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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece.

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Presentation on theme: "Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece."— Presentation transcript:

1 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 25 Phylogeny and Systematics

2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: Investigating the Tree of Life This chapter describes how biologists trace phylogeny – The evolutionary history of a species or group of related species

3 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Biologists draw on the fossil record – Which provides information about ancient organisms Figure 25.1

4 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Biologists also use systematics – As an analytical approach to understanding the diversity and relationships of organisms, both present-day and extinct

5 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Currently, systematists use – Morphological, biochemical, and molecular comparisons to infer evolutionary relationships Figure 25.2

6 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 25.1: Phylogenies are based on common ancestries inferred from fossil, morphological, and molecular evidence

7 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Fossil Record Sedimentary rocks – Are the richest source of fossils – Are deposited into layers called strata Figure Rivers carry sediment to the ocean. Sedimentary rock layers containing fossils form on the ocean floor. 2 Over time, new strata are deposited, containing fossils from each time period. 3 As sea levels change and the seafloor is pushed upward, sedimentary rocks are exposed. Erosion reveals strata and fossils. Younger stratum with more recent fossils Older stratum with older fossils

8 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The fossil record – Is based on the sequence in which fossils have accumulated in such strata Fossils reveal – Ancestral characteristics that may have been lost over time

9 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Though sedimentary fossils are the most common – Paleontologists study a wide variety of fossils Figure 25.4a–g (a) Dinosaur bones being excavated from sandstone (g) Tusks of a 23,000-year-old mammoth, frozen whole in Siberian ice (e) Boy standing in a 150-million-year-old dinosaur track in Colorado (d) Casts of ammonites, about 375 million years old (f) Insects preserved whole in amber (b) Petrified tree in Arizona, about 190 million years old (c) Leaf fossil, about 40 million years old

10 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Morphological and Molecular Homologies In addition to fossil organisms – Phylogenetic history can be inferred from certain morphological and molecular similarities among living organisms In general, organisms that share very similar morphologies or similar DNA sequences – Are likely to be more closely related than organisms with vastly different structures or sequences

11 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sorting Homology from Analogy A potential misconception in constructing a phylogeny – Is similarity due to convergent evolution, called analogy, rather than shared ancestry

12 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Convergent evolution occurs when similar environmental pressures and natural selection – Produce similar (analogous) adaptations in organisms from different evolutionary lineages Figure 25.5

13 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 25.2: Phylogenetic systematics connects classification with evolutionary history Taxonomy – Is the ordered division of organisms into categories based on a set of characteristics used to assess similarities and differences

14 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Binomial Nomenclature Binomial nomenclature – Is the two-part format of the scientific name of an organism – Was developed by Carolus Linnaeus

15 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The binomial name of an organism or scientific epithet – Is latinized – Is the genus and species

16 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hierarchical Classification Linnaeus also introduced a system – For grouping species in increasingly broad categories Figure 25.8 Panthera pardus Panthera Felidae Carnivora Mammalia Chordata Animalia Eukarya Domain Kingdom Phylum Class Order Family Genus Species

17 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Linking Classification and Phylogeny Systematists depict evolutionary relationships – In branching phylogenetic trees Figure 25.9 Panthera pardus (leopard) Mephitis mephitis (striped skunk) Lutra lutra (European otter) Canis familiaris (domestic dog) Canis lupus (wolf) Panthera Mephitis Lutra Canis FelidaeMustelidaeCanidae Carnivora Order Family Genus Species

18 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Each branch point – Represents the divergence of two species Leopard Domestic cat Common ancestor

19 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Deeper branch points – Represent progressively greater amounts of divergence Leopard Domestic cat Common ancestor Wolf

20 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 25.3: Phylogenetic systematics informs the construction of phylogenetic trees based on shared characteristics A cladogram – Is a depiction of patterns of shared characteristics among taxa A clade within a cladogram – Is defined as a group of species that includes an ancestral species and all its descendants Cladistics – Is the study of resemblances among clades

