Life first appeared in Earth's primordial seas some 3.6 billion years ago and evolved into a wide diversity of marine and terrestrial creatures before dinosaurs arose. Unicellular organisms, echinoderms, mollusks, insects, arachnids, crustaceans, fish, sharks, mosses, ferns, conifers, amphibians and many reptiles appeared before the dinosaurs and continue to evolve today.
Dinosaurs ruled our planet throughout the Mesozoic, which stretched from 225 to 65 million years ago (MYA), but other life forms also arose during that Era. Turtles, crocodilians and the earliest mammals appeared in the Triassic Period (225-190 MYA), ancestral birds and flowering plants graced the Jurassic Period (190-135 MYA) and the Cretaceous Period (135-65 MYA) witnessed the rise of ants, social bees, snakes, marsupials and the first deciduous trees.
Since the end of the Mesozoic (65 MYA), when dinosaurs became extinct, these "terrible lizards" live on as birds and Earth's mammals have exploded in number and variety. Primates, bats, cetaceans, manatees, rodents, canids, felines, ruminants, horses and essentially all of our modern mammals arose after the Age of Dinosaurs. Hominids have walked the Earth for no more than 6 million years and the human species is less than 150,000 years old.
Selasa, 07 Desember 2010
Senin, 06 Desember 2010
Eastern White Pines
It is during the winter, when the deciduous trees are bare, that we pay most attention to the conifers. But, since I park by pickup beneath a large white pine at our Columbia home, I find it hard to ignore this tree in any season. In spring, its small staminate flowers release a copious amount of yellow pollen which coats the truck; soon thereafter the spongy flowers begin to fall, collecting in the bed or along the base of the windshield. Drops of pine sap leave sticky residue on the hood throughout the year and heaps of yellowing pine needles surround the pickup in mid autumn.
Eastern white pines, the largest conifers in eastern North America, are native to southern Canada, New England, Pennsylvania, and the Great Lake States, extending southward along the Appalachian chain. Widely planted as ornamentals, these stately trees were once used for sail masts and are now harvested for lumber or used as Christmas trees. Often growing up to 100 feet tall and possessing a girth that may exceed 10-15 feet, some white pines in virgin stands exceed 200 feet in height. Those that escape browsing, disease or human harvesting may live for 250 years and a few specimens are known to be nearly 500 years old.
Due to their relatively long needles (bundled in groups of 5) and the open spacing of their limbs, eastern white pines have an airy appearance. Their 6-inch cones peak in number every 3-5 years and bear seeds that are favored by tree squirrels, pine siskins, nuthatches, crossbills and a variety of finches. Moderately resistant to fire, white pines often form extensive stands in undisturbed areas, overgrowing and shading out their smaller deciduous neighbors. My pickup truck and I can certainly vouch for their rapid growth and prolific nature!
Eastern white pines, the largest conifers in eastern North America, are native to southern Canada, New England, Pennsylvania, and the Great Lake States, extending southward along the Appalachian chain. Widely planted as ornamentals, these stately trees were once used for sail masts and are now harvested for lumber or used as Christmas trees. Often growing up to 100 feet tall and possessing a girth that may exceed 10-15 feet, some white pines in virgin stands exceed 200 feet in height. Those that escape browsing, disease or human harvesting may live for 250 years and a few specimens are known to be nearly 500 years old.
Due to their relatively long needles (bundled in groups of 5) and the open spacing of their limbs, eastern white pines have an airy appearance. Their 6-inch cones peak in number every 3-5 years and bear seeds that are favored by tree squirrels, pine siskins, nuthatches, crossbills and a variety of finches. Moderately resistant to fire, white pines often form extensive stands in undisturbed areas, overgrowing and shading out their smaller deciduous neighbors. My pickup truck and I can certainly vouch for their rapid growth and prolific nature!
Minggu, 05 Desember 2010
Evolution of the Sonoran Desert
The Sonoran Desert of the Southwest U.S. and Northwest Mexico is a product of its latitude, the global climate and the regional topography. Lying along one of the desert bands (which run just north and just south of the Tropics), this arid ecosystem receives copious sunshine and is subjected to prolonged periods of high pressure, below which the air is sinking. This atmospheric condition retards cloud formation and both warms and dries the air as it plummets toward the Earth's surface.
Covering a broad basin and surrounded by highlands, the Sonoran Desert is shielded from moisture in all directions; to the northwest are the Sierra Nevada Mountains and the high Mojave Desert, to the north and east is the Mogollon Rim of the Colorado Plateau, to the southeast is the wall of the Sierra Madre Range and, to the southwest, are the mountains of Southern California and the Baja Peninsula. Any air that enters the Sonoran is thus downsloping from higher terrain, causing it to heat up and dry out even further. Since the mountains and plateaus that surround it were uplifted within the past 4 to 20 million years (during the Miocene and Pliocene), the Sonoran Desert is one of the youngest ecosystems on our planet.
