Classification

1. Classification Why do you think scientists like to put organisms into groups, like mammals or insects?

2. What is Classification? • Classification is the arrangement of organisms into orderly groups based on their similarities • Taxonomy is a classification based on differences and similarities in an organism’s characteristics • Taxonomists are scientists that identify & name organisms • Taxonomists classify organisms into groups called taxon

3. Why Classify? • Scientists have classified about 2 million species • However, there are many more organisms than we have found. • Estimates usually range from 3-10 million, but go as high as 50 million • That shows Earth has a tremendous amount of biodiversity(variety of organisms) • This is only 1-5% of all organisms that have ever lived!!!!!

4. Why Classify? • Accurately & uniformly names organisms • Prevents misnomers such as starfish & jellyfish that aren't really fish • Uses same language (Latin or some Greek) for all names Sea “horse”??

5. Confusion in Using Different Languages for Names

6. Latin Names are Understood by all Taxonomists

7. Early Taxonomists • 2000 years ago, Aristotle was the first taxonomist • Aristotle divided organisms into plants & animals • He subdivided them by their habitat ---land, sea, or air dwellers

8. Carolus Linnaeus: 1707 –1778 • 18th century taxonomist • Classified organisms by their structure • Developed naming system still used today

9. Carolus Linnaeus • Called the “Father of Taxonomy” • Developed the modern system of naming known as binomial nomenclature • Two-word naming system

10. Binomial nomenclature • Genus species • Latin or Greek • Capitalize genus, but NOT species • Underline when writing • Italicized in print American Robin

11. Binomial nomenclature • The International Code for Binomial Nomenclature contains the rules for naming organisms • All names must be approved by International Naming Congresses (International Zoological Congress) • This prevents duplicated names • Organisms are often named using descriptive words, like habitat or a physical characteristic OR sometimes using the person whom discovered them

12. Levels of Classification • The levels of classification are a hierarchy of groups (taxa) from broadest (domain) to most specific (species)

13. Levels of Classification • Domain • Kingdom • Phylum • Class • Order • Family • Genus • Species • Sometimes subspecies is added to the bottom of the list • Subspecies are the same species, but they live in different areas

14. Three Domain system • Classification is an ongoing process with many revisions • Currently, we have a three-domain system • Bacteria: the prokaryotic organisms we are familiar with • Archaea: “extreme” prokaryotic-like organisms that live in harsh conditions (i.e. at the vents of volcanoes at the bottom of the ocean floor) • Eukarya: more complex cellular organisms, with organelles (may be unicellular or multicellular)

15. King • Phillip • Came • Over • For • Good • Soup!

17. Systematics • Systematicsis a science whose goal is to classify organisms in terms of their natural relationships • Phylogenetics is the study of the evolutionary history of organisms • Uses phylogenetic trees to depict these relationships

18. Phylogenetics • The analysis of the evolutionary or ancestral relationships among taxa. • Classification is based on evolutionary relationships • Found by studying RNA, DNA, amino acids, homologous structures, and embryos (molecular systematics) • These relationships are often shown in a cladogram

19. Cladistics • Cladistics is the study of how organisms can be separated into groups with similar characteristics (clade) • A cladogram is a type of phylogenetic diagram using shared characteristics

20. Cladistics • Cladogram-A diagram showing how organisms are related based on shared, derived characteristics such as feathers, hair, or scales • Shared characters are features that ALL members of a group have in common. • For example, all organisms in the Domain Eukarya domain have true nuclei • Derived characters are features that evolved only in the group under consideration. • Feathers for example, are believed to have evolved only in the birds, not from a common ancestor that they have with reptiles.

21. Cladistics • Cladograms are organized into clades, which is an ancestor and all of its descendants. • Cladograms are not only based on physical features, they are also based on biomolecular similarities (like DNA, chromosomes and proteins) • Outgroups- have no shared characteristics with the other organisms in the diagram and are only distantly related (used as a basis of comparison)

22. Cladogram • Feathers are a derived characteristic in the birds • Hagfish are the outgroup • Jaws are a shared primitive characteristic between all organisms except the hagfish

24. Cladogram • Hair is a derived characteristic in leopards (on this cladogram, only leopards have hair) • NOTE-hair is a shared characteristic in the previous cladogram, so these characteristics can change based on the cladogram • Character tables may help you make cladograms

25. Other types of phylogenetic trees • Phylogram: this cladogram shows the number of changes in the DNA sequence • The longer you draw the branch, the more changes have occurred in the DNA • Ultrametric tree: shows the relative times of evolution from a common ancestor

26. How do we make a tree with so much data? • Because there are so many ways to organize species, there must be a systematic way to approach organization • Maximum parsimony: use the simplest explanation to determine organization (requires the fewest evolutionary events to become new species) • Maximum likelihood: what is the most likely relationship of organisms based on rates of evolution

27. Molecular clocks • Another tool to develop evolutionary relationships are molecular clocks (a way to measure time of evolutionary change based on the observation that some genes and regions of the genome appear to evolve at constant rates) • By examining the number of nucleotide differences over time, we can calculate a rate • Highly based on theory and extrapolation • The clock could be “upset” by natural selection

28. Dichotomous Keys • Used to identify organisms • "Dichotomous" means "divided into two parts". • Characteristics given in pairs • Read both characteristics and either go to another set of characteristics OR identify the organism

29. Dichotomous Keys • Always read both choices, even if the first seems to be the logical one at first. • Be sure you understand the meaning of the terms involved. Do Not Guess. • When measurements are given, use a calibrated scale. Do Not Guess. • Since living things are always somewhat variable, do not base your conclusion on a single observation. Study several specimens to be sure your specimen is typical. • If the choice is not clear, for whatever reason, try both divisions. If you end up with two possible answers, read descriptions of the two choices to help you decide

30. Dichotomous Keys 1. a. Bean round………..Garbanzo bean b. Bean elliptical or oblong…..Go to 2 2. a. Bean white…………White northern b. Bean has dark pigments……Go to 3 3. a. Bean solid in color…….Go to 4 b. Bean is spotted……..….Pinto bean 4. a. Bean black…………........Black bean b. Bean reddish-brown…….Kidney bean

31. Making Dichotomous Keys • Eliminate an organism in every step (one part leads to a name, the other part leads to another step) • Use measurements rather than terms like "large" and "small". • Try to make the choice a positive one -something "is" instead of "is not".

32. Making Dichotomous Keys - Continued • If possible, start both choices of a pair with the same word. • If possible, start different pairs of choices with different words. • Precede the descriptive terms with the name of the part to which they apply.(like legs are red instead of red legs)

33. DICHOTOMOUS KEY ASSIGNMENT • You will be creating your own dichotomous key • The subjects of the key will be the students in this class • Criteria must be high school appropriate and non-insulting