The document discusses several key aspects of speciation and taxonomy: 1) Speciation requires isolation of populations which then undergo genetic divergence and reproductive isolation. The main types of speciation discussed are allopatric and sympatric speciation. 2) Mechanisms of reproductive isolation that can lead to speciation include geographical, ecological, temporal, behavioral, mechanical and gametic isolation. 3) Polyploidy, where organisms have more than two paired sets of chromosomes, is another path to speciation discussed. 4) The document outlines the history of taxonomy from Aristotle to the current three domain system recognizing bacteria, archaea and eukarya based on genetic analysis.

1. The Origin of Species

2. Speciation I Requirements Isolation of populations Genetic divergence Speciation has seldom been observed in nature Allopatric speciation Sympatric speciation Ecological isolation Chromosomal aberrations Animals Plants

3. Speciation II Types of speciation Divergent speciation Phyletic speciation Models of speciation Gradualism Punctuated equilibrium

4. Allopatric Speciation Single species (white mice); homogeneous habitat Geographical barrier (impassable river); isolated populations Genetic drift; genetic divergence; tan vs white mice Barrier removed (river dries up); mix but don’t interbreed (a) (b) (c) (d)

5. Sympatric Speciation Single species (white mice); homogeneous habitat (a) Climate change; two habitats; isolated because don’t mix (b) Environmental pressure to adapt; genetic divergence; tan vs white mice (c) Sufficient divergence; now different species (d)

6. Isolation Mechanisms Premating Geographical isolation (too far away/barrier) Ecological isolation (bird vs. fish) Temporal isolation (different mating seasons) Behavioral isolation (courtship and rituals) Mechanical incompatibility (tab A can’t fit into slot B) Postmating Gametic incompatibility (sperm can’t fertilize) Hybrid inviability Hybrid infertility

7. Speciation by Polyploidy Diploid Gamete Meiosis Diploid Gametes Viable Tetraploid Zygote Viable Diploid Gametes Haploid Gamete Viable Triploid Zygote Meiosis (fails) Triploids can’t do meiosis; No viable gametes. Tetraploid Plant Tetraploid Plant Diploid Plant Meiosis Fertilization Meiosis Fertilization

8. Interpreting an Evolutionary Tree Lines that don't reach the top represent extinct species. Forks represent speciation events. Each line represents a species. Lines that reach the top represent existing species. Steeper slope represents slow phenotypic change. More horizontal slope represents rapid phenotypic change.

9. Systematics: Seeking Order Amidst Diversity

10. Taxonomic Principles Taxonomic categories form an increasingly inclusive, nested hierarchy “ D id K ing P hillip C ame O ver F or G ood S ___" to remember categories Domain, Kingdom, phylum (animals and protists) or division (plants, fungi, bacteria, and plant-like protists), class, order, family, genus, and species Domain - most inclusive Species - least inclusive Scientific name— Genus and species

11. Origins of Taxonomy Aristotle (384–322 B.C.) Simple classification Based on: Structural complexity Behavior Degree of development at birth Carolus Linnaeus (1707–1778) Based on resemblance to other life forms Established binomial nomenclature Charles Darwin (1809–1882) Categories reflect evolutionary relationship

12. The Changing Classification System Prior to 1970—two-kingdom system Plants and animals 1969—Roger Whittaker—five-kingdom system Monera, Protista, Fungi, Plantae, Animalia 1990—Carl Woese—three-domain system Bacteria, Archaea, Eukarya Discovered that kingdom Monera included two very distinct groups (Bacteria and Archaea) based on nucleotide sequences of ribosomal RNA

13. Problems concerning classification of species The biological species concept defines species as “groups of interbreeding natural populations, which are reproductively isolated from other such groups” Cannot be applied to asexually reproducing organisms The phylogenetic species concept defines a species as “the smallest diagnosable group that contains all the descendants of a single common ancestor” Can be applied to sexually and asexually reproducing organisms May eventually replace the biological species concept

14. Biodiversity How many species exist? 1.5 million species categorized Up to 30 million species may exist 7000 to 10,000 new species described/y Many classified species are becoming extinct as their habitats are destroyed

15. Microscopic Structures Help to Classify Organisms (a) (b) (c) Bristles on a marine worm “ Teeth” on a snail’s radula Shape and surface features on a pollen grain

16. Similarity of Human and Chimp Chromosomes H = Human C = Chimp

17. Modern Criteria for Classification Anatomy - homologous structures Developmental stages - embryology Biochemical similarities - use of genetic information

18. The Tree of Life

19. Representative Prokaryotes Vibrio cholerae of the domain Bacteria Methanococcus jannaschi of the domain Archaea

20. The Concept of Monophyly Monophyletic NOT Monophyletic (a) (b) (c) Reptiles not Monophyletic

21. Relatedness by DNA Sequences

22. The Origin of HIV Virus

23. The End