1. Chapter 15: Biological Classification

2. What is this?

3. These are some of the common names for this animal
These are some of the common names for this animal. Scientists have assigned it a single scientific name: Porcellio scaber
Sow bug
Wood louse
Potato bug
Pill bug
Roly-poly

4. The Importance of Scientific Names
Each kind of organism on Earth is assigned a unique two-word scientific name
Binomial nomenclature
All biologists, regardless of their native language, use scientific names when speaking or writing about organisms
Most organisms also have common names
Using scientific names enables scientists to exchange information about an organism and to be certain that they are referring to the same living thing

5. What’s in a Scientific Name?
First word describes the organism in a general way
The second word identifies the exact kind of living thing
The first word of a scientific name is the name of the genus to which the organism belongs
Group of animals that share major characteristics
The second word in a scientific name identifies one particular kind of organism within the genus
Scientists call each different kind of organism a species
The correct name for an organism must include BOTH parts of its scientific name

6. Comparison of Red Oak and Willow Oak
Genus Name
Quercus
Scientific Name
Quercus rubra
Quercus phellos
Traits
Acorns about 25mm long
Common in open Northeastern forests; tolerant of city soot and cold temperatures
Lobed leaves
Acorns about 15mm long
Popular shade tree found in the South; grows well in rich, moist soil
Unlobed, narrow leaves

7. Scientific Names Must Conform to a Set of Rules
All scientific names must consist of Latin words
Two different organisms cannot be assigned the same name
Organisms in different genera cannot have the same genus name
When choosing a name for a species, biologists often pick a name that describes the appearance or distribution of an organism

8. The second word of a scientific name is often descriptive of an organism or its distribution. The green anole lizard Anolis carolinensis and the chickadee Parus carolinensis are both found in North Carolina and South Carolina.

9. Tyrannosaurus rex, which means “tyrant-lizard-king,” was named for its enormous teeth and tremendous size. This dinosaur measured about 50 feet in length.
The frog Rhinoderma darwinii was named to honor Charles Darwin.

10. Why are Scientific Names in Latin?
In the Middle Ages, when scientists began to name organisms, Latin was used in academic circles
Scientists and other scholars found it easier to communicate with each other in Latin
Latin was the language of the scholar and was used for all spoken and written communication
Easier to still use Latin than to rename all 1.4 million known organisms
Latin is a universal language

11. Linnaeus Devised the Two-Name System
The modern system of naming organisms was developed by Swedish botanist Carl Linnaeus
In Linnaeus’s day, organisms were given very long Latin names (sometimes more than 15 words), which were often changed according to the whims of particular scientists
Linnaeus assigned a standard, two-word Latin name to each organism known in his time

12. Writing a Scientific Name is Simple
When you write a scientific name, always capitalize the genus name
Begin the second word with a lowercase letter
Both parts of a scientific name are underlined or written in italics
Homo sapiens
After the first use of the full scientific name, the genus name can be abbreviated as a single letter if the meaning is clear
H. sapiens

13. Classification of Living Things
The Greek philosopher Aristotle grouped animals by their physical similarities
Today biologists classify organisms based on their physical, genetic, biochemical, and behavioral similarities
The classification of organisms is based on decisions made by many scientists using available information

14. Classification of Living Things
The science of classifying living things is called taxonomy
Taxonomists are scientists who examine, classify, and argue about where organisms fit in a group
In a hierarchal system of classification, species are assigned to genera, genera are assigned to families, and families are assigned to groups of increasing size

15. Organisms are Classified by Similarity
In biological classification, organisms are assigned to a group because they share distinctive characteristics with other members of that group
The biological hierarchy of classification has seven different levels
Kingdom, phylum, class, order, family, genus, and species

16. Organisms are Classified by Similarity
The smallest group in biological classification is the species
Similar species are collected into a genus
Similar genera are united into a family
Families that are alike are combined into an order
Similar orders are collected into a class
Classes are united into a phylum
Finally, similar phyla are collected into a kingdom
The more classification categories two species share, the more traits they have in common

17. Kingdom
Phylum
Class
Order
Family
Genus
Species

18. Biological Classification
Kristy
Poured
Coffee On
Fred’s
Green
Shirt
Kingdom
Phylum
Class
Order
Family
Genus
Species

19. Classification and Evolution
The biological hierarchy of classification is based on the fact that different degrees of similarity exist among organisms
For Darwin, classification provided strong evidence supporting evolution
Organisms are similar because they descended from a common ancestor
The more similarities two organisms share, the more recently they shared a common ancestor
Thus, the more classification categories two organisms share, the more closely related they are

20. Similarity Does not Guarantee Close Relationship
Compare the two ocean-dwelling animals seen here
Both have stream-lined bodies, paddle-like fins, and flattened tails
Would you say these organisms are closely related?

