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