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?

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 

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 

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 

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

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. 

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) 

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 

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 

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) 

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 

Ocotillo & Allauidia

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 

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 

#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 

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 

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 

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 