Blue whales are the largest animals on Earth but feed on the smallest krill.

The largest blue whale witnessed by humans was over 30 meters long and weighed 180 tons. Its heart is as big as a car and its huge mouth can hold up to 50 people.

A newborn whale is heavier than an adult elephant, it needs to drink 400 liters of breast milk a day and can gain up to 90 kilograms in a day and night. There are many kinds of whales. Generally, they can be divided into two groups: baleen whales, which have no teeth, and toothed whales, which have sharp teeth.

Baleen whales hunt in a very specific way, in the Southern Ocean, where krill congregate, and when they swim in the ocean, they open their mouths and swallow seawater along with krill fish.

Toothed whales eat mainly large fish and marine animals. Killer whales, for example, feed on seals and walruses.

How is it that whales can grow so large that no other creature on Earth can keep up with them?

The first adventurous sea creatures landed on land 365 million years ago, and after a long period of evolution, mammals came into being. After the extinction of the dinosaurs 65 million years ago, the red whale, the ancestor of the whale, made an unexpected return to its ocean home at a critical time when mammals were about to flourish.

Fossilized red whales discovered by Philip Gingrich show that they lived most of their lives in the ocean. Although they can stay on land for short periods, their hind legs are shorter and smaller, near the sides of their bodies. At this time, their spines became freer and looser, allowing them to move up and down like modern whales, which helped their horizontal tail lobes hit the surface of the water efficiently, facilitating the forward movement of their bodies.

Is this sudden evolution of whales intrinsically linked to their genetics and body size?

Modern science has proven that the size and lifespan of an organism are determined by genetic and environmental factors. Whales can grow to hundreds of tons because the buoyancy of seawater greatly offsets the weight problems associated with their immense size, and the whales' unique genetics make them the largest marine mammals on Earth. Philip Gingrich says the main thing that determined the return of whale ancestors to the ocean was food. This is similar to how our human ancestors had to come to the land in search of food after eating the fruit from the trees.

Gingrich added, "Interestingly, food selection played a big role in the evolution of whales. Baleen whales that eat only krill fish are much larger, such as blue whales and humpback whales, while toothed whales such as killer whales are much smaller, and zigzagging hunts sap some of their energy, making it unlikely that they will grow too big."