Tag: Coloring Pages

Cells by the Numbers

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Cells are the basic unit of life—and the focus of much scientific study. They’re categorized based on whether or not they have a distinct nucleus. Prokaryotic cells, like some bacteria such as blue-green algae, don’t have distinct nuclei. Instead, their nuclear material is spread throughout the cytoplasm. Eukaryotic cells—or cells with nuclei—make up humans, animals, plants, and fungi. Here are just a few of cells’ fascinating facets.

30 Trillion

That’s about how many human cells adults have in their bodies. Males are on the higher side with about 36 trillion cells, while females average about 28 trillion cells.

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Research Organism Superheroes: Hydras

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A hydra with a branched, tubelike body and tentacles extending from the main body and branch.
A hydra captured under a microscope. Credit: iStock.

Hydras might look like they’re visitors from outer space, but they’re actually Earth-dwelling animals that can be found in fresh water, like ponds or gentle streams. The body of a hydra consists of a thin tubelike stalk that’s about an inch long with several tentacles extending from one end. Some hydras can grow an armlike extension that eventually pops off the main stem to become a new hydra.

Humans have studied hydras for hundreds of years. Antonie van Leeuwenhoek, one of the earliest known microscopists, first described them in 1703 when he looked at water samples under a microscope. You can see hydras—whose bodies are about the length of a paperclip—without them, but microscopes help researchers see their shape in better detail. Scientists commonly use hydras as research organisms because of their incredible ability to regrow lost body parts after injury through a process called regeneration.

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Research Organism Superheroes: Hawaiian Bobtail Squid

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A Hawaiian bobtail squid swimming in front of a submerged hand, appearing as if to fit into the palm of the hand.
This adult Hawaiian bobtail squid swimming in front of a submerged hand illustrates its small size. Credit: The labs of Margaret J. McFall-Ngai, Carnegie Institution for Science/California Institute of Technology, and Edward G. Ruby, California Institute of Technology.

The Hawaiian bobtail squid (Euprymna scolopes) is only about as big as a golf ball, but what it lacks in size, it makes up for in its superpower—an invisibility cloak to be exact. Thanks to its symbiotic relationship with the bioluminescent bacteria Vibrio fischeri, it’s able to seemingly disappear from its predators when swimming at night.  

These super-squid live in the shallow coastal waters in the Pacific, like those around the Hawaiian Islands. They’re nocturnal, so they hunt their prey—small shrimp and other crustaceans—at night and hide, often by burying themselves in the sand, during the day while they rest. Although Hawaiian bobtail squid live their short 3-10 month lives around one another, they generally only interact for breeding, and even then, they only reproduce once in their lifetimes and die soon after reproduction.

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Research Organism Superheroes: Fruit Flies

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A fruit fly on a yellow fruit.
Credit: iStock.

Those pesky little bugs flying around the overripe bananas in your kitchen may hold the key to understanding something new about how our bodies work. That’s right, the fruit fly (Drosophila melanogaster) is a widely used research organism in genetics because of its superpower of reproducing quickly with similar genes to people.

Researchers have been studying fruit flies for over a century for many reasons. First, they’re easy to please—just keep them at room temperature and feed them corn meal, sugar, and yeast (or those bananas on your counter!). Second, they reproduce more quickly and have shorter life cycles than larger organisms. A female can lay up to a hundred eggs in a day, and those eggs develop into mature adult flies within 10 to 12 days. A third reason is the simplicity of the fruit fly’s genome, which only has four pairs of chromosomes compared to the 23 in humans. And on a logistical note, the male and female flies are easy to tell apart (genetic studies often require separating males and females, which isn’t an easy feat in all organisms).

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Research Organism Superheroes: Tardigrades

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A brown, barrel-shaped body with rolls, eight legs, pointy claws, and a round mouth against a green background.
A 3D rendering of a tardigrade. Credit: iStock.

“Water bear” or “moss piglet”? No matter what you call them, tardigrades have secured the title of cutest invertebrate—at least in our book. They’re tiny creatures, averaging about the size of a grain of salt, so while you can spot them with the naked eye, using a microscope is the best way to see them. They earned their nickname of water bear and their official name (which comes from tardigradus, Latin for “slow walker”) because of the way they lumber slowly and deliberately on short, stubby legs.

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