- Laws of Inheritance – Concepts of Biology – 1st Canadian Edition
- Law of Dominance
- How Hardwired Is Human Behavior?
- How Hardwired Is Human Behavior?
When Donna saw the figure, her first impression was of some strange artwork. What the fuck? Is he one of ours? Never mind what you drag back in. She folded her arms in defense of it.
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- How Hardwired Is Human Behavior??
- Darwin, evolution, & natural selection (article) | Khan Academy.
Rachel looked at John for support, but got only pursed lips and a downcast head in return. Donna thought about it. She stepped back and studied the form from head to toe. She had worked on patients with a wide range of unsavory, often disgusting, conditions, especially since landing on Verde, but this one was the worst by far. The skin was loose, shrunken and grayish. The limbs, stiff and tortured, were strange, and she got the distinct impression that one arm was longer than its mate. The thought of working on it turned her stomach. She drew a breath and thought about it some more, trying to find some reason to do it.
When she took her hand away, she wiped and whisked her fingers together to clean them and felt compelled to wash her hands several times. A few minutes later, she was ready to work, gloves on and an assortment of glass and stainless steel implements in a tray, clean and waiting. The flesh felt tough and dry but was loose and seemed to float over a layer of congealed material beneath. She filled a needle with painkiller and injected the contents into a vein she found in his arm.
A moment later, she thought she heard just the slightest sigh from him, like a distant and gentle breath, so weak it was barely audible.
She inserted an IV into the same vein, taped it down, and started a flow of nutrients from a bottle. That done, she tightened her gloves over her interlocked fingers, and began. The entire length of it was covered with brownish fluid that seemed to lubricate it. It continued to writhe, making light slithering noise against the hollow pan. She pulled the other tendrils out, one by one from his ears, nostrils and a few that had chosen to pierce the sides of his head directly.
Those were smaller, but she wondered how she was going to close those stab-like wounds whose edges were already healed over. When the last probe was removed, she pried the globular body off his head with her fingers and added it to the pile of wet and tangled tendrils in the pan. Toggle navigation.
ADS 8. To learn more about population size as it relates to genetic drift , visit this advanced article. We have invented medical treatments, agricultural practices, and economic structures that significantly alter the challenges to reproduction and survival faced by modern humans. So, for example, because we can now treat diabetes with insulin, the gene versions that contribute to juvenile diabetes are no longer strongly selected against in developed countries. However, this is not the case.
Humans still face challenges to survival and reproduction, just not the same ones that we did 20, years ago. The direction, but not the fact of our evolution has changed. Scientists have uncovered many such cases of recent human evolution. For example, many bacteria reproduce mainly asexually. How can the biological species concept be applied to them?
Many plants and some animals form hybrids in nature, even if they largely mate within their own groups. Should groups that occasionally hybridize in selected areas be considered the same species or separate species? The concept of a species is a fuzzy one because humans invented the concept to help get a grasp on the diversity of the natural world.
To learn more about the biological species concept , visit Evolution To learn about other species concepts , visit this side trip.multiphp-nginx.prometdev.com/fyhid-tienda-azitromicina-250mg.php
Laws of Inheritance – Concepts of Biology – 1st Canadian Edition
Natural selection naturally results from genetic variation in a population and the fact that some of those variants may be able to leave more offspring in the next generation than other variants. Either an individual has genes that are good enough to survive and reproduce, or it does not; it can't get the right genes by "trying. Instead, resistance evolves because random mutation happens to generate some individuals that are better able to survive the antibiotic, and these individuals can reproduce more than other, leaving behind more resistant bacteria.
If a population happens to have genetic variation that allows some individuals to survive a challenge better than others or reproduce more than others, then those individuals will have more offspring in the next generation, and the population will evolve. If that genetic variation is not in the population, the population may survive anyway but not evolve via natural selection or it may die out.