Throughout the Pleistocene and into the Holocene, Earth's climate has undergone dramatic shifts. When the climate cooled and glaciers advanced, the area of the Sonoran Desert decreased; in contrast, when the climate warmed (as it has done over the past 10,000 years), the Desert advanced, climbing onto the walls of the adjacent highlands. Throughout these gyrations, the regional flora and fauna have evolved, developing traits that enhanced survival in an arid environment with intense sunshine, cool nights and seasonal rains.
Covering a broad basin and surrounded by highlands, the Sonoran Desert is shielded from moisture in all directions; to the northwest are the Sierra Nevada Mountains and the high Mojave Desert, to the north and east is the Mogollon Rim of the Colorado Plateau, to the southeast is the wall of the Sierra Madre Range and, to the southwest, are the mountains of Southern California and the Baja Peninsula. Any air that enters the Sonoran is thus downsloping from higher terrain, causing it to heat up and dry out even further. Since the mountains and plateaus that surround it were uplifted within the past 4 to 20 million years (during the Miocene and Pliocene), the Sonoran Desert is one of the youngest ecosystems on our planet.
Throughout the Pleistocene and into the Holocene, Earth's climate has undergone dramatic shifts. When the climate cooled and glaciers advanced, the area of the Sonoran Desert decreased; in contrast, when the climate warmed (as it has done over the past 10,000 years), the Desert advanced, climbing onto the walls of the adjacent highlands. Throughout these gyrations, the regional flora and fauna have evolved, developing traits that enhanced survival in an arid environment with intense sunshine, cool nights and seasonal rains.
Sabtu, 04 Desember 2010
Madagascar and its Primates
As Pangea continued to break apart, Madagascar split from Africa, some 160 million years ago. Drifting to the south, it merged with the remnants of Gondwanaland, the combined mass of Antarctica, India and Australia. There, its African flora and fauna mingled with the plants and animals of that tropical land mass. About 95 million years ago, the India-Madagascar segment broke from Antarctica-Australia, moving to the northeast; within another 15 million years, Madagascar began to rift from India, presumably triggered by an underlying hotspot that also produced the massive Deccan Traps basalt flow at the end of the Mesozoic. By 70 million years ago, Madagascar was moving into prolonged isolation and now rests 350 miles off the southeast coast of Africa.
While the earliest mammals arose during the Triassic, more than 200 million years ago, primates first appeared late in the Cretaceous, after Madagascar had become an isolated land mass. About 60 million years ago, these ancestral primates split into the prosimian line (which led to lemurs, lorises, galagos and pottos) and the anthrapoid line (leading to monkeys, apes and hominids). Spreading across the globe these two groups shared similar habitats and, over time, the anthrapoids were more successful, pushing the prosimians toward extinction.
According to current scientific theory, ancestral lemurs reached Madagascar on rafts of vegetation, torn from the African coast by seasonal storms. There, free from anthrapoid competition, they have flourished and, today, are represented by more than 100 species and subspecies. A second primate, humans, reached Madagascar by boat, colonizing the Earth's fourth largest island about 2000 years ago. Unfortunately, the Malagasy and their descendents have since destroyed much of the natural habitat; lemurs and other Madagascar animals, 80% of which are endemic to the island, are increasingly threatened by deforestation and other human activity.
While the earliest mammals arose during the Triassic, more than 200 million years ago, primates first appeared late in the Cretaceous, after Madagascar had become an isolated land mass. About 60 million years ago, these ancestral primates split into the prosimian line (which led to lemurs, lorises, galagos and pottos) and the anthrapoid line (leading to monkeys, apes and hominids). Spreading across the globe these two groups shared similar habitats and, over time, the anthrapoids were more successful, pushing the prosimians toward extinction.
According to current scientific theory, ancestral lemurs reached Madagascar on rafts of vegetation, torn from the African coast by seasonal storms. There, free from anthrapoid competition, they have flourished and, today, are represented by more than 100 species and subspecies. A second primate, humans, reached Madagascar by boat, colonizing the Earth's fourth largest island about 2000 years ago. Unfortunately, the Malagasy and their descendents have since destroyed much of the natural habitat; lemurs and other Madagascar animals, 80% of which are endemic to the island, are increasingly threatened by deforestation and other human activity.
Jumat, 03 Desember 2010
The Voice of Winter
Winter is the quiet season. Compared with the rest of the year, there are relatively few natural sounds that greet us on our excursions through the fields and woodlands. Of course, exceptions do exist: the crunch of snow beneath our boots, the rattling of limbs in the winter wind, the rustling of dead oak leaves and the dreaded sound of sleet, coating our cars and walkways. The wild creatures chime in now and then: the howl of coyotes, the eerie bark of fox, the cheerful tune of chickadees, the drumming of woodpeckers and the raucous cries of jays and crows come to mind. But, for me, the voice of winter is the gruff call of the great horned owl.