21. *belongs to the class Chondrichthyes
*gills obtain oxygen from water
*belongs to the class Chondrichthyes
*skin has placoid (toothlike) scales
*skeleton of cartilage
*vertical tail fin
*breathes air through lungs
*belongs to the class Mammalia
*skin has hair
*skeleton of bone
*horizontal tail fin

22. Similarity Does not Guarantee Close Relationship
Similar appearance does not guarantee common ancestry
Because the number of differences between sharks and dolphins far exceeds the number of similarities, it is easy to reject the hypothesis that these animals are close relatives

23. Methods of Taxonomy
The example of the shark and dolphin illustrates the difficulty in determining which similarities will be useful when classifying an organism
There are two alternative methods of choosing which similarities are important
The first method is cladistics

24. Taxonomy and Technology
Biologists have traditionally compared the appearances of organisms in order to discover the relationships among them
Biologists also consider the behavioral patterns, methods of reproduction, life cycles, and development from fertilization to adulthood
Technological advances have enabled biologists to study the genes that produce the traits used to classify organisms

25. Taxonomy and Technology
Taxonomists use techniques of molecular biology to compare the DNA nucleotide sequences of different organisms
Comparisons of DNA sequences are especially important for the taxonomist because mutations are random events
As time passes, more mutations tend to occur in the DNA of a particular species
Thus, DNA acts as a “molecular clock”

26. What Is a Species?
A species is just a level in the classification system to which scientists assign very similar organisms
Over time, species change and give rise to new species in a process known as speciation
Biologists have traditionally defined a species as organisms that are able to interbreed with each other to produce fertile offspring and that usually do not reproduce with members of other groups

27. What Is a Species? This definition works well for most animals
For example, the horse and the zebra belong to different species
Although they can mate, the resulting offspring, the “zebroid”, is sterile
Reproductive barriers between species are not always perfect
Hybrids are offspring that result from interbreeding by individuals of different species
Coyotes, dogs, and wolves

29. A Species is a Unique Kind of Organism
A species is basically a unique kind of organism
Members of a species share at least one inherited characteristic not found in other similar organisms
In sexually reproducing species, this distinctive characteristic is maintained from generation to generation because members of different species do not interbreed

30. Six – Kingdom System
Biologists used to classify every living thing into either kingdom Plantae or kingdom Animalia
However, numerous living things do not quite fit either description
For example, where would a mushroom fit?
Since Linnaeus’s time, biologists have learned a great deal about the structure and function of living things

31. Six – Kingdom System
This information has enabled them to make increasingly precise distinctions among the major groups of organisms
Most biologists now use a six-kingdom system of classification
Archaebacteria
Eubacteria
Protista
Fungi
Plantae
Animalia

32. Bacteria
All prokaryotes, also called bacteria, are in the kingdoms Archaebacteria or Eubacteria
The bacteria represent the most ancient groups on earth
They have adapted to almost every environment
All bacteria lack cell nuclei

33. Kingdom Archaebacteria
The archaebacteria evolved before oxygen filled our atmosphere and now are found in extreme environments
Fewer than 100 species have been recognized so far
Archaebacteria are believed to be the ancestors of the protists

35. Kingdom Eubacteria
Contains most of the common bacteria that share our world
They are an extremely diverse group, containing both autotrophic and heterotrophic forms
Approximately 5,000 species have been characterized so far, but many more exist
Eubacteria are believed to be the ancestors of mitochondria and chloroplasts, organelles within eukaryotic cells

37. Kingdom Protista
All the multicellular eukaryotes not classified as plants, animals, or fungi are assigned to this kingdom
Protists include protozoa, such as Amoeba and Paramecium, and algae, such as seaweeds and kelps
Slime molds and water molds also belong to this kingdom

39. Kingdom Fungi Mushrooms, yeast, and molds are members of this kingdom
Instead of roots, stems, and leaves, fungi are made of thin filaments that penetrate the soil or decaying organisms, absorbing nutrients from them
Fungi do not contain chloroplasts and cannot make their own food by photosynthesis

41. Kingdom Plantae
This kingdom includes only terrestrial multicellular organisms that use photosynthesis to obtain their nutrients
Nearly all plants occur on dry land, but a few grow submerged in fresh water, and a very few grow at the edges of the sea
Plants cells have cell walls
Because some green algae are so similar to plants they have been identified as the ancestral groups for this kingdom

43. Kingdom Animalia
The first members of this kingdom evolved in the ocean
The largest number of animal phyla are still found only in the sea
Organisms in kingdom Animalia are multicellular
Animals do not photosynthesize
Their cells do not have cell walls
Nearly all animals have some sort of nervous system