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What must exist in a population before natural selection can act?
Competition + Variation. Classic example: Giraffes not always had long necks. There were variation in the species. When food sauces grew low competition increases and those with longer necks survived (more fruit/food at the top of trees) as they were more suited to the conditions. These long necked giraffes then breed and the offspring have long necks, thus natural selection of a "fitter" species. Hense - survival of the fittest.
Natural selection is based on what 5 observations?
The theory of natural selection is based on the following assumptions about the nature of living things: 1. All organisms produce more offspring than can survive. 2. No two organisms are exactly alike. 3. Among organisms, there is a constant struggle for survival. 4. Individuals that possess favorable characteristics for their environment have a higher rate of survival and produce more offspring. 5. Favorable characteristics become more common in the species, and unfavorable characteristics are lost.
What happens in the process of natural selection?
Evolution means natural change over time. Natural selection means that we humans do not make the environment change. Just let nature take its' course. For millions of years, changes were made naturally that benefited the organism. The genes that it had were passed on. Other organisms were not as fit and their genes died with them.But we have made changes by inferring; this includes having milk cows that produce more and more milk over the generations. Wild cattle do not have the large udders that dairy cows do. Even pulling weeds makes "unnatural" changes. There are many more examples.
What are the four rules of natural selection?
Natural selection has no 'steps'. It is a continous process of filtering. However, there are a couple of key factors in natural selection, prerequisites that have to be met for natural selection to occur:Overproduction-many organisms are producedGenetic Variation-some organisms have different genetic traits than othersStruggle to Survive or Survival of the Fittest-The organisms with the traits better suited for their environment live while others die offSuccessful Reproduction-The living organisms produce giving their offspring better traits to survive.This process goes on changing a whole species. It is a big part of evolution. This helps organisms become the best suited to their environment that they can.
What was Charles Darwin's Theory of Evolution?
Charles Darwin's theory of natural selection applies to organisms who adapt to their environment better than others and survive to pass on their traits to offspring. Due to variation in their genes, may be caused by mutation but rarely so, organisms are able to adapt to their environment. If they don't adapt well they die. If they adapt to their environment it means that they have fought for their survival and are now able to pass on their variations to their offspring and make them stronger. Often as a result a new species is formed due to the accumulated differences.There are three types of natural selection: Directional, disruptive, and stabilizing selection. In directional selection only one extreme genotype is favored to pass on. Meaning the environment chooses one genotype to pass on. An extreme genotype for example would be either SS or ss for sickle cell, either the genotype for sickle cell is passed on or the non-sickle cell genotype is passed on. In disruptive selection, a disruption separates similar organisms causing the favoring of two extreme genotypes. For example both SS and ss are favored to pass on. In stabilizing selection only the middle genotype is favored meaning Ss which is carrier of sickle cell.Natural selection is when the environment determines which alleles enable organisms to survive.The theory of natural selection states that traits in a species become more or less prevalent depending on environmental pressures that select either for or against such traits.Individuals that have traits that better suit their environment are more likely to survive.Darwin broke down the process into 4 steps:1. individuals that make up a population vary in their traits2. some of these trait differences are heritable3. in each generation, many more offspring are produced than can survive. Only some individuals survive. Of these, some will produce more offspring than others4. Individuals with certain heritable traits are more likely to survive and reproduce.Natural Selection occurs when individuals with certain traits produce more offspring than do individuals with certain traits produce more offspring that do individuals without those traits.when organism adapt to the environment they will be likely to survive and produce healthy offspring.
What is a type of selection in which individuals at both ends of the distribution curve have higher fitness than those near the middle?
disruptive selection
What is the type of selection where individuals nears the center of a distribution curve have higher fitness than those at the extremes?
It's usually called stabilizing selection.
When individuals near the center of the curve have higher fitness than individuals at either end of the curve?
Stabilizing Selection
When the largest organisms are most fit it shows what kind of selection?
When the largest organisms are most fit, it shows a pattern of directional selection, where individuals at one extreme of a trait distribution have higher fitness. This can lead to a shift in the trait distribution over time, favoring the larger size.
What type of natural selection takes place when individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle?
Disruptive selection.
What are the differences between directional selection and disruptive selection in the process of natural selection?
Directional selection occurs when individuals at one extreme of a trait have a higher fitness, leading to a shift in the population towards that extreme. Disruptive selection occurs when individuals at both extremes of a trait have higher fitness, leading to the population splitting into two distinct groups.
The type of selection in which individuals at one end of a curve have the highest fitness is called?
Directional selection. In this type of selection, the advantageous trait in a population shifts towards one extreme as individuals with that trait have higher fitness and are more likely to survive and reproduce.
What type of selection always results in the narrowing of the bell curve distribution of alleles?
Directional selection always results in the narrowing of the bell curve distribution of alleles. This occurs when individuals at one extreme of the phenotypic range have a higher fitness, causing the frequency of the alleles associated with that extreme to increase in the population over time.
What type of selection may eliminate intermediate phenotypes?
Disruptive selection can eliminate intermediate phenotypes by favoring extreme phenotypes, leading to a bimodal distribution. This selection occurs when individuals with extreme traits have a higher fitness than those with intermediate traits, resulting in the reduction of the intermediate phenotype in the population.
Three ways natural selection picks a phenotype?
stabilizing selection: when individuals near the center of the curve have a higher fitness than individuals at either end of the cure, keeping the center at its current location but narrows the overall graph directional selection: when individuals at one end of the curve have a higher fitness than individuals at the other end, or middle, causing the entire curve to move as the character trait changes disruptive selection: when individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle, causing the single curve to be cut into two These three types of selection are brought about by natural selection, so whichever one is favored, then the genes evolve in that specific direction. natural selection acts on the genotype, but the results are seen in the phenotype
When individuals at only one end of the bell curve of phenotype frequencies have high fitness the result is?
Directional selection, where individuals with phenotypes at one extreme of the bell curve have a higher fitness compared to others. This can result in a shift in the population towards that extreme phenotype over generations.
Does stabilizing selection favors average individuals?
Yes, stabilizing selection favors average individuals by selecting against extreme phenotypes and maintaining the status quo. It arises when individuals with intermediate traits have a higher fitness compared to those with extreme traits, leading to a reduction in genetic variation over time.
