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Ch. 22 - Evolution by Natural Selection
Chapter 21, Problem 8

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

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Identify the key terms in the statement: 'Evolution', 'new traits', 'accumulate over time', and 'increasing complexity'.
Clarify the definition of evolution: Evolution is the change in the genetic composition of a population over successive generations, often resulting in the development of new traits.
Assess the accuracy of the statement regarding new traits: Evolution does involve the accumulation of new traits in a population, but these traits arise due to mutations, natural selection, genetic drift, and gene flow.
Evaluate the idea of 'increasing complexity': Evolution does not necessarily lead to increased complexity. It can also lead to simpler or more streamlined organisms, depending on the environmental pressures and natural selection.
Conclude the evaluation: The statement is partially correct in that evolution involves the accumulation of new traits over time, but it is misleading to suggest that this always leads to increased complexity.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Evolution

Evolution is the process through which species change over time through mechanisms such as natural selection, genetic drift, and mutation. It explains how organisms adapt to their environments and how new species arise from common ancestors. Understanding evolution is crucial for evaluating claims about the accumulation of traits and complexity in organisms.
Recommended video:
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Introduction to Evolution of Populations

Natural Selection

Natural selection is a key mechanism of evolution, where individuals with advantageous traits are more likely to survive and reproduce. This process leads to the gradual accumulation of beneficial traits in a population over generations. It is important to recognize that natural selection does not necessarily lead to increased complexity; rather, it favors traits that enhance survival and reproduction in a given environment.
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Natural Selection

Complexity in Evolution

The concept of complexity in evolution refers to the idea that organisms can develop more intricate structures and functions over time. However, complexity is not a guaranteed outcome of evolution; it can also lead to simplification or specialization depending on environmental pressures. Evaluating the statement requires understanding that evolution can result in both increased and decreased complexity.
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Origin of Complex Traits
Related Practice
Textbook Question

Explain the logic behind the claim that the nuclear envelope is a synapomorphy that defines eukaryotes as a monophyletic group.

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Textbook Question

Some biologists summarize evolution by natural selection with the phrase 'mutation proposes, selection disposes.' Mutation is a process that creates heritable variation. Explain what the phrase means.

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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

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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Textbook Question

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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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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