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How does our vision compare to some animals?
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Do animals see the same way we do? Do some animals have better vision than humans? The senses of animals have evolved to give members of the species an optimum chance for survival. Here are a few examples: Some animals, such as cats, have a reflective surface ( tapetum) on the back of the eye behind the sensory receptors (left image above). When light first enters the eye, some light is detected by the sensory receptors. The light not detected by the sensory receptors continues onto the reflective surface at the back of the eye. This light is then reflected outward toward the sensory receptors, providing a second opportunity for detection. This feature produces two results. First, the outward reflection results in the shining of the cat's ey ...
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14940 |
Biology Forums |
A year ago |
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2 |
14730 |
bio_man |
11 years ago |
The science of fireworks
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Many of us around the world will enjoy a firework display tonight (or have already); but what are the mechanisms behind the magnificent spectacle?The story behind fireworks begins about 2000 years ago in China. Alchemists at the time were in search for an elixir which made them immortal. Obviously, they did not find this- what they did find however was a substance consisting of potassium nitrate, charcoal and suphur; or gunpowder,as we know it. The evolution of fireworks from gunpowder took another 1000 years until a monk named Li Tian realised that if you placed gunpowder into a bamboo tube and ignited it, an impressive explosion on sound and light ensued. Fireworks were born! The gunpowder is responsible for the trajectory of the firework, ...
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15897 |
bio_man |
11 years ago |
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5988 |
bio_man |
11 years ago |
Sunda pangolins
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Sunda pangolins have become the most frequently seized mammal in the illegal wildlife trade in Asia, as smugglers sell the creatures to meet culinary and medicinal demand. These gentle insectivores are now on the endangered species list.
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6505 |
bio_man |
11 years ago |
What really causes an 'ice age'?
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I learned about something called axial precession in astronomy class several years ago, which is the idea that as something rotates along its axis, it will slowly trace out a cone if the weight of the object isn't equally distributed. In the case of Earth, Earth isn't a perfect sphere as many of us may think it is -- it actually bulges out in the middle enough for it to allow this phenomenon to occur. At the time, all I really took from this concept was how fascinating it is for the north axial pole to move 1° every 72 years from where it is now, and complete one full cycle every 26 000 years. However, I never managed to understand how this concept could fit in to my understanding of why ice ages [1] occur, and why they too follow a specific ...
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2765 |
bio_man |
11 years ago |
The mammoth of birds
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This bird, known as the elephant bird, went extinct sometime in the 17th century as a result of human activity. Although flightless, the birds were widespread, inhabiting the northern to the southern tip of Madagascar. Not only are they three times the size of an ostrich, they are also known for their massive egg. These fossils are so rare that one is currently being auctioned and is expecting to go for an upwards cost of $40 000..
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3842 |
bio_man |
11 years ago |
Stealth bomber
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This is the Northrop Grumman B-2 Spirit (stealth bomber). This machine is capable of pin-point strikes on most any hardened target available such as underground bunkers. Needless to say, it is also capable of delivering nuclear weapons. This stealthy aircraft was designed in a way that enemies could not anticipate its arrival, but its 22,600 Kg bomb load and a multitude of nuclear missiles would ensure they'd know when it had arrived. Named the B-2 Spirit, its advantage in battle is derived from its designation spirit; it operates like a ghost. Engines: Four General Electric F118-GE-100 turbofans of 17,300 lbs. thrust each Wingspan: 172 ft. Length: 69 ft. Height: 17 ft. Speed: High subsonic Takeoff weight: 336,500 lbs. ...
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3836 |
bio_man |
11 years ago |
Earliest form of contraception
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If you were to guess, what do you think ancient humans used as contraceptives? It's definitely hard to list even a couple of ideas given how far we've come since the start of the 20th century. According to historians, the first-known contraceptive was crocodile dung, used in Egypt in 2000 BC. Dried dung was inserted into the vagina to form an impenetrable barrier. Other pessaries used back in the day included tree sap, lemon halves, cotton, wool, sea sponges, and elephant dung. Later on, however, condoms made of animal bladders or intestines were also reportedly used. Luckily, in 1844, Charles Goodyear obtained the first patent for a rubber condom. ...
