First Correlation:
Observation: All natural populations have the reproductive capacity to exceed the resources required to sustain them.
Observation: Despite their enormous reproductive potential, populations do not keep increasing indefinitely in size over time. (To give a simple example, a single sea star can release 2,500,000 every year, but oceans obviously do not fill with sea stars.)
Observation: In natural environments, food supplies and other resources do not increase explosively. In fact, they remain much the same over time.
Observation: The limited availability of resources puts limits on population growth. (There is only so much water, nutrients, and growing space for a plant population; only so many plants to feed an elephant population; and so on.)
Inference: When a population outstrips the supplies of necessary resources, there must be competition among its members for the resources that are available. Because of this competition, not all of the individuals who were born will themselves survive and reproduce.
Second Correlation:
Observation: The members of a natural population show great variation in their traits, and much of the variation is passed on through generations (it has a heritable, or genetic, basis.)
Inference: Some heritable traits are more adaptive than others. They give the individual a competitive edge in surviving and reproducing.
Inference: Over the generations, there is natural selection - a measurable difference in survival and reproduction among individuals that differ from one another in one or more traits.
Inference: Thus the character of the population changes over time - it evolves - as some forms of traits increase in frequency and others decrease or disappear.
Showing posts with label charles darwin. Show all posts
Showing posts with label charles darwin. Show all posts
Sunday, July 19, 2009
Friday, June 26, 2009
1.3 Darwin's Extraordinary Explanation
Extraordinary is not a word I am using to emphasize the validity of Charles Darwin's claims, only to emphasize their eccentricity.
On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life, otherwise known as Evolution by natural selection, is the central concept of the life's work done by Charles Darwin. Concerning theory about the origin of adaptation, complexity, and diversity among Earth's living creatures. Now before I continue further, it is understood by most in the scientific community that the definition of "theory" can only be assigned to statements or mathematical equations that can be evaluated; as to confirm or dispel their validity. In the inquest to historical events, some argue that we can never "test" evolution. I agree. We can never test the past, but we can use the information provided to establish a set of correlating possibilities and develop ideas around these constructs.
An example of testing is insects and weeds. Insects and weeds acquire resistance to our insecticides and herbicides through the same process, mutation. As we humans try to poison them, evolution by natural selection transforms the population of a mosquito or thistle into a new sort of creature, less vulnerable to that particular poison. Therefore, we invent another poison, then another. It is a futile effort. Even DichloroDiphenyl Trichloroethane (DDT), with its ferocious and long-lasting effects throughout ecosystems, produced resistant houseflies within a decade of its discovery in 1939. By 1990 more than 500 species (including 114 kinds of mosquitoes) had acquired resistance to at least one pesticide. Based on these undesired results, Stephen Palumbi has commented glumly, "humans may be the world's dominant evolutionary force."
Among most forms of living creatures, evolution proceeds slowly - too slowly to be observed by a single scientist within a research lifetime. But science functions by inference, not just by direct observation, and the inferential sorts of evidence such as paleontology and biogeography are no less cogent simply because they're indirect. Still skeptics of evolutionary theory ask; can we see evolution in action? Can it be observed in the wild? Can it be measured in the laboratory?
The answer is yes. Peter and Rosemary Grant, two British-born researchers who have spent decades where Charles Darwin spent weeks, have captured a glimpse of evolution with their long-term studies of beak size among Galapagos finches. William R. Rice and George W. Salt achieved something similar in their lab, through an experiment involving 35 generations of the fruit fly Drosphila melanogaster. Richard E. Lenski and his colleagues at Michigan State University have done it too, tracking 20,000 generations of evolution in the bacterium Escherichia coli. Despite the difficulties involved in the necessary steps of speciation, Rice and Salt seem to have recorded a speciation event, or very nearly so, in their extended experiment on fruit flies. From a small stock of mated females they eventually produced two distinct fly populations adapted to different habitat conditions, which the researchers judged "incipient species."
And so we find that we can not test the past, but can evaluate the future. Which, in certain ways, is exactly what Darwin did, hence, the theories he established. Back to Darwin.
Growing up little Charles was always "well to do." His grandfather Erasmus Darwin, a physician and naturalist, was one of the first to propose that all organisms are related by descent. During his grandfather's time period, a person having a physician's practice in England found himself on the affluent side of the coin. With the resources provided, Darwin's father was a successful physician as well. At the age of eight, Charles was an enthusiastic but haphazard collector of shells. Delighting himself, seeing as he was always said to be shy, with sciences even before he really knew what he was looking at. By ten, he began focusing on the habits of insects and birds, mesmerizing himself with the life around him. At fifteen, he found schoolwork boring compared to the pursuit of hunting, fishing, and observing the natural world; something uncommon to the pursuits of most adolescence his age. In 1831, in the midst of this intellectual ferment, Charles Darwin was twenty-two years old and wondering what exactly he was to do with and in his life. Being from a wealthy family, Darwin had the means to indulge his interest.
