Reference Terms
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Egg (biology)
In most birds and reptiles, an egg is the zygote, resulting from fertilization of the ovum. It nourishes and protects the embryo. Oviparous animals are animals that lay eggs, with little or no other development within the mother. This is the reproductive method of many fish, amphibians and reptiles, all birds, the monotremes, and most insects and arachnids.
Reptile eggs, bird eggs, and monotreme eggs, which are laid out of water, are surrounded by a protective shell, either flexible or inflexible.
The 1.5 kg ostrich egg contains the largest existing single cell currently known, though the extinct Aepyornis and some dinosaurs had larger eggs. The bee hummingbird produces the smallest known bird egg, which weighs half a gram. The eggs laid by some reptiles and most fish are even smaller, and those of insects and other invertebrates are much smaller still. The study or collecting of eggs, particularly bird eggs, is called oology.
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September 22, 2026
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Sep. 17, 2026 Scientists discovered a new frog species in the flooded forests of the western Amazon, distinguishing it from nearly identical relatives through DNA and its unique call. Adenomera varcena highlights how much Amazonian biodiversity remains hidden ...
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Sep. 14, 2026 More than 60 years after surveys suggested a deep coral reef off Benin was probably dead, scientists have found it alive. Cameras revealed healthy-looking coral patches supporting multiple fish species more than 50 meters beneath the surface. The ...
Sep. 14, 2026 Captive-raised saltwater crocodiles released into Bangladesh’s Sundarbans surprised scientists by settling into the wild rather than trying to return to their breeding facility. The result suggests that releasing larger, mature captive crocodiles ...
Sep. 13, 2026 Scientists have engineered yeast to turn PET plastic and agricultural waste into ingredients for protein-rich, 3D-printed cookies called µBites. Developed partly for NASA’s Deep Space Food Challenge, the system can produce proteins, fats, ...
Sep. 11, 2026 Long-lived bats appear to combine powerful immune defenses with unusual strategies for eliminating damaged cells, potentially helping them avoid cancer and disease for decades. Researchers hope these genetic tricks could eventually reveal new ways ...
Sep. 11, 2026 Britain’s wasps have become mysteriously scarce this summer, and scientists suspect an unusual combination of temperature swings, heatwaves, and food shortages may be responsible. Even the wasps that remain appear unusually small, potentially ...
Sep. 9, 2026 Insects quietly hold much of the natural world together, yet conservation efforts are overlooking the tropical regions where more than 80 percent of insect species live. Monash University researchers ...
Sep. 7, 2026 Scientists have found evidence that some gut bacterial populations can spread rapidly between people and across continents, suggesting the microbiome may be more transmissible than previously thought. The research also revealed hidden bacterial ...
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Sep. 22, 2026 Researchers observed a humpback whale mother staying beside her presumed stillborn calf for hours and possibly days off Australia’s Gold Coast. She maintained eye contact and remained close to the ...
Sep. 20, 2026 Cats may identify one another through a surprisingly durable chemical “calling card” made from 13 unusual fatty acids in their urine. The compounds appear linked to mysterious fat droplets in the ...
Sep. 20, 2026 Chemical clues preserved inside fossilized T. rex teeth reveal that the dinosaur maintained a body temperature of about 97 degrees Fahrenheit, almost identical to humans. The finding provides direct ...
Sep. 19, 2026 A chemical that stops drywood termites from building new exoskeletons killed about 95% of colonies in testing, offering a potentially safer alternative to traditional fumigation. Because termites ...
Sep. 18, 2026 A 150-million-year-old dinosaur fossil from Spain has been identified as the first confirmed Diplodocus ever found outside North America. The giant sauropod measured about 25 meters long and was ...
Sep. 18, 2026 A newly discovered snake from New Guinea has been named after Guns N’ Roses guitarist Slash, who has loved reptiles since childhood. Genetic testing and physical differences confirmed that the ...
Sep. 16, 2026 A newly identified 240-million-year-old animal from Tanzania is forcing scientists to rethink the early dinosaur timeline. Dinodontosaurus isiyavamanda belongs to a group previously known only from ...
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Sep. 11, 2026 A feather discovered inside 66-million-year-old fossilized dinosaur poop may help explain why modern birds survived the asteroid catastrophe. The ...