Help Scientific Method 4. After several generations of predation, make a predict
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Help Scientific Method 4. After several generations of predation, make a prediction about which allele, if any, would decline in the black background environment and describe why? (1 point) 5. After several generations of predation, make a prediction about which allele, if any, would you expect to decline in the white background environment and describe why? (1 point) 6. After several generations of predation, make a prediction about which allele, if any, would you expect to decline in the gray background environment and describe why? (1 point) 7. In either a black or white background, if you continued the same predation simulation for 100 generations, do you think that the frequency of the B or b allele (that is, p and q) would go to zero or 1.0? (Would one of the alleles be eliminated from the gene pool?) Why or why not? Cite evidence from your experiment and the experiments of your classmates. (4 points)Explanation / Answer
Natural selection is the differential survival and reproduction of individuals with certain traits. It acts on phenotypes. Because most phenotypes are, in part, determined by genotypes, natural selection causes a change in the frequency of alleles over time. Thus, natural selection operates whenever individuals in a population differ in their ability to survive and reproduce, and natural selection causes evolution whenever there is genetic variation for traits that affect fitness both the factors work hand in hand.
Fitness is the ability of an organism to survive, and make copies of its alleles that are represented in the next generation. Organisms that produce more surviving offspring are more fit, those that produce fewer are less fit. Differences in fitness may be due to differences in survivorship, differences in fecundity, or both.
Any allele that affects either or both of these will be subject to natural selection. However, there are alleles that decrease survivorship, but increase fecundity, and vice versa.
Predation is a ubiquitous and powerful agent of natural selection seen among the organisms that are separated by their strengths and weakness. Predation occurs when one organism devours another, thus keeping the victim from passing on any more copies of its genes. Prey organisms are under constant natural selection to evolve defenses from predation.
The relationships between predator and prey, and parasites and hosts, have coevolved over long periods of time. About 50 years ago,the interaction between parasite and host (or predator and prey) seems to resemble an evolutionary arms race: a. First a parasite (or predator) evolves a trait that allows it to attack its host (or prey). b,Next, natural selection favors host individuals that are able to defend themselves against the new trait. c. As the frequency of resistant host individuals increases, there is natural selection for parasites with novel traits to subvert the host defenses.This process continues as long as both species survive.Some possible defenses against predators include defensive behavior, toxins, sheer size, armor, speed, crypsis, and mimicry.
Small populations are generally at a greater risk of extinction than large populations. They are subject to rapid declines in numbers for three main reasons: loss of genetic variability and related problems of inbreeding and genetic drift
based on this background-
4. Selection is weak against homozygous recessive rare alleles. Reason - As recessive alleles get rarer and rarer, selection against deleterious recessives becomes weaker and weaker, because most copies exist in the heterozygous state and are not expressed. Likewise, selection is weak in favor of rare advantageous alleles for the same reason, and rare favorable mutations that are recessive may be lost by genetic drift before they become common.
5. Particular pheonotype, representing a particular combination of alleles at various loci, has a fitness that is a function of its environment. Some homozygous dominant alleles confer a high fitness under one set of circumstances, and a low fitness under others. For example, alleles that favor DDT resistance in mosquitoes confer very high fitness under conditions where the pesticide is being sprayed, but are deleterious in its absence. Thus, changes in the environment may reverse the effects of selection. Based on the fossil record, changes in the direction of selection seem to be the rule rather than the exception.
It is important to remember that natural selection has no plan, no memory, and no goal. It is a stochastic process, and has no intellect or creative power. Its cumulative effects over time, however, can be incredible. In this sense, it is like continental drift, a nonthinking process that produces incredible, beautiful, and complicated results.
6. all the organisms that are heterozygous meaning they have two alleles in their gane will disappear in the long run. Frequency-dependent selection occurs when the fitness of a phenotype is a function of how common that phenotype is. Positive frequency-dependent selection occurs when the most common phenotype, whatever it happens to be, is most fit. When applied to alleles at a locus, it means that the most common allele has the highest fitness. Negative frequency-dependent selection occurs when the least common phenotype, whatever it happens to be, is most fit. When applied to alleles at a single locus, it means that the least common allele has the highest fitness. Note that balancing selection is also negative frequency-dependent selection. It is one of the few forms of natural selection that can act to preserve genetic variation, most forms of natural selection lead to the loss of genetic variation as unfit alleles are "weeded out" of the population.
7. certain adaptations can help overcome predation and help in survival thus ensures the continuatin of the species they are- Crypsis is the evolutionary modification of an organisms morphology, color, smell, or behavior, to avoid being detected. Predators can also be cryptic to avoid being detected by potential prey. Mimicry is a widespread evolutionary adaptation to resemble species that predators are likely to recognize as poisonous. Batesean Mimicry-is deceptive, mimic is harmless. Mullerian Mimicry-mimic is harmful. The advantage is that predators are more likely to recognize potential trouble and not eat the mimic.
Plants have a range of defenses against herbivores as well. Passive defenses are always present. These include toxins, spines, silica, tannins. Silica erodes mammal teeth. Tannins impede edibility, digestibility, nutrition.
Induced defenses are present when the plant is under attack. These include a variety of toxins. Otherwise the plants can simply evolve to tolerate herbivory.
demographic fluctuations due to random variations in birth and death rateRelated Questions
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