Guided Reading 16.2 (Modern Evolutionary Classif.) Name: ______

Date: ______Period ______

1.  ______Are Most Important?

2.  The use of ______is not simple, however, because there is not just one molecular clock ______. Instead, there are many, each of which "ticks" at a different rate.

3.  Think of a ______. If you want to time a brief event, you pay attention to the ______.

4.  To time an event that ______, you use the ______or the hour hand.

5.  Linnaeus grouped species into ______, such as genus and family, mainly according to ______similarities and differences.

6.  Or would you call them ______because they ______and feed their young ______?

7.  Biologists now group organisms into ______that represent lines of ______, or phylogeny, not just physical ______.

8.  Darwin's ideas about ______have given rise to the study of ______, or evolutionary relationships among organisms.

9.  The ______organisms together based on their evolutionary history is called ______.

10. Species within a ______are more closely related to each another than to species in ______.

11. Similarly, all ______in a ______share a ______.

12. The higher the level of the taxon, the ______is the common ancestor of all the ______in the taxon.

13. ______, operating on species in similar ecological ______, has often caused ______evolution..

14. ______showed that the DNA sequences of the ______and the ______were more similar than those of the ______and the ______.

15. A ______also relies on a repeating process to mark time—______.

16. ______that appear in ______parts of a lineage but not in its older members are called ______.

17. ______can be used to construct a ______, a diagram that shows the ______among a group of organisms.

18. One such shared ______is a segmented body. Another is a ______..

19. ______the DNA level in the ______of organisms can be used to help determine ______.

20. But even ______with very different anatomies have ______.

21. Because ______are so similar across all forms of life, these molecules provide an excellent way of ______at their most basic level—their ______.

22. Even the ______such as humans and yeasts show many ______.

23. ______one example of similarities at the ______level—an indicator that humans and yeasts share a ______.

24. The more ______sequences of two species, the more recently they shared a ______, and the more closely they are related in ______

25. Adult barnacles have ______and a body divided into ______. Barnacles periodically ______, their external skeleton.

26. These ______make barnacles more similar to ______than to ______.

27. ______occur all the time, causing slight changes in the ______, as shown in Figure 18-9.

28. Some mutations have a ______on an organism's phenotype. These mutations are under ______pressure from ______.

29. Other mutations have ______on phenotype. These ______mutations accumulate in the DNA of ______at about the ______.

30. Predict how the field of ______has changed since ______time

31. Early ______grouped organisms together based on ______.

32. ______above the level of species are "invented" by researchers who decide how to distinguish between one ______, and another.


18-2 Section Assessment

1. Key Concept -- How is information about evolutionary, or phylogenetic, relationships useful in classification?

2. Key Concept -- How are genes used to help scientists classify organisms?

3. What is the principle behind cladistic analysis?

4. What gene indicates that yeasts and humans share a common ancestor?

5. Describe the relationship between evolutionary time and the similarity of genes in two species.

6. Critical Thinking (Inferring) -- Would a barnacle's DNA be more similar to the DNA of a crab or that of a limpet? Explain.

Thinking Visually

Constructing a Chart -- Draw a cladogram of a manufactured item, such as an automobile or a household appliance, that has changed over the years. Label derived characters that appeared as new models arose. For example, automobiles came to have electronic fuel injection and antilock brakes.

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