Understanding Biological Classification: A Journey Through Taxonomy and Evolution

1. Classification 18.1 Finding Order in Diversity

2. Why Classify? • To study the diversity of life, biologists use a classification system to name organisms and group them in a logical manner. • Taxonomy

3. Assigning Scientific Names • Common names can be confusing and vary between regions. • Scientists agreed to use Latin and Greek when assigning scientific names to organisms. • This practice is still followed today as new organisms are discovered.

4. Binomial Nomenclature • Two-word naming system used in differentiating a species • Genus species • A genus is a group of related species. • Ursusarctos • Ursusmaritimus

5. Linnaeus's System of Classification • Includes seven levels- from smallest to largest • Species, Genus, Family, Order, Class, Phylum, Kingdom • Each level is called a taxon.

6. Linnaeus's System of Classification • Family • Genera that share many characteristics • Ursidae • UrsidaeUrsusarctos • UrsidaeUrsusmaritimus • UrsidaeAiluropodamelanoleuca

7. Linnaeus's System of Classification • Order • Broad taxanomic category composed of similar families • Carnivora • Examples: • Canidae • Felidae • Ursidae

8. Linnaeus's System of Classification • Class • Composed of similar orders • Mammalia • Includes animals that are warm blooded, have body hair, and produce milk for their young.

9. Linnaeus's System of Classification • Phylum • Includes many different organisms that share important characteristics • Chordata • Mammalia • Aves • Reptilia • Amphibia • Several classes of fish

10. Linnaeus's System of Classification • Kingdom • Largest and most inclusive level • Linnaeus started with only 2- Animals & Plants • Now, we recognize 6! • Plants, Animals, Protists, Fungi, Archaebacteria, Eubacteria.

11. Classification 18.2 Modern Evolutionary Classification

12. Which Similarities Are Most Important? • Organisms determine who belongs in their species by choosing whom they mate with! • Scientists have “invented” larger taxa according to an organisms characteristics.

14. Evolutionary Classification • Strategy of grouping organisms together based on their evolutionary history • Phylogeny- evolutionary relationships among organisms • See Figure 18-7

15. Evolutionary Classification • Organisms that appear very similar may NOT, in fact, share a common ancestor. • Because… natural selection operating on species in similar ecological environments has often caused convergent evolution.

16. Classification Using Cladograms • Only identifies and considers characteristics of organisms that are evolutionary innovations • New characteristics that arise as lineages evolve over time • Derived Characters- appear in recent parts of a lineage but not in its older members. • Can be used to construct a cladogram

17. Cladograms • Diagram that shows the evolutionary relationships among a group of organisms • Useful for helping scientists understand how one lineage branched from another in the course of evolution • Like a “Family Tree”

18. Similarities in DNA & RNA • All organisms have DNA to pass on to future generations. • The genes of many organisms show important similarities at the molecular level. • Similarities in DNA can be used to help determine classification.

19. Molecular Clocks • Comparison of DNA can be used to mark the passage the time that two species have been separated on the “family tree” • The degree to which genes are dissimilar indicates how far in the past the two species shared a common ancestor.

20. Classification 18.3 Kingdoms & Domains

21. The Tree of Life Evolves • All science adapts to new discoveries. • In the early days of classification Linnaeus proposed a 2-kingdom system. • Today, because of new discoveries, we recognize a six-kingdom system of classification.

22. The Three-Domain System • Molecular clock model analysis has given rise to a new taxonomic category larger than the kingdoms. • Domains

23. Domain Bacteria • Unicellular • Prokaryotic • Thick, rigid cell walls • Have peptidoglycan • Corresponds with the kingdom Eubacteria • Ecologically diverse • Some need oxygen • Some photosynthesize • Some are free-living • Some are parasites

24. Domain Archaea • Unicellular • Prokaryotic • Cell walls • No peptidoglycan • Unique lipids • Extremophiles • Hot springs • Brine pools • Anaerobic mud

25. Domain Eukarya • Kingdom Protista • Cannot be classified as animals, plants or fungi • Most diverse kingdom • Most unicellular • Except multicellular algae • Autotrophs or Heterotrophs • Some share characteristics with plants, some with fungi and some with animals.

26. Domain Eukarya • Kingdom Fungi • Heterotrophs • Feed on decaying organic matter • Secrete a digestive enzyme and absorb their food • Multicellular • Mushrooms • Unicellular • Yeast

27. Domain Eukarya • Kingdom Plantae • Multicellular • Photosynthetic autotrophs • Nonmotile • Cell walls with cellulose • Includes mosses, ferns, cone-bearing and flowering plants

28. Domain Eukarya • Kingdom Animalia • Multicellular • Heterotrophic • No cell walls • Very diverse group