Chapter 25 Reading Quiz

2. Chapter 25 Reading Quiz • What is the evolutionary history of a species called? • Which isotope has a half-life of only 5,730 years? • What was the supercontinent called 250 million years ago? • The mass extinction 65 million years ago marked the end of what era? • All related Orders belong to what taxonomic grouping?

3. 1. Explain the importance of the fossil record to the study of evolution. • Biologists reconstruct evolutionary history by studying the succession of organisms in the fossil record • Phylogeny  the evolutionary history of a species • Fossil record  the ordered array in which fossils appear within layers of rock that mark the passing of geological time 

4. 2. Describe how fossils form. • Usually from mineral-rich hard parts of organisms (bones, teeth, shells of invertebrates) since most organic substances usually decay rapidly  some fossils in layers of sandstone or shale retain organic material  other fossils are molds in mud, etc.  trace fossils like footprints, animal burrows, etc. can also exist 

5. 3. Distinguish between relative dating and absolute dating. • Relative dating  this record chronicles the relative ages of fossils, showing order of evolution  “strata” are rock layers from different time periods; younger strata are on top of older  the succession of the fossil species chronicles phylogeny since fossils in each layer represent that time period 

6. #3 continued…. • Absolute dating  gives the age of the fossils in years  done by radiometric dating, which is the very next question 

7. 4. Explain how isotopes can be used in absolute dating. • Fossils contain isotopes of elements that have accumulated in the living organisms • Radioactive isotopes have fixed half-lives and comparing the ratio of isotopes in a fossil a year can be determined  this is not affected by temperature, pressure, etc. • Ex: C14 has a half-life of 5600 years, meaning that ½ of C14 in a specimen will be gone in 5600 years, etc.  only useful in dating fossils less than 50, 000 years old. 

9. 5. Explain how continental drift may have played a role in the history of life. • Phylogeny has a biogeographical basis in continental drift  spatial distribution of life • North America and Europe moving apart 2cm/year  250 mya Pangaea came together  180 mya Pangaea began breaking up - puzzle is explained by the pattern of continental separations  matching fossils from coastlines (South America and Africa) 

11. 6. Describe how radiation into new adaptive zones could result in macroevolutionary change. • Intervals of extensive turnover included explosive adaptive radiation of major taxa • Ex: evolution of wings allow insects to enter a new adaptive zone • Ex: evolution of shells and skeletons in a few key taxa led to a large increase in the diversity of sea animals between the Precambrian and Paleozoic eras 

12. 7. Explain how mass extinction could occur and affect evolution of surviving forms. • Extinctions may be caused by habitat destruction or by unfavorable environmental changes  not only are many species eliminated, but those that survive are able to undergo new adaptive radiations into the vacated adaptive zones and produce new diversity 

15. 8. List the taxonomic categories from the most to the least inclusive. • Kingdom (Ex: Animals) • Phylum / Division • Class • Order • Family • Genus • Species (Ex: Homo sapiens) 

17. 9. Distinguish between homologous and analogous structures. • Homology  likeness attributed to shared ancestry ex: wings of birds and bats both are modifications of the vertebrate forelimb and thus are homologous • Analogy  similarities due to convergent evolution, not common ancestry ex: insect wings and bird wings evolved independently and are constructed from entirely different structures 

18. Ocotillo & Allauidia

19. 10. Explain why it is important when constructing a phylogeny to distinguish between homologous and analogous character traits. • Generally the greater the amount of homology, the more closely related the species • Adaptation and convergence often obscure homologies, although studies of embryonic development can expose homology that is not apparent in mature structures 

20. 11. Describe four techniques used in molecular systematics and explain what information each provides. • Protein comparison  similarities in amino acid sequences of two proteins from different species indicates that the genes for those proteins evolved from a common gene present in a shared ancestor • DNA and RNA comparisons  a. DNA-DNA hybridization – compares whole genomes by measuring the degree of H bonds between 2 sources b. restriction maps – information about the match-up of specific DNA nucleotide sequences (restriction enzymes) c. DNA sequence analysis – most precise by comparing DNA as it determines the actual nucleotide sequence of a DNA segment 

21. #11 continued…. 3. Identifying and comparing homologous DNA sequences  comparing corresponding DNA segments from two species 4. Molecular clocks  different proteins and nucleic acids evolve at different rates  the number of amino acid substitutions is proportional to the elapsed time since divergence 

22. 12. Distinguish between a monophyletic and a polyphyletic group. • Monophyletic group  single ancestor gave rise to all species in that taxon and to no species in any other taxon • Polyphyletic group  members are derived from two or more ancestral forms not common to all members 

23. 13. Describe the contributions of phenetics and cladistics to phylogenetic systematics. • Phylogenetic systematics = cladistic analysis • Cladistics  produces a cladogram  the sharing of primitive characters indicates nothing about the pattern of evolutionary branching from a common ancestor • Phenetics  comparisons of characters (anatomical characteristics) without sorting homology/analogy  useful for analyzing DNA sequence data and other molecular comparisons between species 

26. 14. Describe how cladistic analysis uses novel homologies to define branch points on phylogenetic trees. • Cladistics classifies organisms according to the order in time that branches arise along a phylogenetic tree 