For animals, the most stressful of all the abiotic stressors is heat. This is because many species are unable to regulate their internal body temperature. Even in the species that are able to regulate their own temperature, it is not always a completely accurate system. Temperature determines metabolic rates, heart rates, and other very important factors within the bodies of animals, so an extreme temperature change can easily distress the animal’s body. Animals can respond to extreme heat, for example, through natural heat acclimation or by burrowing into the ground to find a cooler space. It is also possible to see in animals that a high genetic diversity is beneficial in providing resiliency against harsh abiotic stressors. This acts as a sort of stock room when a species is plagued by the perils of natural selection. A variety of galling insects are among the most specialized and diverse herbivores on the planet, and their extensive protections against abiotic stress factors have helped the insect in gaining that position of honor.
Monday, January 26, 2009
Abiotic stress In Animals
For animals, the most stressful of all the abiotic stressors is heat. This is because many species are unable to regulate their internal body temperature. Even in the species that are able to regulate their own temperature, it is not always a completely accurate system. Temperature determines metabolic rates, heart rates, and other very important factors within the bodies of animals, so an extreme temperature change can easily distress the animal’s body. Animals can respond to extreme heat, for example, through natural heat acclimation or by burrowing into the ground to find a cooler space. It is also possible to see in animals that a high genetic diversity is beneficial in providing resiliency against harsh abiotic stressors. This acts as a sort of stock room when a species is plagued by the perils of natural selection. A variety of galling insects are among the most specialized and diverse herbivores on the planet, and their extensive protections against abiotic stress factors have helped the insect in gaining that position of honor.
Monday, January 19, 2009
Llama
The llama (Lama glama) is a South American camelid, widely used as a pack animal by the Incas and other natives of the Andes mountains. In South America llamas are still used as beasts of burden, as well as for the production of fiber and meat.
The height of a full-grown, full-size llama is between 5.5 feet (1.6 meters) to 6 feet (1.8 m) tall at the top of the head. They can weigh between approximately 280 pounds (127 kilograms) and 450 pounds (204 kilograms). At birth, a baby llama (called a cria) can weigh between 20 pounds (9 kilograms) to 30 pounds (14 kilograms). Llamas are very social animals and like to live with other llamas as a herd. Overall, the fiber produced by a llama is very soft and is naturally lanolin free. Llamas are intelligent and can learn simple tasks after a few repetitions. When using a pack, llamas can carry about 25%–30% of their body weight for several miles.
Llamas appear to have originated from the central plains of North America about 40 million years ago. They migrated to South America and Asia about 3 million years ago. By the end of the last ice age (10,000–12,000 years ago) camelids were extinct in North America. As of 2007, there were over 7 million llamas and alpacas in South America and, due to importation from South America in the late 20th century, there are now over 100,000 llamas and 6,500–7,000 alpacas in the US and Canada.
The height of a full-grown, full-size llama is between 5.5 feet (1.6 meters) to 6 feet (1.8 m) tall at the top of the head. They can weigh between approximately 280 pounds (127 kilograms) and 450 pounds (204 kilograms). At birth, a baby llama (called a cria) can weigh between 20 pounds (9 kilograms) to 30 pounds (14 kilograms). Llamas are very social animals and like to live with other llamas as a herd. Overall, the fiber produced by a llama is very soft and is naturally lanolin free. Llamas are intelligent and can learn simple tasks after a few repetitions. When using a pack, llamas can carry about 25%–30% of their body weight for several miles.
Llamas appear to have originated from the central plains of North America about 40 million years ago. They migrated to South America and Asia about 3 million years ago. By the end of the last ice age (10,000–12,000 years ago) camelids were extinct in North America. As of 2007, there were over 7 million llamas and alpacas in South America and, due to importation from South America in the late 20th century, there are now over 100,000 llamas and 6,500–7,000 alpacas in the US and Canada.
Monday, January 12, 2009
Arctic Ocean
- Amundsen Gulf
- Baffin Bay
- Barents Sea
- Beaufort Sea
- Bering Sea
- Chukchi Sea
- Davis Strait
- Denmark Strait
- East Siberian Sea
- Greenland Sea
- Hudson Bay
- James Bay
- Kara Sea
- Kara Strait
- Labrador Sea
- Laptev Sea
- Lincoln Sea
- Norwegian Sea
- White Sea
Wednesday, January 07, 2009
Flax
Flax (is a member of the genus Linum in the family Linaceae. It is native to the region extending from the eastern Mediterranean to India and was probably first domesticated in the Fertile Crescent This is called as Jawas/Javas or Alashi in Marathi. Flax was extensively cultivated in ancient Egypt. (New Zealand flax is not related to flax, but was named after it as both plants are used to produce fibres.)
Flax is an erect annual plant growing to 1.2 m tall, with slender stems. The leaves are glaucous green, slender lanceolate, 20–40 mm long and 3 mm broad. The flowers are pure pale blue, 15–25 mm diameter, with five petals; they can also be bright red. The fruit is a round, dry capsule 5–9 mm diameter, containing several glossy brown seeds shaped like an apple pip, 4–7 mm long.
In addition to referring to the plant itself, "flax" may refer to the unspun fibres of the flax plant.
Thursday, January 01, 2009
Chicxulub crater
The Chicxulub Crater is an ancient impact crater buried underneath the Yucatán Peninsula in Mexico.Its center is located near the town of Chicxulub, after which the crater is named—as well as the rough translation of the Mayan name, "the tail of the devil."The crater is more than 180 kilometers (110 mi) in diameter, making the feature one of the largest confirmed impact structures in the world; the impacting bolide that formed the crater was at least 10 km (6 mi) in diameter.
The crater was discovered by Glen Penfield, a geophysicist who had been working in the Yucatán while looking for oil during the late 1970s. Evidence for the impact origin of the crater includes shocked quartz, a gravity anomaly, and tektites in surrounding areas. The age of the rocks and isotope analysis show that this impact structure dates from the end of the Cretaceous Period, roughly 65 million years ago. The impact associated with the crater is implicated in causing the extinction of the dinosaurs as suggested by the K–T boundary, although some critics argue that the impact was not the sole reasonand others debate whether there was a single impact or whether the Chicxulub impactor was one of several that may have struck the Earth at around the same time. Recent evidence suggests that the impactor may have been a piece of a much larger asteroid that broke up in a collision in distant space more than 160 million years ago.
The crater was discovered by Glen Penfield, a geophysicist who had been working in the Yucatán while looking for oil during the late 1970s. Evidence for the impact origin of the crater includes shocked quartz, a gravity anomaly, and tektites in surrounding areas. The age of the rocks and isotope analysis show that this impact structure dates from the end of the Cretaceous Period, roughly 65 million years ago. The impact associated with the crater is implicated in causing the extinction of the dinosaurs as suggested by the K–T boundary, although some critics argue that the impact was not the sole reasonand others debate whether there was a single impact or whether the Chicxulub impactor was one of several that may have struck the Earth at around the same time. Recent evidence suggests that the impactor may have been a piece of a much larger asteroid that broke up in a collision in distant space more than 160 million years ago.
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