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Ch. 22 - Evolution by Natural Selection

Chapter 21, Problem 10

The geneticist James Crow wrote that successful scientific theories have the following characteristics: (1) They explain otherwise puzzling observations; (2) they provide connections between otherwise disparate observations; (3) they make predictions that can be tested; and (4) they are heuristic, meaning that they open up new avenues of theory and experimentation. Crow added two other elements of scientific theories that he considered important on a personal, emotional level: (5) They should be elegant, in the sense of being simple and powerful; and (6) they should have an element of surprise. How well does the theory of evolution by natural selection fulfill these six criteria?

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Welcome back. Here's our next question. All of the following are pieces of evidence of evolution by natural selection Except so we're going to be looking for the one choice that would not be evidence for evolution by natural selection. So let's just recall very briefly from our content videos, what you know, what is the definition of evolution by natural selection? Well, it would be the change in inheritable traits characteristic of a population over generations. Do two. The differential survival and reproduction of individuals due to differences in phenotype. So that's a long wordy way of reminding us that we have individual organisms that develop variations, mutations uh that cause differences in the phenotype of individuals of the same species and the environmental pressures around them cause certain of those phenotype is to have an advantage allowing those individuals to be more likely to survive and reproduce. And as certain phenotype sis lend an advantage those phenotype become favored in the genotype sis of the descendants. So the inheritable traits characteristic of an entire population change over generations and that can can cause um speciation. So you can start with an original ancestral species uh which begins to diverge if it takes advantage of two different environments or two different or it ends up in two different locations. So let's look at our answer choices to look for the one that is not evidence for this method of evolution. So choice a says many species share similar physical features. While this would be evidence because you could say that species that face similar environmental pressures. So similar food sources similar. Um You know whether they live in murky water or something and they have had the same phenotype sis favored the same phenotype give them a reproductive advantage uh due to that natural selection. So that is evidence for evolution by natural selection. So that's not our answer. Choice choice B says the unique features of island species. Well this is definitely evidence of evolution by natural selection. This was of course what led Darwin to the theory of evolution, seeing the finch species being existing in such different phenotype on different islands because it had adapted to take advantage of different food sources. So that's not our answer. Either choice C says conserved sequences in the DNA. Well this is uh evidence also because we see um we can trace back to ancestral species by looking at sequences that are conserved in species descended from a common ancestor. So we can see that they diverged from a common ancestor and became different from each other. We can see conserved sequences among related species. Um So that's not our answer. So finally we're on Choice D. No two individuals can have conserved DNA sequences as each individual is unique. Well this would not be evidence because it's not true. Um you know, all individuals that are members of a shared group have conserved sequences of DNA that show us that related nous between species or descent from a common ancestor. So which is not evidence of evolution by natural selection. That's choice D No. Two individuals can have conserved DNA sequences as each individual is unique. See you in the next video.
Related Practice
Textbook Question

Why don't the biggest and strongest individuals in a population always produce the most offspring? a. The biggest and strongest individuals always have higher fitness. b. In some environments, being big and strong lowers fitness. c. Sometimes the biggest and strongest individuals may choose to have fewer offspring. d. Sometimes the number of offspring is not related to fitness.

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Textbook Question

Evaluate this statement: Evolution is said to occur when new traits accumulate over time, increasing complexity.

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Textbook Question

The global “One Health” movement fosters collaborations at the intersection of human health, veterinary health, and environmental health. Explain why “One Health” seeks to reduce the use of antibiotics in farm animals to improve human health.

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Open Question

Over half of the world’s human population lives in cities. Are species adapting to life in these novel urban environments? A global team of researchers (including Tiffany Longo, Jesse Bragger, and Summer Shaheed, shown in in the photo) used white clover as a study system to find out. They measured the production of a compound called hydrogen cyanide (HCN) in rural and urban clover plants. Production of HCN deters herbivores and increases tolerance to drought but has a cost: Clover must expend energy to produce HCN.

Compare how evolution by inheritance of acquired characters and the theory of evolution by natural selection would explain the observation that HCN production is often high in rural environments with many herbivores and low in urban environments with few herbivores.

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Textbook Question

Most mice living on the mainland of Florida are brown, but the mice that live on the sand dunes of the barrier islands have white fur. The differences in color are heritable, determined by genes such as MC1R. It is intuitive that the light color of beach-dwelling mice is an adaptation for blending into their environment—and thus evading predators. What is an evolutionary adaptation? a. a trait that improves the fitness of its bearer, compared with individuals without the trait b. a trait that changes in response to environmental influences within the individual's lifetime c. the ability of an individual to adjust to its environment d. a trait that an individual wants so that it can survive

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Open Question

Over half of the world’s human population lives in cities. Are species adapting to life in these novel urban environments? A global team of researchers (including Tiffany Longo, Jesse Bragger, and Summer Shaheed, shown in in the photo) used white clover as a study system to find out. They measured the production of a compound called hydrogen cyanide (HCN) in rural and urban clover plants. Production of HCN deters herbivores and increases tolerance to drought but has a cost: Clover must expend energy to produce HCN.

The production of HCN is a heritable Mendelian trait controlled by just two unlinked genes (Ch. 14, Section 14.2; clover plants with at least one dominant allele produce HCN, but plants that are homozygous recessive for both genes produce no HCN). Apply Darwin’s four postulates to explain natural selection for low HCN production in a population of clover living in a city with few herbivores and ample water.

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