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Unit 1:
Ch. 1
Ch. 2
Ch. 3
Interlude A
Unit 2:
Ch. 4
Ch. 5
Ch. 6
Ch. 7
Ch. 8
Ch. 9
Interlude B
Unit 3:
Ch. 10
Ch. 11
Ch. 12
Ch. 13
Ch. 14
Ch. 15
Interlude C
Unit 4:
Ch. 16
Ch. 17
Ch. 18
Ch. 19
Interlude D
Unit 5:
Ch. 20
Ch. 21
Ch. 22
Ch. 23
Ch. 24
Ch. 25
Ch. 26
Ch. 27
Ch. 28
Ch. 29
Ch. 30
Interlude E
Unit 6:
Ch. 31
Ch. 32
Interlude F
Unit 7:
Ch. 33
Ch. 34
Ch. 35
Ch. 36
Ch. 37
Ch. 38
Interlude G

» Getting Started » A Guide to the Reading » Tying it all together

Getting Started

Below are a few questions to consider prior to reading Chapter 16. These questions will help guide your exploration and assist you in identifying some of the key concepts presented in this chapter.

  1. What was the name of the ship on which Charles Darwin sailed to the Galapagos islands?
  2. What household item did the American Medical Association tell U.S. consumers to avoid using in 2000?
  3. What do a person’s arm, a whale’s fin, and a bat’s wing all share in common?
  4. What can the fossil record tell us about how the earth’s environments have changed over time? 
  5. What are vestigial organs?
  6. By what amount does the distance between South America and Africa increase each year?
  7. How can computer programs that mimic natural selection help engineers to develop new inventions?

A Guide to the Reading

When exploring the content in Chapter 16 for the first time, the following concepts typically give students the most difficulty. For each concept, one or more references have been identified which may help you gain a better understanding of these potentially problematic areas.

Mechanisms of Evolution

Evolution within a population occurs when individuals possessing certain characteristics survive and reproduce at a higher rate than other individuals.  As described in the chapter, there are two primary means by which this occurs – natural selection and genetic drift.  While both mechanisms result in the evolution of a population, they accomplish this in very distinct ways.  In natural selection, the characteristics that an individual possesses actually contribute to the individual’s survival and rate of reproduction.  Since these characteristics may be inherited, subsequent generations would also possess these characteristics and also have higher survival and reproduction rates.  Over several generations, this would cause the population to change to reflect the abundance of individuals with these favorable characteristics.  In contrast, genetic drift occurs when natural events remove particular groups of individuals with particular characteristics by chance.  As a result, surviving individuals with distinct characteristics go on to reproduce, passing their inheritable characteristics off to the next generation.  The key to understanding the difference between these mechanisms is realizing that in genetic drift, inheritable characteristics play no role in determining survival.  Survival of individuals with particular characteristics occurs solely by chance.

For more information on this concept, be sure to focus on:

  • Section 16.2, Mechanisms of Evolution
  • Figure 16.2, Natural Selection at Work
  • Figure 16.3, Genetic Drift

Shared Characteristics

As discussed in the chapter, different species may share many characteristics.  Features that are shared between organisms that have a common ancestor are called homologous.  A good example would include the opposable thumbs shared between the great apes and humans.  These two groups of organisms shared a recent common ancestor who likely also had this distinguishing feature.  Analogous features, in contrast, appear when different groups of organisms develop similar characteristics separately through natural selection as a result of similar environmental pressures.  This process is referred to as convergent evolution.  The example provided in the text indicates that the features shared between the distantly related organisms sharks and dolphins (such as large dorsal fins) would have evolved through convergent evolution.  As a result, these features would be considered analogous. 

For more information on this concept, be sure to focus on:

  • In Section 16.3, Organisms share characteristics due to common descent
  • Figure 16.4, Shared Characteristics
  • Figure 16.5, The Power of Natural Selection

Tying it all together

Several concepts presented in this chapter build upon concepts presented in previous chapters and are also revisited and discussed in greater detail in subsequent chapters, including:

Evolutionary Trees and Branching

  • Chapter 2 – Section 2.2, Using Evolutionary Trees to Predict the Biology of Organisms

Genes and Alleles

  • Chapter 10 – Section 10.3, Basic Patterns of Inheritance\

Evolution of Populations

  • Chapter 17 – Section 17.3, Four Mechanisms Can Cause Populations to Evolve


  • Chapter 17 – Section 17.4, Mutation: The Random Production of New Alleles

Genetic Drift

  • Chapter 17 – Section 17.6, Genetic Drift: The Effects of Chance

Natural Selection

  • Chapter 17 – Section 17.7, Natural Selection: The Effects of Advantageous Alleles

Using the Fossil Record to Determine Evolutionary Relationships

  • Chapter 19 – Section 19.1, The Fossil Record: A Guide to the Past

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