Do Whales and Dolphins sleep ?

When my son was in first standard , he  came to me asking this question , " Whales and dolphins are mammals. They breathe air through the nostrils located on top of their head ( called blowholes). Then can they sleep ? If they go underwater and sleep , how would they breathe ? Would n't they die if they forget to come to the surface of the water for breathing ?

I was little puzzled as I did not have the answer . I googled and explained the reason to him. Thanks to the technology advancement that parents have the right  answer at the click of the button ! Children have the ability to question  status quo which probably we adults lost over a period of time. The inspiration behind this blog is  my son. May be useful to all other parents and children too !

Answer is beautifully explained in "Howstuffworks".

­Whales and dolphins are mammals, so in a lot of ways, they are just like human beings.­ Among other things, they have similar bone structure, are warm-blooded and give birth to "live young." The biggest differences between these animals and human beings are related to our respective environments. Whales and dolphins have a unique respiratory system that lets them spend long periods of time (sometimes 30 minutes or longer) underwater, without taking in any oxygen. ­

­On land, human beings and other mammals breathe involuntarily: If we don't make a decision to breathe or not to breathe, our body will take in air automatically. Because of their undersea environment, whales and dolphins must be conscious breathers: They have to actively decide when to breathe. Consequently, in order to breathe, they have to be conscious. This presents a problem, since mammalian brains need to enter an unconscious state from time to time in order to function correctly (see How Sleep Works to find out why this might be).

­­There's plenty of time for a dolphin to catch a catnap between trips to the ocean surface, of course, but this isn't a viable option. When you're a conscious breather, it's just not feasible to be completely unconscious -- what if you don't wake up in time? The solution for whales and dolphins is to let one half of the brain sleep at a time. In this way, the animal is never completely unconscious, but it still gets the rest it needs.
Scientists have studied this phenomenon in dolphins, using electroencephalography. In this process, electrodes hooked up to the head measure electricity levels in the brain. The resulting electroencephalograms (EEGs) of dolphin brains demonstrate that in the sleep cycle, half of the dolphin's brain does indeed "shut down" while the other half is still active. Researchers have observed that dolphins are in this state for approximately eight hours a day.

We can't really know what this rest state feels like, but we can make a good guess. It is probably something like the semi-conscious state we experience as we begin to fall asleep. We're pretty close to unconsciousness, but are aware enough of our surroundings to wake up completely if we need to.

And where do dolphins and whales sleep? They could probably sleep anywhere, but it makes sense that they would do it near the surface of the ocean so they can come up for air easily. It's not uncommon to see dolphins "logging," swimming slowly along the surface, with very little movement. Presumably, these are dolphins at rest.

Interesting , is n't it ?

Does cutting down trees affect rains ?

My son asked me the other day, "Does cutting down trees affect rains?  

Yes. It does. Trees are necessary for rain. Trees creates cold and humid atmosphere required for rain. 

Water from ponds, lakes, rivers, seas get evaporated due to the heat of the sun and rise as water vapor.   As we go up in the atmosphere, it is cooler. So, at maximum height in the atmosphere, the water vapour in the air condenses and tiny water droplets are formed. These tiny water droplets floating in the air along with dust particles are called clouds. As the clouds move up further, it is even cooler. Water droplets come together to form larger water droplets. The larger water droplets are so heavy that air cannot hold them. There fore they fall down as rain. If the temperature is very low, the water droplets freeze in the atmosphere and fall as hail or snow. The coming down of water in the form of rain or hail or snow is called precipitation.

Important thing to note is that the water vapour is also added by the plants through a process called transpiration. Let is look at what is transpiration. 

1. Transpiration is the process by which plants return water to the atmosphere. After absorbing water from the ground, plants release water through their leaves. Transpiration helps plants stay cool, in the same way perspiration keeps humans and animals cool.

2. Plants and trees have pores on their leaves – stomata – which enable the exchange of gases such as carbon dioxide between the leaves and the surrounding air.  When stomata open, water droplets are released and usually evaporate from the leaf’s surface. This process is known as transpiration and provides an important source of moisture for cloud formation and rain. 

How much water do plants transpire?

An acre of corn gives off about 3,000-4,000 gallons (11,400-15,100 liters) of water each day, and a large oak tree can transpire 40,000 gallons (151,000 liters) per year.Large rainforests (and their humidity) contribute to the formation of rain clouds, and generate as much as 75 percent of their own rain.

This continuous movement of water from the earth's surface, water bodies and plants as water vapour to the atmosphere and back to earth's surface as rain hail or snow is called water cycle. This cycle maintain the supply of water on land.

So, trees play a very important role in maintaining the supply of water.  Let us conserve trees.