How have animals evolved to become special?

Why are whales so huge? Why do turtles have such long shells or necks of giraffes?

The above highlights have evolved over time to help animals adapt to life in the wild.

tortoiseshell

For many years, scientists have debated the evolution of turtle shells. According to a report published in the journal Current Biology, paleontologists once believed that the shell was formed through the fusion of bone scales, like the bone plates that make up the scales on the back of a crocodile. or armadillo.

But developmental biologists disagree with this theory because they observe that turtle embryos develop differently from crocodiles or armadillos. Instead, they believe that turtle shells evolved through a process where the ribs gradually expanded and fused across the body.

The debate heated up until 2008, when Chinese scientists discovered fossils of half-shelled turtles with teeth. Although the carapace is not complete, it does not have bony scales but has extended ribs, confirming the theory of developmental biologists. Scientists believe that the expansion of the ribs was an intermediate step in the evolution of turtle shells.

Giraffe's neck

The giraffe's neck evolved after fighting with other species.

Giraffes' necks can be up to 3 meters long, allowing them to eat leaves from tall trees. However, the ancestors of today's giraffes did not possess this impressive neck.

Scientists have found fossils of Discokeryx xiezhi, a relative of modern giraffes, which lived about 17 million years ago. This species was smaller than modern giraffes, with a short neck and a thick, disc-shaped skull.

In 2022, scientists hypothesized that D. xiezhi's thick skull had evolved to withstand strong blows to the head during fights between males. After such battles, their necks grow longer and longer to support fighting.

The winning males will pass this gene on to their descendants, creating the current giraffe breed. The losers may have died or have no mates. The above hypothesis is called 'sex-based necking'.

Size of the whale

The blue whale is currently the largest animal in the world. They evolved from their ancestor Pakicetus, which was about the size of a dog. According to a 2016 study in the journal Biology Letters, the size of whales, including blue whales, has increased significantly over the past 5.3 million years.

One of the reasons for this remarkable evolution is the whale's filtering behavior. To feed, whales move to places with a lot of plankton, open their mouths and suck in large amounts of water and bait.

They then use their bristly-like teeth to sift through food. This somewhat passive feeding strategy is associated with a highly efficient metabolism, allowing whales to conserve large amounts of energy when traveling long distances.

Scientists believe that in the past, the source of plankton, due to melting ice flowing into the ocean, was huge and rich in nutrients. Abundant food sources, combined with low energy consumption, have promoted the whales' remarkable growth and allowed them to reach their current giant size.

Tiger stripes

Stripes help tigers camouflage when catching prey.

Tigers have different stripes, like fingerprints in humans. They help tigers easily hide in the grass when hunting.

In 1952, British mathematician Alan Turing hypothesized that a chemical reaction between two heterogeneous substances was responsible for creating these 'patterns'. He called these substances 'morphogens', located in the layers of the tiger's skin.

One acts as an activator and the other as an inhibitor. The activator will create stripes on the tiger's body and the inhibitor will create spaces between the stripes.

This hypothesis was proven in 2012 in the journal Nature Genetics.

Rattlesnake

The sound of a rattlesnake's tail gives chills to anyone who hears it. According to a 2016 study in the journal The American Naturalist, scientists observed 56 species of snakes in the Viperidae family, which includes rattlesnakes, and Colubridae, one of the largest snake families.

When faced with a threat, snakes from both families begin to shake and vibrate their tails, suggesting that this behavior is something the snake family has in common. The sound emitted from a rattlesnake's tail when shaking is caused by two layers of keratin, the same material that makes up human fingernails, at the end of the tail colliding. The inside of the tail, outside the horn layer, is hollow, so the sound is more resonant and shrill.

The fastest snakes that shake their tails form a group, called rattlesnakes, which are also the most evolved species in the snake family.

Lobster claws

Lobster-like crustaceans first appeared about 400 million years ago, but their claws grew large about 200 million years later. During this period, competition for food among marine predators is increasing, requiring lobster claws to become larger and stronger.

Up to now, lobsters have two extremely large, sharp, sturdy bodies, but the sizes of both sides are not equal. The larger one is the lobster's dominant claw with fast muscle fibers, able to catch prey at a speed of 20 milliseconds. The other one is smaller but sharp and sturdy like a crusher to shred prey.

When born, a lobster's two claws are about the same size. But they change size over time to suit how they are used.