Essay on Biology I Honors Chapter 17

I.

Section 1: Biodiversity
investigates the variety of organisms considered at all levels from populations to ecosystems
A. Taxonomy the science of describing, naming, and classifying organisms 1. Taxon any particular group within a taxonomic system
2. Aristotle classified organisms into only two taxa: plants and animals. He grouped animals according to whether they lived on land, water, or air and grouped plants based on differences in their stems.
B. The Linnaean System
1. Carolus Linnaeus devised a system of grouping organisms into hierarchical categories according to their form and structure
2. Each category represents a level of grouping from larger, more general categories to smaller, more specific categories.
3. Original system had 7 levels.
4. Domain, Kingdom, Phylum, Class, Order, Family, Genus,
Species (D King Phillip Came Over From Geneva,
Switzerland)
C. Levels of Classification
1. Domain most general
2. Kingdom largest category
3. Phylum consists of classes
4. Class consists of orders
5. Order consists of families
6. Family consists of genus

7. Genus contains species
8. Species smallest group which contains only a single kind of organism 9. Binomial Nomenclature system of twopart names in which the genus name is followed by the species identifier
10. subspecies variations of a species that live in different geographic areas
II.

Milestones in Classifications of Organisms
A. 300 B.C. Theophrastus classifies 500 plants
1. Classified into herbs, shrubs, preshrubs, and trees
B. 1555 Gessner publishes
Historia Animalium
1. Categorized thousands of animals into quadrupeds, birds, fish, and snakes
C. 1650 Ray publishes
Historia Plantarum
1. Categorized thousands of plants based on visual similarities and differences
D. 1735 Linnaeus proposes taxonomic system
1. Categorized thousands of organisms into hierarchy starting with genus and species and building to a higher taxa including two kingdoms
E. 1866 Haeckel draws a “Tree of Life”
1. Redrew into 3 kingdoms
F. 19591969 Whittaker proposes fourkingdom and then fivekingdom system G. 1966 Hennig proposes cladistics

1. Classifies organisms based on their shared, derived traits in order to reflect their evolutionary history
H. 19771990 Woese names sixth names sixth kingdom and three domains 1. Divided the thenexisting kingdom Monera into 2 new kingdoms: Archaebacteria and Eubacteria
I. 2002 Discovery of Mantophasmatodea leads to a new order of insects III.

Section 2: Systematics
classifying organisms in terms of their natural relationships A. Phylogenetics analysis of the evolutionary or ancestral relationships among taxa
1. Phylogenetic diagram (phylogenetic tree) the form systematists represent their hypotheses. They may change whenever new discoveries and investigations cause scientists to revise their hypotheses.
2. Evidence of Shared Ancestry the fossil can help provide the framework of a phylogenetic diagram, but a systematists would test inferred relationships with additional evidence.
B. Cladistics a system of phylogenetic analysis that uses shared and derived characters as the only criteria for grouping taxa
1. Developed by German biologists Willi Hennig
2. shared character a feature that all members of a group have in common 3. derived character a feature that evolved only within the group under consideration
4. clade group of organisms that includes an ancestor plus all of its descendants
5. cladograms phylogenetic diagrams
6. Because cladistic analysis is comparative, the analysis deliberately includes an organism that is only distantly related to the other organisms. The organism is called an outgroup.
C. Molecular Cladistics
1. A biologist can count the shared, derived, amino acids at each position in a protein and construct a tree that hypothesizes relationships between various species
2. molecular clock a tool for

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