1. Chapter 18
Classification

2. Chapter 18 Mystery Page 509… GRIN AND BEAR IT
Hypothesis: Are polar bears and brown bears separate species?

3. Section 18.1 Finding Order in Diversity
Objectives:
What are the goals of binomal nomenclature and systematics?
How did Linnaeus group species into larger taxa?
Define:
Binomial nomenclature
Genus
Systematics
Taxon
Family
Order
Class
Phylum
Kingdom

4. I. Assigning Scientific Names
Groundhog
woodchuck
To understand diversity must describe and name each species
Each scientific name must refer to one and only one species
Everyone must use the same name for that species
Common names are confusing (mean different things in different countries)
Burro
Donkey
Gnus
Wildbeast
Bearded Antelope
Puma
Cougar
Mountain lion
panther

5. Assigned greek/latin names Describe species in great detail
18th century
Assigned greek/latin names
Describe species in great detail
Names can be long still confusing
Difficult to standardize b/c different scientists focused on different characteristics
Differences can be used to ID species using dichotomous key

6. A. Binomial Nomenclature
1730s – swedish botanist – Carolus Linnaeus – developed 2-word naming system
In binomial nomenclature, each species is assigned a 2-part scientific name.
Written in italic
First word begins w/ capital letter = genus to which org belongs
Genus – group of similar species
Second word is lowercased = unique to each species
Species – group of individuals capable of interbreeding and producing fertile offspring
Often description of important trait or habitat

7. B. Classifying Species into Larger Groups
Scientists try to classify (organize) living and fossil species into larger groups that have biological meaning
Systematics – science of naming and grouping organisms
The goal of systematics is to organize living things into groups that have biological meaning
Groups = taxa (singular = taxon)

9. Mystery Clue
Page 512…
Polar bears and brown bears interbreed and produce fertile hybrids in zoos, but they very rarely interbreed in nature.
What do you think this means about the relationship between them?

10. II. The Linnaean Classification System
Linnaeus developed classification system that organized species into taxa that formed a hierarchy (set of ordered ranks)
Original system = 4 levels
Over time, Linnaeus’s original classification system expanded to include seven hierarchial taxa: species, genus, family, order, class, phylum, and kingdom
2 smallest categories = genus & species
Grouped species according to anatomical similarities and differences  placed into larger groups
Example: Camelus bactrianus (Camel)
* Camelus = genus name
* bactrianus = species name
* Camelus dromedarius (different species in same genus  Camel with 1 hump)

11. 1. Family Group larger than genus
Multiple genuses can be classified in the same family
Example: Lama glama – South American llama
Resembles Bactrian camels and dromedaries
But more similar to other South American species than it is to European and Asian camels
So different genus: Lama
Several genera that share many similarities grouped into larger group (family)
Example: Camelidae

12. 2. Order
Closely related families grouped into next larger rank = Order
Example: Camels and llamas (family Camelidae)  grouped with several other animal families
deer – family Cervidae
cattle – family Bovidae
= order Artiodactyla (hoofed animlas with even number of toes)

13. 3. Class Similar orders grouped into next larger rank  class
Example: order Artiodactyla placed in class Mammalia
Includes all animals that are warmblooded, have body hair, and produce milk for their young

14. 4. Phylum Classes are grouped into a phylum
Includes orgs that are different but share impt characteristics
Example: class Mammalia grouped w/ Birds (class Aves), reptiles (class Reptilia), amphibians (class Amphibia), and all classes of fish into phylum Chrodata
All share impt body-plan features (nerve cord along back)

15. 5. Kingdom Largest and most inclusive taxonomic category
All multicellular animals are placed in kingdom Animalia

16. A. Problems with Traditional Classification
Members of a species determine which orgs belong to that species by deciding w/ whom they mate and produce offspring
Researchers define Linnaean ranks above the level of species b/c different groups have been defined in different ways at different times
How to determine which similarities and differences are most important?
Linnaeus chose characteristics carefully (century before Darwin)
Modern systematists apply Darwin’s ideas to classification and try to look beyond simple similarities and differences and look to evolutionary relationships
Today try to assign species to a larger group in ways that reflect how closely members of those groups are related to each other

18. Section 18.2 Modern Evolutionary Classification
Objectives:
What is the goal of evolutionary classification?
What is a cladogram?
How are DNA sequences used in classification?
Define:
Phylogeny
Clade
Monophyletic groups
Cladogram
Derived character

