Why can't red beans grow into anything other than red bean plants?

Nagashree was talking to me about Classification of Plants and animals yesterday. The following question came up: If you look at two varieties of bean plants (say red bean and brown bean) just when they sprout, they look similar. But when they grow up they produce different varieties of beans. The red bean variety always produces red bean plants and the brown ones always produce brown bean plants. What is in the bean seed that determines what the plant grows into ? And what is the process involved?

Nagashree, try to find more on the above question.

A related question: Certain lizards re-grow their tails when their tails are cut off. Why does that not happen to most other animals?

How is information stored in hard, floppy, optical discs etc?

Srinidhi asked the question: How is information stored in hard, floppy, optical discs etc?

At a high level this is what every storage device (like floppy disks, hard disk drives, optical storage media like CDs, DVDs, BluRay disks, etc) does: They store sequences of 0's and 1's.

There are several ways of storing 0's and 1's. One way is to take advantage of magnetic properties of materials, like in floppy disks (Have you seen them? Nobody uses floppy disks these days!), hard disk drives etc. Optical drives use the method of creating microscopic "pits" to represent to mark 1's on plastic. These pits could be just markings that could be rewritten.

Have you played with magnets, Srinidhi? If you play with a couple of magnets for a while, you will notice that they have poles. You know very well that every magnet has North and South poles. You can make certain materials magnetic by subjecting them to a magnetic field. That means you can make them possess a N-pole and a S-pole simply by putting them in a strong magnetic field. You can also reverse the direction of poles in such materials(Why?). Let us look for examples of such materials.

Now imagine millions of such tiny magnets on a very small disk. And imagine a magnetic head that can provide the magnetic field necessary for these tiny magnets to change polarity. This is what a magnetic disk is, in principle. The magnetic head goes about providing the field needed to set the magnetic polarities as desired (say, N pointing up to indicate 1 and down to indicate 0, etc).

Optical disks use lasers to "burn" pits on a plastic disk. A less intense laser can be used to read the same pits.

This just to state the principles involved. The details, when the principles are implemented, can be mind boggling. Just take a look at the following article to get an idea of what is involved: http://en.wikipedia.org/wiki/Hard_disk_drive

New Home to Putkutti Science Club

The website https://sites.google.com/site/putkutti/home is not quite suitable for multiple authors posting articles. I thought this would be a good one to use for discussions. We can use the earlier site for writing lengthy articles and use this blog site for discussions.

Send me an email if you have difficulties using this blog.