1. Bianca Hernandez Biology Honors P6 11 April 2014
Ch.18 Classification
Bianca Hernandez
Biology Honors P6
11 April 2014

2. Think about it
Scientists have been trying to identify, name, and find order in our diverse earth for a long time, which has led us to classification.

3. 18.1 Finding Order in diversity
Key Questions
What are the goals of binomial nomenclature and systematics?
How did Linnaeus group species into larger taxa?
18.1 Finding Order in diversity

4. ASSIGNING SCIENTIFIC NAMES
1) understanding + studying diversity
describe and name each species, which is useful b/c if we refer to each species by one name only, everyone will use the name
what type of name?
Sometimes be misinterpreted b/c variations in languages and places , which leads to different species sharing common names
18th century began the use of Latin/Greek names per species
Dichotomous Key
Used to identify organisms
1) using series of paired statements, which will describe alternative possible characteristics of an organism
2) paired statements which usually describe presence or absence of certain visible characteristics/structures
3) entire processes leads into subsets until you achieve the desired outcome

5. Ex. Of Dichotomous Key

6. BINOMIAL NOMENCLATURE
Carolus Linnaeus developed the binomial nomenclature – a two-word naming system
Each species is assigned a two-part scientific name
1) scientific names are written in italic
2) 1 word = C ; 2 word = c
3) the first part is the genus and the second is the species
Genus – a group of similar species
Species – description of an important trait / an organism’s habitat

7. BINOMIAL NOMENCLATURE
RED MAPLE
SCIENTIFIC NAME = Acer rubrum
GENUS Acer = CONSIST OF ALL MAPLE TREES
SPECIES rubrum = RED MAPLE COLOR

8. CLASSIFYING SPECIES INTO LARGER GROUPS
 try to organize/classify living and fossil species into larger groups that will have a biological meaning
Systematics – science of naming and grouping organisms
These groups are referred to as – taxa
Ex. Professor
Science Professor

9. THE LINNAEAN CLASSIFICATION SYSTEM
Linnaeus developed a classification system that organized species into taxa that formed a hierarchy/set of ordered ranks
Seven hierarchical taxa: Species, Genus, Family, Order, Class, Phylum, and Kingdom
He grouped species according to anatomical similarities and differences
Family – where several genera that share many similarities are grouped into a larger category
Order – closely related families are grouped into the next larger rank
Class – similar orders are grouped
Phylum – classes are grouped; includes organisms that are different but share important characteristics
Kingdom – largest and most inclusive rank
(K)ing (P)hilip (C)ame (O)ver (F)or (G)ravy (S)oup

10. PROBLEMS WITH TRADITIONAL CLASSIFICATION
In a sense, members of a species determine which organisms belong to that species by deciding with whom they mate and produce fertile offspring, which mean there is a “natural” definition of species
Researchers define Linnaean ranks above the level of species b/c over time systematics have emphasized a variety of characteristics and some of these groups have been defined in different ways at different levels
Ex. Linnaean’s classification of organisms according to visible similarities and differences
Modern systematics apply Darwin’s ideas to classification and also try to look beyond simple similarities and differences so thy can ask questions about evolutionary relationships

11. 18.2 Modern evolutionary classification
Key Questions
What is the goal of evolutionary
classification?
What is a cladogram?
How are DNA sequences used in classification?
18.2 Modern evolutionary classification

12. EVOLUTIONARY CLASSIFICATION
The concept of descent with modification led to the study of phylogeny – the evolutionary history of lineages
Advances in phylogeny led to phylogenetic systematics
Goal is to group species into larger categories that reflect lines of evolutionary descent, rather than overall similarities and differences

13. COMMON ANCESTORS
Phylogenetic systematics places organisms into higher taxa whose members are more closely related to one another
The larger the taxon is, the further back in time all of its members shared a common ancestor

14. CLADES
Classifying organisms according to these rules places them into groups called clades – group of species that includes a single common ancestor and all descendants of that ancestor which include living and extinct
How are clades different from Linnaean taxa?
Clade must be a monophyletic group – includes a single common ancestor and its descendants
Some groups of organisms before the arrival are monophyletic
Some are paraphyletic – the group includes a common ancestor but excludes one or more groups of descendants, which means those excluded groups are invalid under evolutionary classification

15. Ex. Of Mono/Paraphyletic taxon

16. CLADOGRAMS
Modern evolutionary classification use a method called cladistics analysis, which compares carefully selected traits to determine the order in which groups of organisms branched off from their common ancestors
Cladogram – links groups of organisms by showing how evolutionary lines, or lineages, branched off from common ancestors
How do you build a cladogram?
1) the diagram shows a single ancestral lineages splitting into two
The point splitting is the node – represents the last point which the two new linages shared a common ancestor
2) the bottom, or root – the common ancestor shared by all the organisms
3) a cladogram’s branching patterns indicate the degree of relatedness among organisms

17. Different Types of Cladograms

18. Ex. of Cladogram

19. Ex. of Cladogram

20. DERIVED CHARACTERISTICS
In contrast to Linnaean taxonomy, cladistic analysis focuses on certain kinds of characters, or derived characteristics when assigning organisms into clades
Derived characteristics – a trait that arose in the most recent common ancestor of a particular lineage and was passed along to its descendants

21. LOSING TRAITS
Ex. Clade Tetrapoda have a derived character of four limbs
Snakes are part of this clade but are not four limbed
How does this work?
The ancestors of the snakes did have four limbs, but somewhere in the lineage that lead to our modern snake, the trait was lost
Because distantly related groups of organisms can sometimes lose the same character, systematics are very cautious about using the absence of a trait as a character in their analysis
You may ask what about whales since they are also not four limbed, but we can clearly tell snakes are more closely related to other reptiles than whales!

