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Chapter 18: Problem 7

What are homologous structures? a. physical structures that have no apparent function b. parallel structures in diverse organisms c. physical structures that are used only occasionally d. similar structures in diverse organisms

Short Answer

Expert verified
d. similar structures in diverse organisms

Step by step solution

01

Understand the Definition

Homologous structures are physical features in different organisms that have a similar structure but may not necessarily have the same function. These structures arise from a common ancestor.
02

Analyze Each Option

Review each provided option to determine whether it matches the definition of homologous structures:a. Physical structures that have no apparent functionb. Parallel structures in diverse organismsc. Physical structures that are used only occasionallyd. Similar structures in diverse organisms
03

Match the Definition

Option d. 'similar structures in diverse organisms' fits the definition of homologous structures, as it emphasizes similarity due to common ancestry.
04

Verify and Conclude

Confirm that option d is the most accurate. Homologous structures are indeed similar structures in diverse organisms, derived from a common ancestor.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Evolutionary Biology
Evolutionary biology is the study of how life evolves over time. This scientific field explores how different species change and adapt. It also looks at the origins of life and how complex organisms evolve from simple ancestors.
One of the key ideas in evolutionary biology is natural selection. It is the process that drives evolution. Natural selection occurs when organisms with traits that are better suited to their environment tend to survive and reproduce more. Over many generations, these traits become more common in the population.
Homologous structures are an important piece of evidence for evolution. They help scientists understand how different species are related. By comparing these structures, scientists can trace back the evolutionary history of organisms and learn how they diverged from common ancestors.
Common Ancestry
Common ancestry refers to the idea that different species share a common ancestor. This means that many species we see today have evolved from the same ancient organism. Think of it like a family tree. Just as you share common ancestors with your cousins, different species share common ancestors too.
Homologous structures are a clear indicator of common ancestry. These structures have a similar form and origin but may have different functions in different organisms. For example:
  • The forelimb of a human
  • The wing of a bird
  • The flipper of a whale
      • All of these limbs are built on the same basic bone structure. This suggests that humans, birds, and whales share a common ancestor from which these structures have evolved.
      Observing these similarities helps scientists map out the evolutionary relationships between different species. It highlights how diverse organisms can evolve different features suited to their distinct environments, all stemming from a shared origin.
Comparative Anatomy
Comparative anatomy is the study of similarities and differences in the anatomy of different species. This field is crucial for understanding evolutionary biology and common ancestry. By comparing the anatomical structures of various organisms, scientists can infer how these species are related and how evolutionary changes have taken place.
Homologous structures are a primary focus in comparative anatomy. These are structures in different species that are similar in form but may serve different purposes. For example:
  • The arm of a human is adapted for lifting and manipulating objects.
  • The wing of a bat is adapted for flying.
  • The leg of a horse is adapted for running.
Despite their different functions, these limbs have a similar bone structure. This points to a shared evolutionary past. Comparative anatomy goes beyond just bones. It also looks at organs, muscles, and other physical features. By examining these similarities and differences, scientists can piece together the puzzle of life's history.
Understanding comparative anatomy not only helps in studying evolution but also provides insights into how different species adapt to their environments and survive over time.

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Most popular questions from this chapter

Which statement about postzygotic barriers is false? a. They occur after fertilization. b. They include hybrids that are sterile. c. They include hybrid organisms that don鈥檛 survive the embryonic stage. d. They include reproductive organ incompatibility

Give an example of convergent evolution and explain how it supports the theory of evolution by natural selection. a. An example of convergent evolution is the development of the same function, swimming, in organisms that live in different parts of the globe, such as Arctic beluga whales and Antarctic right whales. The fact that organisms that do not come in contact with each other have developed the same traits suggests that natural selection can produce similar adaptations in organisms who share a similar environment b. An example of convergent evolution is the set of adaptations, such as better running speed or more efficient hunting, developed by a species in response to competition with a new species that moves into the same region. The fact that a species adapts after it comes into contact with a competitor suggests that natural selection works more quickly with higher selective pressures. c. An example of convergent evolution is the development of an ancestral structure, a limb, into two different modern structures, such as a hand and a flipper. The fact that natural selection can cause a structure to develop down two different pathways due to different environmental conditions supports the theory of evolution d. An example of convergent evolution is the development of the same function, flying, in organisms that do not share a recent common ancestry, such as insects and birds. The fact that wings that allow flight have developed from very different original structures suggests that the process of natural selection can produce similar adaptations in two very different types of organisms who share a similar environment

Which are two primary sources of genetic variation? a. mutations and sexual reproduction b. isolation and sexual reproduction c. sexual reproduction and asexual reproduction d. migration and sexual reproduction

The upper forelimbs of humans and cats have fairly similar structures. In contrast, the upper forelimbs of whales (their flippers) have bones with a different shape and proportion from both cats and humans. Interestingly, genetic data suggests that all three organisms have a common ancestor from about the same point in time. What is a likely explanation for these data? a. Cats and humans are more closely related to each other than either are to whales. b. The shape of the whale forelimb arose a result of disadvantageous mutations c. The whale flipper is an adaptive characteristic unique to its water environment. d. The whale flipper is a vestigial structure

In 1795, a Scottish geologist named Charles Hutton suggested that Earth鈥檚 geologic features could be explained by gradual processes that were still operating. This was in direct contrast to other scientific thought at the time, which included well-accepted proposals that geologic layers were representative of catastrophic events caused by processes no longer operating in the present time. Hutton proposed geologic features as the result of slow and consistent change, such as valleys formed by rivers wearing through rock. Hutton鈥檚 ideas were incorporated in the work of Charles Lyell, a geologist working in Darwin鈥檚 time. Lyell advocated a principle called uniformitarianism, the consistency of mechanisms of change over time. In other words, Lyell argued that the same geologic processes operating in the present had operated in the past, and at the same rate. The ideas of Hutton and Lyell influenced the work of Charles Darwin. How do Hutton鈥檚 and Lyell鈥檚 ideas connect to and provide support for Darwin鈥檚 theory of evolutionary change? a. The idea that the same processes that operate in the present also operated in the past, and at the same rate, supported Darwin鈥檚 hypothesis of natural selection because humans could select for desirable traits and produce change very rapidly, so natural selection would also be fast enough to produce the full range of diversity in living organisms. b. The idea that the same processes that operate in the present also operated in the past, and at the same rate, connects to Darwin鈥檚 hypothesis of natural selection because he had observed it happening in the present c. The idea that geologic change is the result of slow, continuous processes rather than sudden, substantial change connects to Darwin鈥檚 support of gradualism rather than punctuated equilibrium as the process that guided evolution. d. The idea that geologic change is the result of slow, continuous processes rather than sudden, substantial change connects directly to Darwin鈥檚 hypothesis that, given enough time, slow and subtle processes could produce substantial biological change.
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