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Sympatric speciation occurs in the absence of geographic isolation.

The explains plenty, and one reality is that women will always have a genetic investment in their offspring no matter who the fathers are. As civilizations rose and , they all had enhanced reproductive rights (many wives, harems, etc.), and many women found the situation tolerable and even attractive, although there could be coercion in the unions and there are many obvious disadvantages to being a "kept" woman. However, being a wife/concubine for an elite man usually meant a pretty good life and children being provided for. The biggest losers in such societies were non-dominant men, who had diminished procreation opportunities (and eunuchs guarded harems, for instance). With the rise of DNA testing, a repeating dynamic is seen: when one people at a higher economic level (energy use) encountered another, the women from the poorer culture bred with the men from the richer culture, and men from the poorer culture began vanishing from the gene pool. It is particularly noticeable among agriculturalist expansions into hunter-gatherer lands, such as the and from the Fertile Crescent into Europe and North Africa, and seems to be implicated in the spread of Mesoamerican farmers into the USA's Southwest. The general pattern during the Neolithic Expansion seems to have been farmers migrating to arable land and establishing agricultural communities that were surrounded by hunter-gatherers, and it seems more common that the farmer populations expanded and displaced (the men)/absorbed (the women) the hunter-gatherer population than hunter-gatherers learned agriculture. After a career of studying human migrations, Peter Bellwood had this to say about what motivated them:

Speciation tends to form clusters of biodiversity rather than continuous gradients.

In an attempt to fulfill the guidelines set forth in the discussion thread instructions I will begin by answering the following question: “As a Project Manager, what procurement management activities have you performed or experienced in the past?” Though my current position title is not a Project Manager I have been tasked with many of the procurement duties often times associated with Project Mangers....

Speciation - superbessaywriters

Speciation is not possible without some form of isolating barrier that disrupts gene flow.

Common usage of the term “evolution” is that living things in our world have come into existence through unguided naturalistic processes beginning from a primeval mass of subatomic particles and radiation, over 20 billion years ago....

I eventually realized that there were not enough to get free energy over the hump of humanity’s inertia and organized suppression. Soon after I completed in 2002, one of pupils called my writings “comprehensivist” and I did not know what he meant. I then and saw the point. My writings since then have been more consciously comprehensivist (also called “generalist”) in nature.

speciation Essay Example | Topics and Well Written Essays

The choice of procurement strategy is very important to the success of a construction project....

The first tree forests formed in the late Devonian, and bark is the great innovation that led to forming the Carboniferous’s vast coal deposits. Compared to modern trees, Carboniferous trees seemed to go overboard on bark, at least partly to discourage arthropods. Today’s trees generally contain at least four times as much wood as bark. Those early trees had about . trees dominated the Carboniferous rainforest and could grow 30 meters tall. Because it took more than a hundred million years for life to learn to break down lignin, that early lignin did not degrade via biological processes. The early Carboniferous was warm, even with a small ice cap at the South Pole, and Earth’s first rainforests appeared in the late Devonian and again proliferated in the Carboniferous. The Carboniferous lasted from about 360 mya to 300 mya and was the Golden Age of Amphibians, as the rainforest was largely global in extent and swamps abounded. Amphibians were the Carboniferous’s apex predators on land, and some reached crocodile size and acted like them.

Trees first appeared during a plant diversity crisis, and the arrival of seed plants and ferns ended the dominance of the first trees, so the plant crises may have been more about evolutionary experiments than environmental conditions, although a carbon dioxide crash and ice age conditions would have impacted photosynthesizers. The that gave rise to trees and seed plants largely went extinct at the Devonian’s end. But what might have been the most dramatic extinction, as far as humans are concerned, was the impact on land vertebrates. During the about 20% of all families, 50% of all genera, and 70% of all species disappeared forever.

Darwin said that evolution took place by a process of natural selection or survival of the fittest.
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Speciation Of Lake Malawis Cichlid Fish Populations Biology Essay

But even though they were “regular” on the geologic time scale, driven by , there would have been nothing “regular” about them to evolving humans. When ice sheets advanced, global climate became cooler and dryer; rainforests shrank and deserts expanded. Human adaptations to those changes, which could even be discerned in one human lifetime, must have had profound impacts on the human journey. In short, humans had to readily adapt to rapidly changing conditions, and rapid adaptation would have had selective effects on burgeoning human intelligence and problem-solving ability; those that adapted, survived. Also, scientists think that the rapidly oscillating climate resulted in migrations and pockets of isolated members of species that then underwent rapid evolutionary adaptation, the kind that leads to speciation. This may have been partly responsible for the relatively rapid evolution of the human line, particularly in the past million years.

Speciation - Free Essay Examples and Research Papers

The energy from controlled fire allowed humans to , , and socially organize in new ways. Humans commandeered energy that otherwise and used it for immediate human benefit. It was also the first great human robbery. All heterotrophs “” energy from other life forms to live. The primary exception is the symbiosis that . But no animal had ever robbed energy from ecosystems on that scale before. By making fires, humans were liberating many times the energy that their biological processes used - energy that could have fed forest ecosystems. While humans were only using deadwood, it was the least destructive to forest ecosystems. But when humans began burning forests to flush out animals to kill and make biomes suitable for animals to hunt, they were destroying and altering ecosystems on a vast scale. A cord of wood provides about four years of the calories that fuel a human adult’s body, and one hectare can provide a sustainable annual harvest of about ten years of human calories. A family of four using a hectare for firewood on a sustainable basis would be using more than twice their caloric intake for burning wood. Very little of that released energy would benefit humans if they burned it over a campfire, as humans did for the entire epoch of the hunter-gatherer; that liberated energy largely went straight into the sky. The direct benefit to humans would be the energy that went into cooking food, what warmed human flesh, what was used to make tools, and the benefits of scaring off predators and providing light at night. More indirect benefits would have been ecosystem changes to provide human-digestible calories, such as American Indians burning the woodlands and plains to make environments conducive to animals that they could easily hunt. In , the earliest epochs are the most uncertain, but saying that hunter-gatherer humans used 2.5 times their dietary calories in their economy is probably, perhaps greatly, understating the case. That 5% efficiency number is also a rough estimate, and both numbers could be refined by a scientifically performed effort. Maybe somebody has already done it. The numbers in that table for subsequent epochs are more accurate, and the most accurate of all are those for , and I live in one. The increases in efficiency became more modest with each epoch as the limits of were approached.

SparkNotes: Speciation: Types of Speciation

What is fire? That may seem too-elementary a question, but understanding what it is and where it came from is vitally important for understanding the human journey. The first fires were the quick release of stored sunlight energy that life forms, plants in that instance, had used to build themselves as they made their “decisions,” and it was from vegetation that recently died and was dry enough to burn. The energy was released from burning so fast that it became far hotter (because the molecules were violently "pushed" by the reaction that also released photons) than the biological process of making animals warm-blooded. Hot enough in fact that the released photons' (energetic enough) so that human eyes could see them, in a phenomenon called flames. Flames are visible side-effects of that intense energy release. The rapid movement of the molecules as they rocketed due to that great release of energy is the motion that powers the industrial age. Those rocketing molecules move pistons in automobile engines and , and are behind the damaging explosions of bombs and the propulsive explosions of rockets. For more than one million years, all human fires were made by burning vegetation, and wood in particular. What was fire doing? Energy stored by plants, trees in particular, was violently released by controlled fires for human-serving purposes of warmth, light, food preparation (to obtain more energy from food) and protection from predation, and it also became the heart of social gatherings. Humans have stared into fires for a million years or more.

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