Classification Chapter 18. Classifying Organisms.
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Transcript of Classification Chapter 18. Classifying Organisms.
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Classification
Chapter 18
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Classifying Organisms
• TAXONOMY is the study of how scientists classify organisms– The various levels of organization are called
TAXONS.
• Classification is a way for scientists to name and group organisms in an organized manner.
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Classifying Organisms (cont)
• Ancient philosophers used to classify organisms based off of visible characteristics, but as we have discovered more organisms, we have changed the system.
• Most of you are probably familiar with the system created by CAROLUS LINNAEUS, which is based off of different levels of organization.
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Classifying Organisms (cont)
LARGEST LEVEL
SMALLEST LEVEL
KingdomPhylum
ClassOrderFamilyGreenSpecies
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Classifying Organisms (cont)
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Classifying Organisms (cont)
• You can remember the order with the following sentence:
• Kings Play Cards On Fat Green Stools.
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Classifying Organisms (cont)
• All living things have two names usually from Latin that describes an essential trait. This process of giving all living things two name is called BINOMIAL NOMENCLATURE.
• Tips on naming organisms:– The first name is the genus and the second is the species– The whole name is italicized– Genus is capitalized
• Example: – Homo sapiens is the term for humans. Homo = man / same, sapiens
= wise
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Modern Classification
• While we still use the Linnaeus system and binomial nomenclature, there is one major difference in modern classification.
• ORGANISMS ARE CLASSIFIED ACCORDING TO THEIR PHYLOGENY, EVOLUTIONARY DESCENT, NOT JUST THEIR PHYSICAL APPEARANCE!!
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Modern Classification (cont)
• Evolutionary relationships are shown using CLADOGRAMS like this one.
• According to this cladogram, primates and rabbits shared a common ancestor more recently than primates did with sharks.
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According to this cladogram, which dinosaur is most closely related to modern birds?
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How do scientists determine evolutionary relation?
• Physical similarities• Fossil record• Embryology• Geographic evidence• Homologous, analogous, &
vestigial structures• Genetic similarities in DNA &
RNA
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Modern Classification (cont)
• Another difference with modern classification is that we have an added taxon: DOMAIN.
• There are three domains: BACTERIA, ARCHAEA, and EUKARYA.
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Bacteria
• Bacteria DO NOT have a nucleus
• Are unicellular
• Have cell walls
• Can be either autotrophs or heterotrophs
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Archaea
• Archaea DO NOT have a nucleus
• Live in extreme environments like volcanoes, hot geysers, depths of the oceans, etc
• Are unicellular
• Have cell walls
• Can be either autotrophs or heterotrophs
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Eukarya
• Have a nucleus
• Usually multicellular but occasionally unicellular
• Have four kingdoms:– Protista (autotroph or heterotroph)– Fungi (heterotroph)– Plantae (autotroph)– Animalia (heterotroph)
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Eukarya (cont)
Plantae Animalia
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Patterns of Evolution
• ADAPTIVE RADIATION: when one species branches off into numerous other species– Example: Darwin’s finches all evolved from
ONE species.
• CONVERGENT EVOLUTION: due to similar lifestyles, some organisms evolve similar adaptations.– Example: Sharks, penguins, and dolphins are
not closely related, BUT they all have flippers and pointed heads/beaks to be excellent swimmers.
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Patterns of Evolution (cont)
• CO-EVOLUTION: when two organisms evolve together– Example: Bees and flowers have evolved a mutual
relationship. Bees pollinate flowers and flowers provide bees with nectar to make honey.
• MASS EXTINCTION: occurs when a huge percentage of species dies out– Example: When a meteor struck Earth 65 mya, the
dust in the atmosphere blocked the sun, which killed most plants and, in turn, most animals.
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Patterns of Evolution (cont)
• GRADUALISM: slow, continued evolution– Example: Over millions of years, horse have become
larger.
• PUNCTUATED EQUILIBRIUM: this describes sudden bursts evolution– Example: A severe drought could kill all trees with
juicy fruit in a few years. As a result, the only surviving birds in that time would include those with small, hard beaks to eat tiny seeds.
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Gradualism vs. Punctuated Equilibrium