Why are whales so big?

[jeeprasr]

Actually the reason that whales are so big is related to the medium that they live in. Water provides buoancy so the gravitational pull of a large body isn't the same issue that it would be on land. Also, life in water means that the animal must find a way to reserve body heat (heat is lost about 20 times faster in water than on land). As you increase body size, the surface area to volume ratio decreases, thereby decreasing the amount of area that heat can be lost across. So, a larger body means less heat loss. Whales also have a thick layer of blubber to help minimize heat loss which also contributes to a larger body size. Most large whales migrate and therefore will encounter colder offshore waters at some point. Therefore, thermoregulation is very important.

[psr]

Jeep,

Thank you for that insightful and extremely educational reply to this puzzling question. I would like to inform you that I have taken an exceptional shine to you. I like smarty pants'!!!!!!

psr

[jeeprasr]

Aw shucks psr, that's sweet of you. It just happens to be a subject near and dear to my heart. Now, if the question had been about car repairs or a recipe for a good zucchini bread, well I would've been stumped.

Jeep

[psr]

Jeep.....

Zucchini bread??? Hmmm......my culinary skills must be sadly lacking.....

psr

[Paul Ward]

Hi jeeprasr and thanks for your comments. You've answered the how-so-big, but I was inteerested in the "why now?", why not ever in the past?

I guess the answer is tied up with the need for so much food requiring such long journey's a high metabolic rate and the need to be a warm blooded mammal to be so active in frigid waters. A question of which came first, the requirement to enter frigid waters to support the food requirement or the being warm blooded and large enough (as a result of enough food) to be able to enter frigid waters.

Then again, seals can do it too - while feeding on krill, and they are much smaller.

[Maria.]

Foudn this on the Internet. Interesting . . .

The secret to it all is their aquatic environment. The average blue whale
for example is 85 feet long and weighs 106 tons, which is as much as 4
Brontosauri or 30 elephants. Other large baleen whales such as fin and
sei whales are much smaller than blue whales (tipping the scales on average
at 58 tons and 13 tons respectively),but they are still considerably larger
than the largest living terrestrial animal, the elephant. The reason whales
are able to support such weight is the buoyancy of the water in which they
live.

The heavier an animal is the greater its relative surface area. The power
of the legs and muscles which help support an animal is a function of the
surface of their cross-sections. As the total weight of an animal increases
a point is reached where the legs would just collapse. So once a certain
maximum weight is reached, life on land becomes impossible. The situation
is quite different in water however, where the buoyancy counteracts the
gravitational pull on the body. But note that even aquatic animals have
some limits on the size they can attain, for the surface area of the lungs,
intestines, red blood cells and kidneys becomes relatively smaller with
increase in total weight. This means that above a certain point the organs
would not be able to handle the metabolic requirements of such a gargantuan
body, but the problems of food supply would probably set a limit on further
growth long before that point is reached.

[psr]

hang on...I'm sure I've got a dictionary round here somewhere........

Now why couldn't that info have been easily accessible for me when I was doing my science degree?????? No wonder I never finished it!!

psr

Isn't this a little bit like asking why ants are so small? Not poking fun but when you look at the massive diversity of life on earth there's bound to be something at some point in time which just happens to be much bigger than everything else! There are many unanswerable questions, I mean, why do kangaroos bounce along like springs when everything else seems to get along much better on four legs? If insects can avoid flying into most things then why do they have such a problem with cars? Maybe its the highly reflective surface???

[psr]

Funky,

I like you. You seem like a smarta***!!!! In a nice kind of way!

psr

Why thank you psr. A worthy condonation from a scientist indeed.
Whenever you read my posts please do so with tongue in cheek!