22. INTERPRETING CLADOGRAMS
1) the lowest node represents the last common ancestor
2) the forks in the cladogram show the order in which various groups branched off
3) the positions of various characteristics in the cladogram reflect the order in which those characteristics arose in the lineage
4) each derived character listed along the main truck of the cladogram defines a clade
5) derived characters that occur “lower” on the cladogram than the branch point for the clade are not derived for that particular clade

23. Ex. of Cladogram

24. DNA IN CLASSIFICATION: GENES AS DERIVED CHARACTERS
Since all genes mutate over time, shared genes contain differences that can be treated as derived characters
Similarities and differences in DNA con be used to develop hypotheses about evolutionary relationships
In general, the more derived genetic characters two species share, the more recently they shared a common ancestor and the more closely they are related in evolutionary terms

25. NEW TECHNIQUES SUGGEST NEW TREES
The use of DNA characters in cladistic analysis has helped to make evolutionary trees more accurate
Ex. The hooded vulture from Africa, the American vulture, and Storks
Both the hooded and American vultures are in the falcon clade
But American vultures do something odd when they overheat
They urinate on their legs, as they rely on the evaporation to cool them down
Storks also do this, which has led Biologists to try and piece this puzzle together
Molecular analysis shows that the DNA from the American vulture is more similar to storks than African vultures
Suggests that American vultures and storks share a more recent common ancestor than American and African vultures
Molecular analysis is a powerful tool that is now routinely used by taxonomists to supplement data from anatomy

26. 18.3 Building the tree of life
Key Questions
What are the six kingdoms of life as they are now identified?
What does the tree of life show?
18.3 Building the tree of life

27. CHANGING IDEAS ABOUT KINGDOMS
Biologists learned that the two kingdoms – Animalia and Plantae – did not reflect the full diversity of life
Five Kingdoms
Researchers began to study microorganisms which led to the discovery that single-celled organisms were significantly different from plants and animals
They then placed all microorganisms into the kingdom Protista
Next, they placed yeast and molds + mushrooms into the kingdom Fungi
Scientists realized that bacteria lack nuclei, mitochondria, and chloroplasts that were found in other forms of life = prokaryotes (bacteria) placed in Monera

28. CHANGING IDEAS ABOUT KINGDOMS
Six Kingdoms
In the 1990’s, researchers realized that the organisms in Kingdom Monera were actually two genetically and biochemically different groups
This led to separating Monera into Eubacteria and Archaebacteria
Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia
Three Domains
Domain – a larger, more inclusive category than a kingdom
3 Domains are: Domain Bacteria, which corresponds to kingdom Eubacteria, Domain Archaea, which corresponds with kingdom Archaebacteria, and Domain Eukarya, which corresponds with kingdoms Fungi, Plantae, Animalia, and “Protista”
There are quotations around Protista b/c it’s a paraphyletic group and there is no way to put all unicellular eukaryotes into a clade that contains a single common ancestor, all of its descendants, and only those descendants

30. THE TREE OF LIFE
Modern evolutionary classification is a rapidly changing science with the difficult goal of presenting all life on a single evolutionary tree
Biologists regularly change not only the way organisms are grouped, but also sometimes the names of groups
Different from cladograms b/c they are visual presentations of hypotheses about relationships, and not hard fact
Shows current hypotheses regarding evolutionary relationships among the taxa within the three domains of life
Domain Bacteria
Bacteria – unicellular and prokaryotic
Cells have thick, rigid walls that surround a cell membrane
Cell walls contain a substance known as peptidoglycan
They are ecologically diverse, ranging from free-living soil organisms to deadly parasites
Some photosynthesize, while others don’t and some need oxygen to survive while, others are killed by oxygen

31. THE TREE OF LIFE Domain Archaea Archaea – unicellular prokaryotes
Their cell walls do not contain peptidoglycan
Live in extreme environments such as: volcanic hot springs, brine pools, and black organic mud that is totally lacking oxygen
Some of them can only survive in the absence of oxygen
Cell membranes contain unusual lipids not found in any other organisms
Domain Eukarya
Eukarya – all organisms that have a nucleus
“Protists” – Unicellular Eukaryotes
Some people still use the name “protists” for these organisms, but scientists have known for years that they do not have a valid clade

32. THE TREE OF LIFE Domain Eukarya Fungi Plantae Animalia
Heterotrophs with cell walls containing chitin
Most feed on dead or decaying organic matter
Fungi secrete digestive enzymes into their food source to absorb the small molecules into their bodies
Plantae
Autotrophs with cell walls that contain cellulose
Can carry out photosynthesis
Cannot move from place to place
Animalia
Multicellular and heterotrophic
Animal cells do not have cell walls
Most can move

34. CREDITS Miller & Levine Biology ( ©2010)