Biology - Chp 18 - Classification - PowerPoint
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Transcript of Biology - Chp 18 - Classification - PowerPoint
Chapter 18
Classification
18 – 1 Finding Order in Diversity
• Evolution has lead to a staggering variety or organisms
• Biologists have identified and named about 1.5 million species so far
• They estimate anywhere between 2 and 100 million additional species have yet to be discovered
Taxonomy
• The science of classifying and naming organisms
Assigning Scientific Names
• By the 18th century, European scientists recognized that referring to organisms by common names was confusing
• Common names vary among regions within a country
Mountain Lion
Cougar
Puma
Panther
Early Efforts at Naming Organisms
• First attempts at standard scientific names often described physical characteristics
• As a result, these names could be 20 words long!
• Ex.) The English translation of the scientific name of a particular tree might be “Oak with deeply divided leaves that have no hairs on their undersides and no teeth around their edges.”
Binomial Nomenclature• Carolus Linnaeus (18th Century)
• Swedish Botanist
• Developed a system for naming organisms
Binomial Nomenclature
• Two word naming system
Rules for Binomial Nomenclature
• Written in italics• First word is capitalized• Second word is lowercased
Ex.)
Genus species
Genus species
G. species
• The name often tells you something about the species
• Ex.) Tyranosaurus Rex
• Tyrant Lizard King
Taxon (taxonomic category)
• A group or level of organization
Linnaeus’s system of classification uses seven taxonomic categories
Kingdom
Phylum
Class
Order
Family
Genus
species
Largest / Least Specific
Smallest / Most Specific
Mnemonic DeviceKingdom
Phylum
Class
Order
Family
Genus
species
• King
• Phillip
• Came
• Over
• For
• Good
• Soup
18 -2 Modern Evolutionary Classification
Problems with Traditional Classification
• Sometimes, due to convergent Evolution organisms that are quite different from each other evolve similar body structures
• Ex.) Crab, limpet, barnacle
Evolutionary Classification • Darwin’s theory of evolution
changed the entire way that biologists thought about classification
• Biologists now group organisms into categories that represent lines of evolutionary descent, not just physical similarities
Classification Using Cladograms
• Many biologists now prefer a method called cladistic analysis
• This method of classification identifies and considers only those characteristics that arise as lineages evolve over time
Derived characteristics
• Characteristics that appear in recent parts of a lineage but not in its older members
Cladograms• Diagram that shows the
evolutionary relationships among a group of organisms
Similarities in DNA and RNA• Suppose you were trying to compare
diverse organisms such as yeast and humans
• It wouldn’t make sense to try to classify anatomical similarities
• The genes of many organisms show important similarities at the molecular level
• These similarities can be used as criteria to help determine classification
• Ex.) Myosin in humans & yeast
Molecular Clocks• Use DNA comparison to estimate
the length of time that two species have been evolving independently
Molecular Clocks• Mutations happen all the time at about
the same rate• A comparison of DNA sequences in
two species can reveal how dissimilar the genes are
• The degree of dissimilarity is an indication of how long ago the two species shared a common ancestor
18 -3 Kingdoms and Domains
• In taxonomy, as in all areas of science, ideas and models change as new information arises, some explanations have been discarded altogether, whereas others such as Darwin’s theory of evolution by natural selection, have been upheld
• So it should not be surprising that since the 1800’s, the tree of life has been revised and edited since the discovery of all this new information
The Tree of Life Evolves
• Before Linnaeus’s time, the only two Kingdoms that existed were Plants and Animals
• As scientists discovered new organisms that didn’t fit into the plant or animal category, they made a new category
The Old 5 Kingdom System
1. Animals
2. Plants
3. Fungi
4. Protist
5. Bacteria
• In recent years, as evidence about microorganisms continued to accumulate, biologists come to recognize that the Monera were composed of two distinct groups
The New 6 Kingdom System
1. Animals
2. Plants
3. Fungi
4. Protist
5. Eubacteria
6. Archaebacteria
The Three Domain System
• Molecular analysis has given rise to a new taxonomic category that is now recognized by many scientists
Domain
• Larger than a kingdom
3 Domains1. Bacteria• Eubacteria
2. Archaea• Archaebacteria
3. Eukarya• Protists, fungi, plants, animals
(Everything with a nucleus)
Domain Bacteria• Unicellular• Prokaryotic - no nucleus, no membrane
bound organelles• Thick walls (containing peptigoglycan)• Free living and parasitic• Important decomposers• Some photosynthesize• Some don’t need oxygen
– Anerobic
• Some need oxygen– Aerobic
Petri dish
Agar
Bacteria Colonies
What is this used for?
Domain Archaea
• Unicellular• Small• Prokaryotic• Live in extreme environments
Ex.) volcanic hotsprings, brine pools, black organic mud without oxygen
• Acidophiles – live in acidic environments
• Thermophiles – can tolerate hot temperatures 50 – 110 degrees
• Halophiles – can stand extreme concentrations of NaCl
• Methanogens – Produce methane CO2 + H CH4
Acidophiles
Thermophile
Halophile
Domain Eukarya• Consists of all organisms that
have a nucleus
Protista• Small
• Mostly unicellular
• Eukaryotic – has a nucleus, and membrane bound organelles
• Cannot be classified as animals, plants or fungi, but share many characteristics with plants, animals and fungi
Plant like Protists• Algae
• Photosynthetic – can make their own food
Euglenas
Flagella
Diatoms
Dinoflagellates
Dinoflagellates• Red tide
Green Algae
Red Algae
Brown Algae
Animal like Protists• Protozoans
• Heterotrophic – can’t make their own food
Fungus like Protists• Slime molds, water molds
• Decompose their food
Fungi• Mostly multicellular
Ex.) Mushroom, yeast
• Cell walls
Fungi• Heterotrophs
• Feed on decaying organic matter
• Secrete digestive enzymes into food source then
• Spread and reproduce by spores
Spores• Reproductive cells that form new
organisms without fertilization
Many are used in medicine
• Antibiotics
• Anti rejection
• Anti viral
Penicillium
Plantae• Multicellular
• Photosynthetic autotrophs – make their own food by photosynthesis
• Non-motile
• Cell walls (cellulose)
Animalia• Multicellular
• Heterotrophic
• No cell walls
• Most move
• Incredible diversity