Classification. Why do we classify things? Finding Order in Diversity Classification provides scientists and students a way to sort and group organisms for easier study. Taxonomy – branch of biology that deals with the classification and naming of living things
Grouping organisms based on comparing characteristics makes it easer to study the diversity of live.
Binomial Nomenclature – 2 word system of identifying each kind of organism; avoids confusion
A. Carolus Linnaeus – founder of modern taxonomy; used structural similarities as a basis for his classification system
Why do biologists consider Linnaeus’s system an improvement over earlier systems?
Linnaeus’s Classification System – hierarchical system from most inclusive to least inclusive are:
This illustration shows how a grizzly bear, Ursusarctos, is grouped within each taxonomic category.
Linnaeus’s system was limited because similarities and differences were mainly visible
What was invented that helped to change the way scientists classify organisms?
Classifying species based on easily observed adult traits can pose problems. Which of these organisms seem most alike?
Behavioral – similar behaviors may indicate a close relationship – Fig. 18-8
American and African vultures look very much alike and were once classified together. American vultures have a peculiar behavior: When they get overheated, they urinate on their legs to cool down. The stork is the only other bird known to behave this way.
Biochemical – information about DNA, RNA & proteins can be used to help determine relationships and can be used to estimate how long different species have been separated
African Vulture American Vulture Wood Stork
Cytological – cellular structure – ex. Prokaryotic vs. eukaryotic, plant cell vs. animal cell
Embryological – early stages of development may show shared characteristics that are absent at the adult stages (Fig. 15-17 pg. 385)
Fossil Formation – establish relationships between modern-day species & those that lived years ago
Arranging the diversity of life into the highest taxa is a work in progress. What is important to understand is that new information has reopened issues concerning biological diversity. Fig. 18-11
Domains – the most inclusive categories, assigns more significance to the ancient evolutionary split between bacteria and archaea
peptidoglycan, most live in very extreme habitats
that are devoid of oxygen
Protista – Eukaryote, cell walls of cellulose in some; some have chloroplasts; most unicellular, some colonial, some multicellular
Animalia – Eukaryote, no cell walls or chloroplasts, multicellular, heterotroph