Darwin attempted to study medicine in college. He abandoned that study after realizing he never could practice surgery on his fellow humans, given the crude and painful procedures available at the time. For a while he followed his own inclinations toward natural history. Then his father suggested that a career as a clergyman might be more to his liking and more respectable than fooling around with nature, so Darwin packed for Cambridge, where he earned a degree. As an undergraduate at Cambridge, he had studied halfheartedly toward becoming a clergyman. However, spent most of his time among faculty members with leanings toward natural history, a sector of his passion and it would be John Henslow who perceived and respected Charles' real interest. Henslow arranged for him to take part in a training expedition led by an eminent geologist. At the pivotal moment when Charles had to decide on a career, Henslow arranged that he be offered the position of ship's naturalist aboard H.M.S. Beagle.
On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life, otherwise known as Evolution by natural selection, is the central concept of the life's work done by Charles Darwin. Concerning theory about the origin of adaptation, complexity, and diversity among Earth's living creatures. Now before I continue further, it is understood by most in the scientific community that the definition of "theory" can only be assigned to statements or mathematical equations that can be evaluated; as to confirm or dispel their validity. In the inquest to historical events, some argue that we can never "test" evolution. I agree. We can never test the past, but we can use the information provided to establish a set of correlating possibilities and develop ideas around these constructs.
An example of testing is insects and weeds. Insects and weeds acquire resistance to our insecticides and herbicides through the same process, mutation. As we humans try to poison them, evolution by natural selection transforms the population of a mosquito or thistle into a new sort of creature, less vulnerable to that particular poison. Therefore, we invent another poison, then another. It is a futile effort. Even DichloroDiphenyl Trichloroethane (DDT), with its ferocious and long-lasting effects throughout ecosystems, produced resistant houseflies within a decade of its discovery in 1939. By 1990 more than 500 species (including 114 kinds of mosquitoes) had acquired resistance to at least one pesticide. Based on these undesired results, Stephen Palumbi has commented glumly, "humans may be the world's dominant evolutionary force."
Among most forms of living creatures, evolution proceeds slowly - too slowly to be observed by a single scientist within a research lifetime. But science functions by inference, not just by direct observation, and the inferential sorts of evidence such as paleontology and biogeography are no less cogent simply because they're indirect. Still skeptics of evolutionary theory ask; can we see evolution in action? Can it be observed in the wild? Can it be measured in the laboratory?
The answer is yes. Peter and Rosemary Grant, two British-born researchers who have spent decades where Charles Darwin spent weeks, have captured a glimpse of evolution with their long-term studies of beak size among Galapagos finches. William R. Rice and George W. Salt achieved something similar in their lab, through an experiment involving 35 generations of the fruit fly Drosphila melanogaster. Richard E. Lenski and his colleagues at Michigan State University have done it too, tracking 20,000 generations of evolution in the bacterium Escherichia coli. Despite the difficulties involved in the necessary steps of speciation, Rice and Salt seem to have recorded a speciation event, or very nearly so, in their extended experiment on fruit flies. From a small stock of mated females they eventually produced two distinct fly populations adapted to different habitat conditions, which the researchers judged "incipient species."
And so we find that we can not test the past, but can evaluate the future. Which, in certain ways, is exactly what Darwin did, hence, the theories he established. Back to Darwin.
Growing up little Charles was always "well to do." His grandfather Erasmus Darwin, a physician and naturalist, was one of the first to propose that all organisms are related by descent. During his grandfather's time period, a person having a physician's practice in England found himself on the affluent side of the coin. With the resources provided, Darwin's father was a successful physician as well. At the age of eight, Charles was an enthusiastic but haphazard collector of shells. Delighting himself, seeing as he was always said to be shy, with sciences even before he really knew what he was looking at. By ten, he began focusing on the habits of insects and birds, mesmerizing himself with the life around him. At fifteen, he found schoolwork boring compared to the pursuit of hunting, fishing, and observing the natural world; something uncommon to the pursuits of most adolescence his age. In 1831, in the midst of this intellectual ferment, Charles Darwin was twenty-two years old and wondering what exactly he was to do with and in his life. Being from a wealthy family, Darwin had the means to indulge his interest.
Darwin attempted to study medicine in college. He abandoned that study after realizing he never could practice surgery on his fellow humans, given the crude and painful procedures available at the time. For a while he followed his own inclinations toward natural history. Then his father suggested that a career as a clergyman might be more to his liking and more respectable than fooling around with nature, so Darwin packed for Cambridge, where he earned a degree. As an undergraduate at Cambridge, he had studied halfheartedly toward becoming a clergyman. However, spent most of his time among faculty members with leanings toward natural history, a sector of his passion and it would be John Henslow who perceived and respected Charles' real interest. Henslow arranged for him to take part in a training expedition led by an eminent geologist. At the pivotal moment when Charles had to decide on a career, Henslow arranged that he be offered the position of ship's naturalist aboard H.M.S. Beagle.
Subscribe to:
Posts (Atom)