modern evolutionary classification section 17-2. problems with traditional classification...
Post on 24-Dec-2015
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Problems with Traditional Classification
• Originally, organisms were grouped according to their physical features.
• Biologists now group organisms into categories based on their evolutionary history, not just physical similarities.
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How are evolutionary relationships determined?
• Structural similarities• Geographical distribution• Biochemistry
– Similar DNA and proteins
• Chromosome comparison– # and structure of chromosomes
• Breeding behavior– Ex. Different calls keep mates from within same group
• Embryonic development
Phylogeny
• What is it?– The evolutionary history of a species
• How is it shown?– Using models called phylogenetic trees
Cladistics
• A system of classification based on phylogeny
• It classifies organisms according to the order that they diverged from a common ancestor.
Cladistics
• Scientists look at ancestral characters, those found in the entire line of descent
• They also identify a group’s derived traits (unique inherited characteristics not found in a common ancestor) and use them to construct a branching diagram called a cladogram, a model of the phylogeny of a species.
How does a cladogram work?
• 2 groups on diverging branches probably share a more recent common ancestor than those groups farther away.
• They show a probable evolution of a group of organisms from ancestral groups.
Kingdom Archaebacteria
• Prokaryotic– Unicellular– No membrane-bound nuclei
• Most live in harsh environments– Swamps, deep-ocean vents, etc.– Mostly no oxygen (anaerobic)
Kingdom Eubacteria
• Prokaryotic
• ~5000 species
• Very strong cell walls
• Live in most habitats, except extreme
• Some causes diseases, most are harmless
Kingdom Protista
• Eukaryotic
• Lacks complex organ systems
• Lives in moist environments
• Some unicellular, some multicellular
• Example: kelp
Kingdom Fungi
• Eukaryotic
• Heterotrophic—absorbs nutrients from organic materials in the environment
• Immobile (unmoving)
• Unicellular or multicellular
• Over 50,000 species
Kingdom Plantae
• Eukaryotic
• Multicellular
• Photosynthetic
• Immobile
• Cells tissues organs organ systems
• Over 250,000 species
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