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4022 |
bio_man |
5 years ago |
A monster of an ant
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The bullet ant, or Paraponera clavata, lives throughout Central and South America. What makes this ant a formidable insect are its large mandibles and stinger. The bullet ant is one of the largest ants, growing to a length of just under 1 inch. Most notable about the ant is its ability to produce an excruciating sting.
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3282 |
bio_man |
10 years ago |
What accounts for blue blood found in invertebrates
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Hemocyanins are proteins that transport oxygen throughout the bodies of some invertebrate animals. These metalloproteins contain two copper atoms that reversibly bind a single oxygen molecule (O 2). They are second only to hemoglobin in frequency of use as an oxygen transport molecule. Unlike the hemoglobin in red blood cells found in vertebrates, hemocyanins are not bound to blood cells but are instead suspended directly in the hemolymph. Oxygenation causes a color change between the colorless Cu(I) deoxygenated form and the blue Cu(II) oxygenated form. ...
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5245 |
bio_man |
10 years ago |
Birthmarks and what causes them
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Birthmarks are congenital marks on the skin that appear at birth and occasionally disappears spontaneously. The term nevus refers to a benign cutaneous tumor consisting of blood capillaries. Such tumors, which rarely spread from their original site and are not dangerous, vary in color according to whether the capillaries composing them carry arterial or venous blood. The popularly termed cherry marks and port-wine stains (shown below) are nevi on a level with the surface of the skin. Certain other vascular nevi, commonly known as strawberry or raspberry marks (scientifically known as hemangiomas), are slightly elevated above the surface. These can appear anywhere on the body's surface, including the airway within the nose. The former Soviet ...
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5146 |
bio_man |
2 years ago |
The Twisted Relationship Between American Cockroaches and Jewel Wasps
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Nature is a stage where astonishing dramas unfold, showcasing the intricate web of relationships between diverse organisms. One such mesmerizing tale is the peculiar association between the American cockroach ( Periplaneta americana) and the jewel wasp ( Ampulex compressa). The relationship between these two species is unique and fascinating. The female jewel wasp wasp has a specialized predatory behavior that involves using American cockroaches as hosts for their offspring. The wasp targets the American cockroach as a living nursery for its developing young. It does so by injecting a venomous sting into specific parts of the cockroach's nervous system, temporarily paralyzing its front legs. Once the cockroach is immobilized, the wasp leads it ...
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1595 |
bio_man |
9 months ago |
The staircase that defies science
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The Loretto staircase – built within the Loretto Chapel in New Mexico, USA – is by far the most remarkable staircase ever built. It features a double-helical spiral structure that spans 20 feet in altitude, and remains intact without the use of a central pole. The staircase is built mostly out of wood and is held together by wooden pegs and glue rather than nails or other hardware. The staircase is venerated by Catholics as being miraculous, not due to its marvel, but based on the events that have been passed down by the Sisters of chapel ever since it was built in the late 1800s. Before the construction of the Chapel could be completed, the architect responsible for the building's design had suddenly died, leaving the nuns without access to ...
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5629 |
bio_man |
2 years ago |
This Island has More Sheep than Humans
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The Falkland Islands is an archipelago (meaning a cluster of smaller islands) in the South Atlantic Ocean, 300 miles (483 kilometres) east of Argentina. The 700+ islands have a combined area of 4,700 square miles (12,000 square kilometers), with a population of approximately 4,500 people. The Islands economy is largely based on sheep farming, with an emphasis on high-quality wool exports. The current sheep population scattered throughout the land exceeds 500,000, which equates to roughly 111 sheep per person; per capita, that's 106 sheep per square mile (41.6 per square kilometer). Since the Islands are located north of Antarctica, sheep farming had to have been introduced at some point in history. Early settlers who were of British origin ...
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4081 |
bio_man |
4 years ago |
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