-charged sodium to flow through, reversing the charges momentarily. By causing a sudden difference in voltage, it generates a current. The electric eel generates its characteristic electrical pulse in a manner similar to a battery, in which stacked plates produce an electrical charge. [wikipedia]

Which mammal has the shortest gestation period?

The shortest known gestation period is 12 to 13 days. This record is shared by three marsupials, which is kind of an unfair comparison to all other mammals as in marsupials, the young are born immature and have to continue developing in a pouch on the mother. The three mammals with this very quick gestation period are:  the American or Virginian opossum (Didelphis marsupialis); the rare water opossum, or yapok (Chironectes minimus), of central and northern South America; and the eastern native cat (Dasyurus viverrinus) of Australia.

More about the Virginia Opossum [source: Wikipedia]

It is the largest member of its genus, family and order and is the largest of the opossums. They are typically 15–20 inches (38–51 cm) long and weigh between 9 and 13 pounds (4–6 kg). Their coats are a dull grayish brown, other than on their faces, which are white. Opossums have long, hairless, prehensile tails, which can be used to grab branches and carry small objects. They also have hairless ears and a long, flat nose. Opossums have 50 teeth and opposable, clawless thumbs on their rear limbs.

How did the zebra get its stripes?

Another interesting question to first consider is: is a zebra a light animal with dark stripes, or a dark animal with light stripes? It’s generally believed that a zebra is a dark animal with light stripes. Most scientists believe that the zebra evolved from a horse-like animal with no stripes.

One theory of where the stripes came from is simply natural selection. Over millions of years, a few zebra foals were born with lighter colored stripes in a process called “accidental variation.” These foals had a marked advantage over their darker colored siblings and thus went on to reproduce in greater numbers, creating more striped offspring.

But how exactly did having stripes create an advantage? Think of an ordinary dark colored horse standing on a hillside. Its silhouette would make it stand out from the background, and would tell a hungry lion exactly where his next meal might come from. Now imagine a striped animal. It’s silhouette would be a bit more mottled and generally different. This likely gave it a camouflaged advantage and probably spared a few animals from hungry lions.

A couple of good sources of information on zebra biology are: Developmental Biology, and the Wikipedia article on zebras.

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What was the Scopes Monkey Trial?

John Scopes was a high school biology teacher who was brought to trial in Dayton, Tennessee in 1925 for teaching the theory of evolution. He was protesting a state law that made teaching anything that denies the divine creation of man. The trial may be considered the first of what we would today call a media circus. Scopes was found guilty and sentenced with a very moderate fine but the decision was later reversed. The law remained on the books in Tennessee until 1967. Read more…