classification of living things chapter 18. why classify classification is used to name organisms...
TRANSCRIPT
Classification of Living Things
Chapter 18
Why Classify
• Classification is used to name organisms and group them in a logical manner – Biologists have classified and named over 1.5
million species– Estimate that 2 million- 100 million have yet to be
discovered
Taxonomy• A branch of biology where scientists classify
organisms and assign each a universally accepted name
Taxonomy• A good classification system puts organisms in
groups with other organisms that are similar– Originally based on physical characteristics
• Physical traits are shared amongst unrelated organisms– Convergent evolution• Shark vs. dolphin• Bird vs. bat
Common Names
• Organism were originally referred to by common names– Names that are unique to a small group of people
• With out discussion; draw what comes to mind when you hear the word: cat
Use of common names• Common names can be misleading– Given based on physical characteristics and what
the organism reminds us of
jellyFISHseaHORSE
Sea CUCUMBER
Use of common names
• Common names vary among languages and even regions in the same country
–Mountain lion–Puma–Cougar–Panther
Use of common names
• Different species sometimes share a common name– What is a buzzard???
United States-Vulture
United Kingdom (England)-Hawk
Removing Confusion
• First Naming system – scientists used detailed physical descriptions • Names were long and hard to remember
• Carolus Linnaeus (mid 18th century)– Developed a two word naming system called
Binomial nomenclature • shows ancestral relation
Binomial Nomenclature
• scientific names are used to avoid confusion– Universally accepted
Cathartes aura Buteo jamaicensis
Taxonomic Nomenclature
KingdomPhylum
ClassOrderFamilyGenus
Species
Kids PreferCandyOverFried
Green Spinach
Hierarchical system (consists of levels)Each level is a taxon
Kingdom- AnimaliaPhylum- Chordata
Class- MammaliaOrder- Carnivora
Family- FelidaeGenus- Panthera
Species- leo
Binomial Nomenclature
Rules to follow1. Always written in italics (or underlined)2. First word is capitalized (genus name)3. Second word is lowercased (species name)
Binomial Nomenclature
• Genus a group of closely related speciesUrsus
Binomial Nomenclature
• Species a group of similar organisms that can breed
and produce fertile offspring
Ursus Ursus Ursusarctos maritimus americanis
Modern Evolutionary Classification
18.2
Modern Evolutionary classification
• Taxonomic groups are invented by scientist to group organisms with similar characteristics
Which Similarities are most important
• Taxonomists try to group organisms according to biologically important characteristics– Linnaeus grouped species based on visible
similarities (Dolphin example: Fish vs. Mammal)
Barnacle crab limpet
Evolutionary ClassificationLimpet and barnacle larvae
are very different.• Barnacles have jointed
limbs, Limpets DON’T !• Barnacles have a
segmented body, Limpets DON’T !
• Barnacles have an exoskeleton that molts, Limpets DON’T !
Crab and barnacle larvae are very similar
• Barnacles have jointed limbs, So do CRABS !
• Barnacles have a segmented body, So do CRABS !
• Barnacles have an exoskeleton that molts, So do CRABS !
Evolutionary Classification
Evolutionary Classification
• Organisms are grouped together based on evolutionary decent not just physical traits (WHY??)
• The higher the level of the taxon, the further back in time is the common ancestor
Lion• Kingdom: Animalia • Phylum: Chordata • Class: Mammalia • Order: Carnivora • Family: Felidae • Genus: Panthera • Species: leo
Tiger• Kingdom: Animalia • Phylum: Chordata • Class: Mammalia • Order: Carnivora • Family: Felidae • Genus: Panthera • Species: tigris
Lion• Kingdom: Animalia • Phylum: Chordata • Class: Mammalia • Order: Carnivora • Family: Felidae • Genus: Panthera • Species: leo
Grey Wolf• Kingdom: Animalia• Phylum: Chordata • Class: Mammalia • Order: Carnivora • Family: Canidae • Genus: Canis • Species: C. lupus
Cladistic analysis• Cladogram: a diagram
used to show evolutionary relationships
• A way of classifying organisms using only new evolutionary characteristics• Derived characteristics-
These characteristics appear in later organisms but not earlier ones
Molecular Clock
• Used to compare DNA of organisms– The more similar the DNA the more recently the
organisms branched off from one another• Neutral Mutations- are not affected by natural
selection– Accumulate in the DNA over time (at the same
rate in all species)
Cladogram
• Help us to understand how one lineage branched from another in the course of evolution. (family tree)
1. ______ Wings2. ______ 6 Legs3. ______ Segmented Body4. ______ Double set of wings
5. ______ Jumping Legs6. ______ Crushing mouthparts7. ______ Legs8. ______ Curly Antennae
Answer
1. ___F___ Wings2. ___C___ 6 Legs3. ___A___ Segmented Body4. ___G___ Double set of wings5. ___E___ Jumping Legs6. ___D___ Crushing mouthparts7. ___B___ Legs8. ___H___ Curly Antennae
Kingdoms and Domains
The tree of Live “Evolves”
Changes in the classification system
• New biological understanding lead to a more accurate classification system
• Genes show important similarities at the molecular level– Linnaeu’s didn’t know about DNA
• DNA from organisms can be sequenced and compared to show evolutionary relationships.
Molecular Clocks
• DNA comparisons can be used to estimate how long 2 species have been evolving independently.
• Mutations in the genes accumulate at different rates– The more similar mutations 2 species have the
closer related they are
Effect on Classification
• Scientist used to believe there were just 2 groups of living things: plants and animals
• 2 kingdom system doesn’t adequately represent diversity of life
• 6 kingdom system: – Eubacteria– Archaebacteria– Protista– Fungi– Plantae– Animalia
Eubacteria• Prokaryote• Unicellular• Autotroph or Heterotroph• Cell wall with peptidoglycan (extra outer layer)• Ecologically diverse (Common Bacteria)– Free-living soil organisms– Parasites– Photosynthetic– Anaerobic– aerobic
Archaebacteria
• Prokaryote• Unicellular• Autotroph or Heterotroph• Cell wall without peptidoglycan layer• Live in the most extreme environments (first
living organisms)– Volcanic hot springs– Brine pools– Black organic mud (NO oxygen)
Protista
• Eukaryote• Most are unicellular• Autotroph or Heterotroph• Cell walls of cellulose• Some have chloroplasts• Made up of organisms that cannot be classified elsewhere
Fungi
• Eukaryote• Most are Multicellular
(some unicellular)• Heterotrophs– Feed on dead or
decaying matter– Secrete digestive
enzymes to break down food
• Cell wall of chitin
Plantae
• Eukaryote• Multicellular• Autotroph– Carry out photosynthesis
• Chloroplasts• Cell wall of cellulose• Non-motile (cannot
move from place to place)
Animalia
• Eukaryote• Multicellular• Heterotroph• No cell wall• Most can move (at least
at some point in there life cycle)
• Very diverse group– Species that exist in almost
every part of the planet
3 Domain System
• Molecular clock analysis allows scientists to group organisms according to how long they have been evolving independently
• The domain is a more inclusive category than any other
• 3 Domains: Bacteria, Archaea, and Eukarya
Domain/ Kingdom Relationship