19. I. Evolutionary Classification
Phylogeny – the evolutionary history of lineages
The goal of phylogenic systematics, or evolutionary classification, is to group species into larger categories that reflect lines of evolutionary descent, rather than overall similarities and differences

20. A. Common Ancestors
Phylogenic systematics places orgs into higher taxa whose members are more closely related to one another than they are to members of any other group
The larger a taxon is, the farther back in time all of its members shared a common ancestor

21. B. Clades
Clade – group of species that includes a single common ancestor and all descendants of that ancestor (living and extinct)
Clade must by monophyletic group – includes single common ancestor and all of its descendants
Some groups defined before advent of evolutionary classification = monophyletic
Some groups = paraphyletic – the group includes common ancestor but excludes one or more groups of descendants

22. II. Cladograms
Cladistic analysis – compares carefully selected traits to determine order in which groups of organisms branched off from common ancestor
Cladogram – links groups of organisms together by showing how evolutionary lines (lineages) branched off from common ancestor

24. A. Building Cladograms
Speciation event – one ancestral species splits into 2 new species = basis of each branch point (node)
Node – represents last point at which the 2 new lineages shared a common ancestor
Node splits a lineage into 2 separate lines of evolutionary ancestry
Bottom (root) represents common ancestor shared by all orgs in cladogram
Branching patterns indicate degrees of relatedness among orgs

25. B. Derived Characters
Cladistic analysis focuses on certain kinds of characters (derived characters) when assigning orgs to clades
Derived character – trait that arose in most recent common ancestor of a particular lineage and was passed along to its descendants
Whether or not a character is derived depends on the level at which you’re grouping orgs
Example: several traits shared by coyotes and lions (clade Carnivora) (clade Tetrapoda-4 legs) (clade Mammalia-hair)

26. C. Losing Traits 4 limbs = derived character of clade Tetrapoda
Snakes (no limbs) but ancestors of snakes had 4 limbs
Trait for limbs was lost
Distantly related groups of orgs can sometimes lose the same character  systematists cautious about using absence of a trait as a character
Whales do no have 4 limbs either, but snakes more closely related to other reptiles than they are to whales

27. D. Interpreting Cladograms
Lowest node represents last common ancestor of all 4-limbed animals (clade Tetrapoda)
Forks show order in which various groups branched off from tetrapod lineage over course of evolution
Position of characters reflect order in which those characteristics arose in lineage
Derived characters that occur “lower” on cladogram than the branch point for a clade are not derived for that particular clade

28. E. Clades and Traditional Taxonomic Groups
True clad must be monophyletic – contains ancestral species and all of its descendants (can’t leave any out)
Also cannot include any species not descendants of original ancestor
Many traditional taxonomic groups do form valid clades
class Mammalia corresponds to clade Mammalia  all vertebrates w/ hair and other impt chars
Some traditional groups do not form valid clades
Today’s reptiles all descended from common ancestor
Birds also descended from same ancestor (not in class Reptilia)
Reptilia w/o birds is not a clade
Aves = bird clade
Dinosaura & Reptilia clades = reptiles + birds
Evolutionary biologists look for links b/w groups & how each is related to others
Bird = also dinosaur, reptile, tetrapod, chordate

30. III. DNA in Classification
Cladistic analysis based largely on physical chars: skeletons & teeth
Goal of systematics = understrand evolutionary relationships of all life on earth
Bacteria, plants, snails, apes
No physical similarities, so how can they be related??

31. A. Genes as Derived Characters
All orgs carry genetic info in DNA passed from earlier generations
Orgs share number of genes and show impt homologies used to determine evolutionary relationship
Example: eukaryotic cells have mitochondria & all mitochondria have their own genes
All genes mutate over time  shared genes contain differences that can be treated as derived characters in cladistic analysis
The more derived genetic characters 2 species share, the more recently they shared a common ancestor and the more closely they are related in evolutionary terms

32. B. New Techniques Suggest New Trees
Use of DNA characters helped make evolutionary trees more accurate
Example: African vulture vs. American vulture – look alike and traditionally classified as falcons
American vulture – urinates on legs when overheated  similar behavior to stork; not African vulture
Analysis of DNA: American vulture more similar to storks than African vultures
Suggests: American vultures and storks = more recent common ancestor than American and African vultures
Molecular analysis = powerful tool routinely used by taxonomists to supplement data from anatomy
Example: Giant panda & red panda
Share anatomical similarities w/ bears and raccoons
Peculiar wrist bones that work like a human thumb
DNA analysis = giant panda shares more recent common ancestor w/ bears than raccoons
DNA places red pandas outside bear clade in different clade that includes raccoons, seals, weasels

33. Mystery Clue
Page 522…
DNA comparisons show that some populations of brown bears are more closely related to polar bears than they are to other brown bears.
What do you think this means for the classification of polar bears?

