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Southern Gastric Brooding Frog
The Southern Gastric Brooding Frog (Rheobotrahcus silus) was a frog species that lived in Australia. It was declared extinct in 2002. Once adult males fertilized the eggs of females, the females swallowed their eggs. The stomachs of the females then functioned somewhat like wombs, protecting the eggs while they gestated. Once the eggs developed into juveniles, female frogs performed oral birth and regurgitated their young.
Format: Graphics
Subject: Organisms
"How do Embryos Assess Risk? Vibrational Cues in Predator-Induced Hatching of Red-Eyed Treefrogs" (2005), by Karen Warkentin
In 'How do Embryos Assess Risk? Vibrational Cues in Predator-Induced Hatching of Red-Eyed Treefrogs' (2005), Karen Warkentin reported on experiments she conducted to see how red-eyed treefrog embryos, Agalychnis callidryas, can distinguish between vibrations due to predator attacks and other environmental occurrences, such as storms. Though the ability of red-eyed treefrogs to alter their hatch timing had been documented, the specific cues that induce early hatching were not well understood.
Format: Articles
Subject: Experiments, Organisms
The First Successful Cloning of a Gaur (2000), by Advanced Cell Technology
The first successful cloning of a gaur in 2000 by Advanced Cell Technology involved the cells of two animals: an egg cell from a domestic cow and a skin cell from a gaur. The researchers extracted the egg cell from the ovary of the domestic cow and the skin cell from the skin of the gaur. First, the researchers performed nuclear transplantation on the egg cell of the cow, during which they removed the nucleus of the egg cell. The mitochondria of the egg cell remained intact inside the cell.
Format: Graphics
Subject: Experiments, Organisms, Reproduction
Fruit Fly Life Cycle
Fruit flies of the species Drosophila melanogaster develop from eggs to adults in eight to ten days at 25 degrees Celsius. They develop through four primary stages: egg, larva, pupa, and adult. When in the wild, female flies lay their fertilized eggs in rotting fruit or other decomposing material that can serve as food for the larvae. In the lab, fruit flies lay their fertilized eggs in a mixture of agar, molasses, cornmeal, and yeast. After roughly a day, each egg hatches into a larva.
Format: Graphics
Oviraptor philoceratops Dinosaurs
Oviraptor philoceratops was a small bird-like dinosaur that lived about seventy-five million years ago, during the late Cretaceous period. In 1923, George Olsen of the American Museum of Natural History (AMNH) in New York City, New York, discovered the first Oviraptor fossilized skeleton on top of a dinosaur egg nest in the Gobi Desert, Mongolia. Because of the close proximity of dinosaur and nest, when Henry Fairfield Osborn president of the AMNH published on the discovery, he assumed that the Oviraptor had died attempting to steal the eggs.
Format: Articles
Subject: Organisms
Study of Fossilized Massospondylus Dinosaur Embryos from South Africa (1978-2012)
In 1978, James Kitching discovered two dinosaur embryos in a road-cut talus at Roodraai (Red Bend) in Golden Gate Highlands National Park, South Africa. Kitching assigned the fossilized embryos to the species of long necked herbivores Massospondylus carinatus (longer vertebra) from the Early Jurassic period, between 200 and 183 million years ago. The embryos were partially visible but surrounded by eggshell and rock, called matrix. Kitching said that the eggs were too delicate to remove from the matrix without damage.
Format: Articles
Frog Embryo in the Blastula Stage
Illustration of the animal-vegetal gradient in Xenopus laevis ( African clawed frog) eggs after fertilization. During fertilization, the sperm s point of entry determines the future dorsal side (shaded) and ventral side (unshaded) of the embryo. The prospective ventral side of the embryo forms on the side where the sperm enters while the prospective dorsal side forms opposite the sperm s point of entry.
Format: Graphics
The Southern Gastric-Brooding Frog
The Southern Gastric-Brooding Frog (Rheobatrachus silus) was an aquatic frog that lived in south-east Australia. In 2002, the International Union for Conservation of Nature Red List declared the frog extinct, although no wild specimens had been reported since 1981. As the common name alludes to, the R.
Format: Articles
Subject: Organisms
Mitochondria
All cells that have a nucleus, including plant, animal, fungal cells, and most single-celled protists, also have mitochondria. Mitochondria are particles called organelles found outside the nucleus in a cell's cytoplasm. The main function of mitochondria is to supply energy to the cell, and therefore to the organism. The theory for how mitochondria evolved, proposed by Lynn Margulis in the twentieth century, is that they were once free-living organisms.
Format: Articles
Wolbachia
Bacteria of the genus Wolbachia are
bacteria that live within the cells of their hosts. They infect a
wide range of arthropods (insects, arachnids, and crustaceans) and
some nematodes (parasitic roundworms). Scientists estimate that
Wolbachia exist in between seventeen percent and seventy-six percent of
arthropods and nematodes. The frequency of the bacteria makes them
one of the most widespread parasites. In general, they are divided
into five groups, from A to E, depending of the species of their
Format: Articles
Subject: Organisms
Intraspecies Chimeras Produced in Laboratory Settings (1960-1975)
When cells-but not DNA-from two or more genetically distinct individuals combine to form a new individual, the result is called a chimera. Though chimeras occasionally occur in nature, scientists have produced chimeras in a laboratory setting since the 1960s. During the creation of a chimera, the DNA molecules do not exchange genetic material (recombine), unlike in sexual reproduction or in hybrid organisms, which result from genetic material exchanged between two different species. A chimera instead contains discrete cell populations with two unique sets of parental genes.
Format: Articles
“Part-Human Chimeras: Worrying the Facts, Probing the Ethics” (2007), by Françoise Baylis and Jason Scott Robert
In 2007, Françoise Baylis and Jason Scott Robert published “Part-Human Chimeras: Worrying the Facts, Probing the Ethics” in The American Journal of Bioethics. Within their article, hereafter “Part-Human Chimeras,” the authors offer corrections on “Thinking About the Human Neuron Mouse,” a report published in The American Journal of Bioethics in 2007 by Henry Greely, Mildred K. Cho, Linda F. Hogle, and Debra M. Satz, which discussed the debate on the ethics of creating part-human chimeras. Chimeras are organisms that contain two or more genetically distinct cell lines.
Format: Articles