But it will not be granted what it "needs" by natural selection. Of course, some species may possess traits that allow them to thrive under conditions of environmental change caused by humans and so may be selected for, but others may not and so may go extinct. If a population or species doesn't happen to have the right kinds of genetic variation, it will not evolve in response to the environmental changes wrought by humans, whether those changes are caused by pollutants, climate change, habitat encroachment, or other factors. For example, as climate change causes the Arctic sea ice to thin and break up earlier and earlier, polar bears are finding it more difficult to obtain food.
If polar bear populations don't have the genetic variation that would allow some individuals to take advantage of hunting opportunities that are not dependent on sea ice, they could go extinct in the wild. However, this impression is incorrect.
Natural selection has no foresight or intentions. In general, natural selection simply selects among individuals in a population, favoring traits that enable individuals to survive and reproduce, yielding more copies of those individuals' genes in the next generation. Theoretically, in fact, a trait that is advantageous to the individual e. So what's the evolutionary explanation for altruism if it's not for the good of the species?
Law of Dominance
There are many ways that such behaviors can evolve. For example, if altruistic acts are "repaid" at other times, this sort of behavior may be favored by natural selection. Similarly, if altruistic behavior increases the survival and reproduction of an individual's kin who are also likely to carry altruistic genes , this behavior can spread through a population via natural selection. Advanced students of evolutionary biology may be interested to know that selection can act at different levels and that, in some circumstances, species-level or group-level selection may occur.
However, it's important to remember that, even in this case, selection has no foresight and is not "aiming" at any outcome; it is simply favoring the reproducing units that are best at leaving copies of themselves in the next generation. To learn more about levels of selection , visit our side trip on this topic. An organism's evolutionary fitness does not indicate its health, but rather its ability to get its genes into the next generation.
The more fertile offspring an organism leaves in the next generation, the fitter it is. This doesn't always correlate with strength, speed, or size. To learn more about evolutionary fitness , visit Evolution In most populations, organisms with many different genetic variations survive, reproduce, and leave offspring carrying their genes in the next generation. It is not simply the one or two "best" individuals in the population that pass their genes on to the next generation.
This is apparent in the populations around us: for example, a plant may not have the genes to flourish in a drought, or a predator may not be quite fast enough to catch her prey every time she is hungry. These individuals may not be the "fittest" in the population, but they are "fit enough" to reproduce and pass their genes on to the next generation. There are many reasons that natural selection cannot produce "perfectly-engineered" traits.
How Hardwired Is Human Behavior?
And of course, because organisms have arisen through complex evolutionary histories not a design process , their future evolution is often constrained by traits they have already evolved. For example, even if it were advantageous for an insect to grow in some way other than molting, this switch simply could not happen because molting is embedded in the genetic makeup of insects at many levels.
To learn more about the limitations of natural selection , visit our module on misconceptions about natural selection and adaptation. Some may be the chance results of history. There is nothing special about the relationship between GGC and glycine. It's just a historical accident that stuck around.
Others traits may be by-products of another characteristic. For example, the color of blood is not adaptive. There's no reason that having red blood is any better than having green blood or blue blood. Blood's redness is a by-product of its chemistry, which causes it to reflect red light. The chemistry of blood may be an adaptation, but blood's color is not an adaptation. To read more about explanations for traits that are not adaptive , visit our module on misconceptions about natural selection and adaptation.
To learn more about what traits are adaptations , visit another page in the same module. Back to top Misconceptions about evolutionary trees.
How Hardwired Is Human Behavior?
Organisms that share a more recent branching point i. For example, on the tree below, taxon A is adjacent to B and more distant from C and D. However, taxon A is equally closely related to taxa B, C, and D. Similarly, in the tree below, taxon B is adjacent to taxon A, but taxon B is actually more closely related to taxon D. That's because taxa B and D share a more recent common ancestor labeled on the tree below than do taxa B and A.
It may help to remember that the same set of relationships can be portrayed in many different ways. The following phylogenies are all equivalent. Even though each phylogeny below has a different order of taxa at the tips of the tree, each portrays the same pattern of branching.