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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Plants & Animals News
September 16, 2026
Sep. 15, 2026 The flesh eating New World screwworm has returned to the United States, threatening livestock, wildlife, pets and potentially people as it spreads north. A new UC San Diego tracking system aims to predict where the parasite could strike next while ...
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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 ...
Sep. 5, 2026 Researchers at UC San Diego have demonstrated that a key cellular enzyme can accurately read an eight-letter genetic alphabet, doubling the four letters used by all known life on Earth. Detailed imaging revealed that RNA polymerase handles synthetic ...
Sep. 4, 2026 A substance found in edible sea squirts appeared to reverse several signs of aging in older mice. Plasmalogen supplements improved memory and learning, strengthened connections between brain cells, reduced inflammation, and even helped the mice grow ...
Sep. 4, 2026 Puerto Rico’s normally rainy season has instead brought a severe and fast-growing drought. By August 25, three-quarters of the territory was in at least moderate drought, with extreme drought covering 44 percent and some areas receiving less than ...
Sep. 4, 2026 MIT researchers have created bacterial “transistors” that can be wired together into living circuits capable of performing calculations and directing chemical signals. One day, these biological computers could coat plant roots or leaves, ...
Latest Headlines
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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 ...
Sep. 15, 2026 A 125-million-year-old crocodile fossil has revealed preserved skin, possible sensory organs, sophisticated respiratory structures, and an unexpected pattern on its tail. Ultraviolet light exposed ...
Sep. 14, 2026 Scientists have directly observed how two negatively charged DNA molecules can pair up despite normally repelling each other. Positively charged metal ions appear to bridge the gap, helping matching ...
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 ...
Sep. 9, 2026 Two major alien-life announcements in 2025 generated enormous excitement, but most astrobiologists remained unconvinced. Only 6.6% of surveyed experts thought possible biological molecules on K2-18b ...
Sep. 8, 2026 Researchers discovered that combinations of toxin-blocking proteins naturally found in rattlesnake blood can powerfully neutralize venom from several dangerous snake species. In lab tests, the ...
Sep. 8, 2026 Scientists have identified a giant new dinosaur from Brazil that reached about 20 meters long and lived 120 million years ago. Its surprising evolutionary ties to a Spanish dinosaur suggest its ...
Sep. 8, 2026 The extinct “American cheetah” was not really a cheetah at all, but a puma relative with an unexpectedly flexible lifestyle. Fossils from the Yukon suggest northern populations survived partly by ...
Sep. 7, 2026 A critically endangered roloway monkey has given birth just months after surgeons performed an unusual operation that saved her foot from amputation. ...
Sep. 5, 2026 A common frog found across Ecuador and Colombia has finally been recognized as its own species after more than a century of mistaken identity. Museum specimens from the 1800s helped scientists reveal ...