Oblivious to the ice, snow and frigid air and well equipped to stalk the long, dark nights, this large and powerful predator symbolizes the harsh winter season and epitomizes the survival skills that it demands. Hidden from view for much of the day, great horned owls appear along wood borders in the gathering dusk, ready for a night of hunting. They have a distinct advantage during the barren months of winter, ensuring good health for their breeding season, which will commence by January.
Ominous to many, their deep, echoing hoots inspire those of us who appreciate the hardiness and stamina of our wild winter residents. It is understandable that mice, cottontails and other small mammals may not share that appreciation.
Oblivious to the ice, snow and frigid air and well equipped to stalk the long, dark nights, this large and powerful predator symbolizes the harsh winter season and epitomizes the survival skills that it demands. Hidden from view for much of the day, great horned owls appear along wood borders in the gathering dusk, ready for a night of hunting. They have a distinct advantage during the barren months of winter, ensuring good health for their breeding season, which will commence by January.
Ominous to many, their deep, echoing hoots inspire those of us who appreciate the hardiness and stamina of our wild winter residents. It is understandable that mice, cottontails and other small mammals may not share that appreciation.
Kamis, 02 Desember 2010
The Benefits of Aging
Aging has its disadvantages. Our physical strength and stamina tend to deteriorate, we are more prone to a variety of illnesses and, for some, our mental faculties begin to fail. When we reach middle age, we begin to notice the early signs of aging and, combined with the other stressors of that period, this observation can induce a sense of resignation and cause some to give up on the joys of life.
But those who remain active, both physically and mentally, come to realize that there are also benefits of growing older. For most of us, the responsibilities of our career and our family life begin to disipate and we have more time to engage in exercise, hobbies and other personal interests. Those endowed with creativity are especially rewarded by this age-induced freedom; indeed, history is replete with famous writers, painters, photographers and other artisans who took up their passion later in life and, possessing the experience and wisdom of advanced age, were especially productive and successful.
Whether or not you possess such talents, the decision to engage in new activities will likely benefit your physical and mental health. The process of learning a new skill exercises the brain and the body, enhancing mental function, improving coordination and inducing a sense of personal satisfaction, all of which make us less prone to illness and injury. Death is surely inevitable but growing old can have its rewards.
But those who remain active, both physically and mentally, come to realize that there are also benefits of growing older. For most of us, the responsibilities of our career and our family life begin to disipate and we have more time to engage in exercise, hobbies and other personal interests. Those endowed with creativity are especially rewarded by this age-induced freedom; indeed, history is replete with famous writers, painters, photographers and other artisans who took up their passion later in life and, possessing the experience and wisdom of advanced age, were especially productive and successful.
Whether or not you possess such talents, the decision to engage in new activities will likely benefit your physical and mental health. The process of learning a new skill exercises the brain and the body, enhancing mental function, improving coordination and inducing a sense of personal satisfaction, all of which make us less prone to illness and injury. Death is surely inevitable but growing old can have its rewards.
Rabu, 01 Desember 2010
December
A northwest wind developed yesterday afternoon, behind the latest cold front, and, overnight, ushered in the coldest air and lowest wind chill since last winter. December made its appearance beneath a frigid, clear sky, lit by a crescent moon, bright Venus and a bowl of twinkling stars. On my walk to work this morning, it was 22 degrees F.
Festooned with holiday lights and leading up to the beloved season of Christmas, December does not incite the animosity that January and February stir in the soul of tropical man. Nevertheless, in the Northern Hemisphere, December is the darkest month of the year and often brings severe winter weather. Even when relatively mild, the month heralds the long, steady descent toward the nadir of nature's year.
December 1 marks the calendar and meteorologic onset of winter which, from an astronomical point of view, begins with the winter solstice, on or about December 21. One can debate when the season officially begins but, to paraphrase a Supreme Court Justice, "we know it when we feel it" and, today, it felt like winter.
Festooned with holiday lights and leading up to the beloved season of Christmas, December does not incite the animosity that January and February stir in the soul of tropical man. Nevertheless, in the Northern Hemisphere, December is the darkest month of the year and often brings severe winter weather. Even when relatively mild, the month heralds the long, steady descent toward the nadir of nature's year.
December 1 marks the calendar and meteorologic onset of winter which, from an astronomical point of view, begins with the winter solstice, on or about December 21. One can debate when the season officially begins but, to paraphrase a Supreme Court Justice, "we know it when we feel it" and, today, it felt like winter.
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