34. Section 18.3 Building the Tree of Life
Objectives:
What are the six kingdoms of life as they are now identified?
What does the tree of life show?
Define:
Domain
Bacteria
Archea
Eukarya

35. I. Changing Ideas About Kingdoms
Linnaeus time – only differences among living things were fundamental chars that separated animals from plants
Animals = orgs that moved from place to place and used food for energy
Plants = green orgs that generally did not move and got energy from sun
Problem: Linnaeus’s 2 kingdoms did not reflect full diversity of life so classification system changed dramatically and still changing

36. A. Five Kingdoms
Single celled microorganisms significantly different from plants and animals
At first  all placed in one kingdom (Protista)
Then  yeasts, molds, mushrooms (Fungi)
Later  bacteria (no nuclei, mitochondria, chloroplasts = prokaryotes (Monera)
Single-celled eukaryotic orgs remained in Protista
5 Kingdoms: Monera, Protista, Fungi, Plantae, Animalia

37. B. Six Kingdoms
1990s – researchers learned a great deal about genetics and biochemistry of bacteria
Orgs in Monera = 2 genetically and biochemically different groups (Eubacteria & Archaebacteria)
The six-kingdom system of classification includes the kingdoms Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia

38. C. Three Domains
Genomic analysis revealed that 2 main prokaryotic groups are ever more different from each other and from eukaryotes than previously thought  new taxonomic category (domain)
Domain – larger, more inclusive category than kingdom
3 domains – Bacteria (kingdom Eubacteria), Archaea (kingdom Archaebacteria), Eukarya (kingdoms Fungi, Planta, Animalia, “Protista”)
“Protista” – paraphyletic group – not a true clade
no way to put all unicellular eukaryotes into clade that contains single common ancestor, all of its descendants, and only those descendants

39. II. The Tree of All Life
Goal – present all life on single evolutionary tree
Relationships studied  grouping changes & names of groups change
Cladograms = visual presentations of hypotheses about relationships (not hard and fast facts)
The tree of life shoes current hypotheses regarding evolutionary relationships among the taxa within the three domains of life

41. A. Domain Bacteria Unicellular Prokaryotic
Cells have thick, rigid walls that surround cell membrane
Cell walls contain peptidoglycan
Some photosynthesize and others don’t
Some need oxygen to survive and others are killed by oxygen
Corresponds to kingdom Eubacteria

42. B. Domain Archaea Unicellular Prokaryotic
Live in some of most extreme environments (volcanic hot springs, brine pools, black organic mud)
Many can survive only in absence of oxygen
Cell walls lack peptidoglycan
Cell membranes contain unusual lipids that are not found in any other orgs
Corresponds to kingdom Archaebacteria

43. C. Domain Eukarya Consists of all orgs that have nucleus
4 major groups: “Protista,” Fungi, Plantae, Animalia

44. The “Protists”: Unicellular Eukaryotes
Paraphyletic group
Current cladistic analysis divides into at least 5 clades
Each group of “eukaryotes formerly known as protists” is separate & each shares closest common ancestor with other groups rather than with each other.
Most unicellular
1 group – brown algae = multicellular
Some photosynthetic & others heterotrophic
Some display characters that most closely resemble those of plants, fungi, or animals

45. 2. Fungi Heterotrophs Cell walls containing chitin
Feed on dead or decaying organic material
Secrete digestive enzymes into food  breaks down into smaller molecules  absorb small molecules into bodies
Some multicellular (mushrooms)
Some unicellular (yeasts)

46. 3. Plantae Autotrophs Cell walls contain cellulose
Conduct photosynthesis using chlorophyll
Sister group to red algae (protists)
Includes green algae, mosses, ferns, cone-bearing plants & flowering plants

47. 4. Animalia Multicellular Heterotrophic No cell walls
Most can move about (some for only part of life cycle)
Incredible diversity
Many species of animals exist in nearly every part of planet

48. Solve the Chapter Mystery
Page 533…
List the evidence that supports classifying polar bears and brown bears into two different species. Then list the evidence that indicates that polar bears and brown bears belong to the same species
What evidence indicates that different populations of brown bears belong to different clades?
Do you think that the classic definition of species – “a group of similar organisms that can breed and produce fertile offspring” – is still adequate? Why or why not?