Reference Terms
from Wikipedia, the free encyclopedia
Animal shell
A shell is a hard, rigid outer layer, which has evolved in a very wide variety of different animals, including mollusks, sea urchins, crustaceans, turtles and tortoises, armadillos, etc. Scientific names for this type of structure include exoskeleton, test, carapace, and peltidium.
The shells that are perhaps most familiar and most commonly encountered, both in the wild and for sale as decorative objects, are seashells, more precisely, the external shells of marine mollusks. These are usually primarily composed of calcium carbonate, in the form of calcite or aragonite crystallised out in an organic matrix. Calcium carbonate in mollusc shells can take different crystalline forms, one being nacre otherwise known as mother of pearl.
Other kinds of animal shells are made from chitin, bone and cartilage, or silica.
Related Stories
1
2
Plants & Animals News
November 20, 2025
Nov. 20, 2025 Researchers have recreated a miniature human bone marrow system that mirrors the real structure found inside our bones. The model includes the full mix of cells and signals needed for blood production and even maintains this process for weeks. It ...
Nov. 19, 2025 Massive Sargassum blooms sweeping across the Caribbean and Atlantic are fueled by a powerful nutrient partnership: phosphorus pulled to the surface by equatorial upwelling and nitrogen supplied by cyanobacteria living directly on the drifting algae. ...
Nov. 18, 2025 During years of scarce fish, African penguins crowd into the same areas as commercial fishing vessels, heightening competition for dwindling prey. A new metric called “overlap intensity” shows how many penguins are affected and is already ...
Nov. 18, 2025 Scientists are turning venom, radioisotopes, engineered proteins, and AI into powerful new tools against cancer. From Amazonian scorpions yielding molecules that kill breast cancer cells as effectively as chemotherapy, to improved fibrin sealants ...
Nov. 17, 2025 Scientists mapped the Bas63 bacteriophage in unprecedented detail, uncovering how its tail machinery infects bacteria. The structure reveals rare whisker-collar features and distant evolutionary ties reaching back billions of years. These insights ...
Nov. 17, 2025 Across the planet, animals are increasingly suffering from chronic illnesses once seen only in humans. Cats, dogs, cows, and even marine life are facing rising rates of cancer, diabetes, arthritis, and obesity — diseases tied to the same factors ...
Nov. 15, 2025 Scientists discovered that a week of full submergence is enough to kill most rice plants, making flooding a far greater threat than previously understood. Intensifying extreme rainfall events may amplify these losses unless vulnerable regions adopt ...
Nov. 14, 2025 Scientists studying aging found that sensory inputs like touch and smell can cancel out the lifespan-boosting effects of dietary restriction by suppressing the key longevity gene fmo-2. When overactivated, the gene makes worms oddly indifferent to ...
Nov. 13, 2025 Researchers discovered that living horsetails act like natural distillation towers, producing bizarre oxygen isotope signatures more extreme than anything previously recorded on Earth—sometimes resembling meteorite water. By tracing these isotopic ...
Nov. 11, 2025 Scientists at EPFL have unraveled the mystery behind why biological nanopores, tiny molecular holes used in both nature and biotechnology, sometimes behave unpredictably. By experimenting with engineered versions of the bacterial pore aerolysin, ...
Nov. 10, 2025 Scientists have turned to advanced AI to decode the intricate ecosystem of gut bacteria and their chemical signals. Using a Bayesian neural network called VBayesMM, researchers can now identify genuine biological links rather than random ...
Nov. 9, 2025 A Japanese-led research team has developed AUN, a groundbreaking immune-independent bacterial cancer therapy that uses two harmonized bacteria to destroy tumors even in patients with weakened immune systems. By leveraging the natural synergy between ...
Latest Headlines
updated 12:56 pm ET
Nov. 19, 2025 Chameleons’ extraordinary ability to move their eyes independently stems from a previously overlooked anatomical marvel: long, tightly coiled optic nerves hidden behind their bulging eyes. Modern ...
Nov. 18, 2025 Researchers have discovered chemical traces of life in rocks older than 3.3 billion years, offering a rare look at Earth’s earliest biology. By combining advanced chemical methods with artificial ...
Nov. 18, 2025 Scientists have revealed that Hawaiian monk seals produce far more underwater vocalizations than previously believed. Their newly discovered 25-call repertoire includes complex combinations and a ...
Nov. 17, 2025 Hawaiian short-finned pilot whales are surprisingly voracious hunters, diving hundreds of meters beneath the Pacific to snatch squid in the dark. By tagging and tracking eight whales, researchers ...
Nov. 16, 2025 Chimps may revise their beliefs in surprisingly human-like ways. Experiments showed they switched choices when presented with stronger clues, demonstrating flexible reasoning. Computational modeling ...
Nov. 15, 2025 Researchers have sequenced the oldest RNA ever recovered, taken from a woolly mammoth frozen for nearly 40,000 years. The RNA reveals which genes were active in its tissues, offering a rare glimpse ...
Nov. 15, 2025 Scientists uncovered Australia’s oldest known crocodile eggshells, revealing the secret lives of ancient mekosuchine crocodiles that once dominated inland ecosystems. These crocs filled surprising ...
Nov. 13, 2025 Bumble bees battling invasive Argentine ants may win individual fights but ultimately lose valuable foraging time, putting pressure on colonies already strained by habitat loss, disease, and ...
Nov. 12, 2025 Scientists have identified a new crocodile precursor that looked deceptively dinosaur-like and hunted with speed and precision. Named Tainrakuasuchus bellator, the armored “warrior” lived 240 ...
Nov. 12, 2025 Over 500 million years ago, the Cambrian Period sparked an explosion of skeletal creativity. Salterella, a peculiar fossil, defied conventions by combining two different mineral-building methods. ...