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Chapter 18 Classification

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1 Chapter 18 Classification

2 18-1 Finding Order in Diversity
Why Classify Organisms?? Biologists use classification systems to name organisms and group them in a logical order Taxonomy: Scientists classify organisms and assign each organism a universally accepted name

3 18-1 Assigning Scientific Names
For many species, there are often regional differences in their common names EX: Buzzard in the UK refers to a hawk, Buzzard in the US refers to a vulture To eliminate such confusion, scientists agreed to use a single name for each species

4 18-1 Assigning Scientific Names
Binomial Nomenclature: Scientists assign each kind of organism a universally accepted name in the system Two word system using the Genus and Species Words are always written in italics First word (Genus) is capitalized and second word (Species) is lowercase Second word is a Latinized description of a particular trait Developed by an 18th C. Swedish botanist named Carolus Linnaeus EX: Grizzly Bear = Ursus arctos

5 18-1 Assigning Scientific Names
Differences in Binomial Nomenclature: 1st part of scientific name is genus to which the organism belongs A genus is composed of a number of related species 2nd part of scientific name is unique to the species within the genus EX: Ursus arctos= Grizzly Bear, Ursus maritimus= Polar Bear EX: Papio annubis and Papio cynocephalus do NOT belong to the same species since the species part of the name is different. However, they do belong to the same genus

6 18-1 Assigning Scientific Names
Differences in Binomial Nomenclature Cont…: Bionomial, two-part, names are much shorter than the original naming system used detailed These names described detailed physical characteristics of a species They were problematic because they were very long and difficult to standardize EX: Oak with deeply divided leaves that have no hair on their undersides and no teeth along their ridges

7 18-1 Assigning Scientific Names
Linnaeus’s System of Classification: Based on Taxonomy naming system Taxonomy: a group at any level of an organization is referred to as a taxon Is hierarchical and consists of 7 taxonomic categories From largest to smallest: Kingdom (King)= Made up of phylums Phylum (Phillip) = Made up of several different classes Class (Came) = Made up of several different orders Order (Over) = Made up of several different families Family (For) = Made up of several different genuses Genus (Good) = Made up of several different species Species (Soup) Know classification order above.

8 18-1 Assigning Scientific Names
Examples of Taxonomic Levels: The most general and largest of Linnaeus’s system is the Kingdom Linnaeus recognized the kingdoms of plants (Plantae) and animals (Animalia) The class of Mammalia includes mammals which are organisms that have: Are warm-blooded Have body hair Produce milk for their young

9 18-2 Modern Evolutionary Classification
Traditional classifications like Linnaeus’s tended to take into account primarily general similarities in appearance However, some organisms that ARE NOT closely related look alike because of convergent evolution! Evolutionary Classification: The procedure of grouping organisms based on their evolutionary history Species within one genus should be more closely related to each other than a species in another genus All genera within a family share a common ancestor. Similar genes

10 18-2 Modern Evolutionary Classification
Derived Characters: An evolutionary innovation EX: Free swimming larva, segmented body Cladistic Analysis: Analysis that focuses on the order in which derived characters appear in an organism Looks only at derived characters, or those characteristics that are evolutionary innovations (EX: body structures, adaptations) New characteristics emerge as lineages evolve over time Cladogram: a table analyzing derived characters that shows the evolutionary relationship between organisms Helps scientists understand how lineages branched from one another in the course of evolution Shows the order in which derived characters evolved

11 18-2 Modern Evolutionary Classification
Similarities in RNA and DNA: Similar genes are evidence of common ancestry Similarities in DNA can help determine classification and evolutionary relationships EX: A cow and a yeast’s degree of relationship can be determined from their genes EX: Scientists have found that humans and yeast have similar genes for the assembly of certain proteins (Myosin) All organisms use DNA and RNA to pass on information

12 18-2 Modern Evolutionary Classification
Similarities in RNA and DNA Cont…: DNA evidence can help show the evolutionary relationship between organisms and how species have changed EX: Presence of similar genes in very dissimilar organisms implies that the organisms share a common ancestor like vultures and storks!

13 18-2 Modern Evolutionary Classification
Molecular Clocks: Uses DNA comparisons to estimate the amount of time that species have been evolving independently Main idea is that neutral mutations (mutations that have neither a positive or negative effect) accumulate at a steady rate DNA comparisons in 2 species can compare how dissimilar the genes are This dissimilarity indicates how long ago the 2 species shared a common ancestor

14 18-3 Kingdoms and Domains In the 1800’s scientists used a 3 kingdom classification system: Animals, Plants, Protista Scientists grouped organisms according to how long they have been evolving independently Biologists knowledge of diversity of life continued to grow We now know there are 6 Kingdoms: Protista (used to be grouped with Plants) Fungi Plantae Animalia Eubcteria (used to be grouped as the Monera category) Archaebacteria (used to be grouped as the Monera category)

15 18-3 Kingdoms and Domains The Three Domain System:
Modern analysis of evolutionary trees have given rise to a new taxonomic category– Domain A domain is more inclusive and larger than a kingdom There are 3 Domains: Eukarya: includes kingdoms protist, fungi, plants, & animals Archaea: includes kingdom Archaebacteria Bacteria: Includes kingdom Eubacteria The 3 domains are thought to have diverged from a common ancestor before the evolution of the main groups of eukaryotes Recognizes fundamental differences between 2 groups of prokaryotes- Bacteria & Archaea

16 18-3 Kingdoms and Domains Domain Bacteria: Domain Archaea: Unicellular
Cell walls are thick & rigid & contain peptidoglycan Corresponds to the kingdom Eubacteria Some need oxygen to survive & others do not Domain Archaea: Found in extreme environments-- volcanic hot springs, brine pools and mud without oxygen Cell membranes contain unusual lipids Corresponds to the kingdom Archaebacteria

17 18-3 Kingdoms and Domains Domain Eukarya: Protista:
Consists of all eukaryotes (cells with a nucleus Consists of the 4 kingdoms: Protista: organisms that cannot be classified as plants, animals, or fungi Usually single-celled EX: Algae Scientists argue that protista should be broken into several kingdoms because they are very diverse organisms that do not fit into other kingdoms

18 18-3 Kingdoms and Domains Kingdom Fungi: Kingdom Plantae:
Heterotrophs that feed on dead or decaying matter. Can be single or multicelled Cell walls contain chitin EX: Mushrooms & yeast Kingdom Plantae: Photosynthetic autotrophs Undergo photosynthesis Cell walls contain cellulose EX: mosses, ferns, flowering plants, cone-bearing plants, etc…

19 18-3 Kingdoms and Domains Animalia: Multicellular & heterotrophic
No cell walls Can move about EX: animals

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