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Why Are Eggs Egg-Shaped?

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Thinkstock

There’s only one thing in this world shaped like an egg. Not exactly spherical, not exactly an oval, it’s kind of hard to describe what an egg looks like. “Asymmetric tapered oval”? Sure, why not.

But why are eggs shaped this way? Evolution, my dear Watson. Evolution.

If eggs were perfectly spherical, they would be more likely to roll out of a nest and break. Instead, because they have a tapered end, they make a circular path when they roll. This path keeps them within the safe confines of their nests. Amazingly enough, birds that nest on cliffs have more oval-like eggs that roll in tighter circles. These eggs are even less likely to roll out of a nest and off of the cliff. Conversely, birds that nest on the ground lay eggs that are less oval-shaped.

The tapered shape of eggs also allows them to fit more snugly inside the nest and keep each other warm.

Additionally, eggs are tapered because an asymmetric tapered oval is the ideal shape for an egg to be pushed out of a hen. Eggs travel through the cloaca and emerge from a part of the anatomy called the vent located just under the tail, and because the tapered end of an egg has more surface area than the blunt end, the chicken’s muscles have an easier time squeezing it out. (Fun fact: A chicken's intestine is also connected to the vent, so hens relieve themselves and push out eggs via the same opening.)

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Animals
Where Do Birds Get Their Songs?
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iStock

Birds display some of the most impressive vocal abilities in the animal kingdom. They can be heard across great distances, mimic human speech, and even sing using distinct dialects and syntax. The most complex songs take some practice to learn, but as TED-Ed explains, the urge to sing is woven into songbirds' DNA.

Like humans, baby birds learn to communicate from their parents. Adult zebra finches will even speak in the equivalent of "baby talk" when teaching chicks their songs. After hearing the same expressions repeated so many times and trying them out firsthand, the offspring are able to use the same songs as adults.

But nurture isn't the only factor driving this behavior. Even when they grow up without any parents teaching them how to vocalize, birds will start singing on their own. These innate songs are less refined than the ones that are taught, but when they're passed down through multiple generations and shaped over time, they start to sound similar to the learned songs sung by other members of their species.

This suggests that the drive to sing as well as the specific structures of the songs themselves have been ingrained in the animals' genetic code by evolution. You can watch the full story from TED-Ed below, then head over here for a sample of the diverse songs produced by birds.

[h/t TED-Ed]

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Animals
Watch the First-Ever Footage of a Baby Dumbo Octopus
NOAA, Wikimedia Commons // Public Domain
NOAA, Wikimedia Commons // Public Domain

Dumbo octopuses are named for the elephant-ear-like fins they use to navigate the deep sea, but until recently, when and how they developed those floppy appendages were a mystery. Now, for the first time, researchers have caught a newborn Dumbo octopus on tape. As reported in the journal Current Biology, they discovered that the creatures are equipped with the fins from the moment they hatch.

Study co-author Tim Shank, a researcher at the Woods Hole Oceanographic Institution in Massachusetts, spotted the octopus in 2005. During a research expedition in the North Atlantic, one of the remotely operated vehicles he was working with collected several coral branches with something strange attached to them. It looked like a bunch of sandy-colored golf balls at first, but then he realized it was an egg sac.

He and his fellow researchers eventually classified the hatchling that emerged as a member of the genus Grimpoteuthis. In other words, it was a Dumbo octopus, though they couldn't determine the exact species. But you wouldn't need a biology degree to spot its resemblance to Disney's famous elephant, as you can see in the video below.

The octopus hatched with a set of functional fins that allowed it to swim around and hunt right away, and an MRI scan revealed fully-developed internal organs and a complex nervous system. As the researchers wrote in their study, Dumbo octopuses enter the world as "competent juveniles" ready to jump straight into adult life.

Grimpoteuthis spends its life in the deep ocean, which makes it difficult to study. Scientists hope the newly-reported findings will make it easier to identify Grimpoteuthis eggs and hatchlings for future research.

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