21 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cladistics Clades – Can be nested within larger clades, but not all groupings or organisms qualify as clades

22 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A valid clade is monophyletic – Signifying that it consists of the ancestor species and all its descendants Figure 25.10a (a)Monophyletic. In this tree, grouping 1, consisting of the seven species B–H, is a monophyletic group, or clade. A mono- phyletic group is made up of an ancestral species (species B in this case) and all of its descendant species. Only monophyletic groups qualify as legitimate taxa derived from cladistics. Grouping 1 D C E G F B A J I K H

23 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A paraphyletic clade – Is a grouping that consists of an ancestral species and some, but not all, of the descendants Figure 25.10b (b)Paraphyletic. Grouping 2 does not meet the cladistic criterion: It is paraphyletic, which means that it consists of an ancestor (A in this case) and some, but not all, of that ancestors descendants. (Grouping 2 includes the descendants I, J, and K, but excludes B–H, which also descended from A.) D C E B G H F J I K A Grouping 2

24 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A polyphyletic grouping – Includes numerous types of organisms that lack a common ancestor Figure 25.10c (c)Polyphyletic. Grouping 3 also fails the cladistic test. It is polyphyletic, which means that it lacks the common ancestor of (A) the species in the group. Further- more, a valid taxon that includes the extant species G, H, J, and K would necessarily also contain D and E, which are also descended from A. D C B E G F H A J I K Grouping 3

25 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Shared Primitive and Shared Derived Characteristics In cladistic analysis – Clades are defined by their evolutionary novelties

26 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A shared primitive character – Is a homologous structure that predates the branching of a particular clade from other members of that clade – Is shared beyond the taxon we are trying to define

27 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A shared derived character – Is an evolutionary novelty unique to a particular clade

28 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Outgroups Systematists use a method called outgroup comparison – To differentiate between shared derived and shared primitive characteristics

29 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings As a basis of comparison we need to designate an outgroup – which is a species or group of species that is closely related to the ingroup, the various species we are studying Outgroup comparison – Is based on the assumption that homologies present in both the outgroup and ingroup must be primitive characters that predate the divergence of both groups from a common ancestor

30 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The outgroup comparison – Enables us to focus on just those characters that were derived at the various branch points in the evolution of a clade Figure 25.11a, b Salamander TAXA Turtle Leopard Tuna Lamprey Lancelet (outgroup) Hair Amniotic (shelled) egg Four walking legs Hinged jaws Vertebral column (backbone) Leopard Hair Amniotic egg Four walking legs Hinged jaws Vertebral column Turtle Salamander Tuna Lamprey Lancelet (outgroup) (a)Character table. A 0 indicates that a character is absent; a 1 indicates that a character is present. (b)Cladogram. Analyzing the distribution of these derived characters can provide insight into vertebrate phylogeny. CHARACTERS

31 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Phylogenetic Trees and Timing Any chronology represented by the branching pattern of a phylogenetic tree – Is relative rather than absolute in terms of representing the timing of divergences

32 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Phylograms In a phylogram – The length of a branch in a cladogram reflects the number of genetic changes that have taken place in a particular DNA or RNA sequence in that lineage Figure Drosophila Lancelet Amphibian Fish Bird Human Rat Mouse

33 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ultrametric Trees In an ultrametric tree – The branching pattern is the same as in a phylogram, but all the branches that can be traced from the common ancestor to the present are of equal length Figure Drosophila Lancelet Amphibian Fish Bird Human Rat Mouse Cenozoic Mesozoic Paleozoic Proterozoic Millions of years ago

34 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Maximum Parsimony and Maximum Likelihood Systematists – Can never be sure of finding the single best tree in a large data set – Narrow the possibilities by applying the principles of maximum parsimony and maximum likelihood

35 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 25.4: Much of an organisms evolutionary history is documented in its genome Comparing nucleic acids or other molecules to infer relatedness – Is a valuable tool for tracing organisms evolutionary history


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