Title: Classification Systems
1Classification Systems
- In general, classification is a method for
organizing information. We tend to classify
things spontaneously. As an example after seeing
enough examples of tables, we form a
classification in which any given object is
either a table or a non-table. Given a new object
we do remarkably well at deciding whether it is a
table. Although there is little scientific value
in this particular classification, it illustrates
their omnipresence.
2- ARISTOTLE (384-322 BC) is often called the father
of biological classification. His classification
scheme referred to common groups, such as birds,
fishes, whales, and bats, and he recognized the
need for groups and group names in the study of
the animal kingdom. But his system was based on
the knowledge that was available in his day.Â
John RAY (1627-1705) used anatomical differences
as the prime rule for classification, bringing
out both the alikeness and differences between
groups--for example, lungs or gills. This is
still a preferred method for identification of
organisms.
3Classifications Group Similar Things Together
- In general, classifications similar things are
grouped together. This definition is by
definition vague there are many reasonable ways
of defining similarity, and hence many different
classifications for the same things. In the
example of tables, we considered the relationship
(similarity) of objects to an abstract definition
of table. This definition was based on a
potential function of the object. In choosing to
classify by "tableness", we assign less
importance to other properties - color, hardness,
age, etc. - that can vary without altering the
utility of the object as a table.
4- The intended use of a classification is an
integral part of deciding what properties it
should be based upon. Here are some other
classifications that you have encountered the
books in a library - often the library will use a
dewey decimal system to make it easy to find
specific books and titles. A visit to a large
library will clearly demonstrate a need for such
a system and a hardware store (organized by
purpose of use - painting, hardware, lumber,
seasonal, etc...).
5Classifications are often arranged in a Hierarchy
- A key property of classifications is that they
can be nested within one another, creating an
hierarchy. Thus, any group within a
classification can be split in still greater
detail. For example, objects that have been
classified as Tables might be subdivided into
Kitchen tables, Picnic Tables, Desks, etc.
Similarly, listings in a telephone directory are
first classified by the Community, and then
within each of these categories they are further
classified alphabetically.
6- There is no limit to the depth of a hierarchical
classification. Most only have a few levels, but
there are some that go quite far. When
alphabetical order is considered carefully, it is
seen that the first level of classification deals
only with the first letter of each word. Then all
words starting with the same first letter (for
example "c") are categorized by their second
letter, adding a second level to the alphabetical
classification. This process continues one letter
at a time until all words have been
distinguished.
7Why Do We Classify Organisms?
- Biologists group organisms to represent
similarities and proposed relationships. - Classification systems change with expanding
knowledge about new and well-known organisms.
Tacitus bellus
8Classification and Phylogeny
- Binomial Nomenclature
- Hierarchical Classification
- Systematics Evolutionary Classification
Populus tremuloides Quaking Aspen
9Binomial Nomenclature
- Carolus von Linnaeus
- Two-word naming system
- Genus
- Noun, Capitalized, Underlined or Italicized
- Species
- Descriptive, Lower Case, Underlined or Italicized
Carolus von Linnaeus(1707-1778) Swedish
scientist who laid foundation for modern taxonomy
10Biological Classification and the Linnaean
System.
- Linnaeus defined the biological classification
system that we still use for plants and animals,
and, with relatively minor modifications, for
fungi and microorganisms. It is a hierarchical
system that starts with a few categories at the
highest level, and further subdivides them at
each lower level. - In the Linnaean system, to uniquely name a
species it is necessary to supply both the genus
and species. In the case of animals, Linnaean
classifications often reflect our natural sense
of similarity.
11- Think about a Polar Bear. Develop a mental image
of it. How would you describe it to someone who
has never seen one? Take a moment to consider
carefully . . .
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13- Very likely your mental image was a visual one
like the picture. Humans primarily emphasize
traits that we can see as our primary source of
information is our sense of sight. However, there
is no reason that a polar bearor any other
organism could not be described in terms of
touch, smell, and/or sound as well. Think about
an polar bear again but this time in terms of
non-visual traits . . .
14- Not surprisingly, biologists also classify
organisms into different categories mostly by
judging degrees of apparent similarity and
difference that they can see. The assumption is
that the greater the degree of similarity, the
closer they are related in a biological sense.
15- On discovering an unknown organism, researchers
begin their classification by looking for
features that seem to have the same function as
those found on other species. Next it will have
to be determed whether or not the similarities
are due to an independent evolutionary
development or to a common ancestor. If the
latter is the explanation, then the two species
are probably closely related and should be
classified into the same or near biological
categories. - Homologies are physical features, of different
organisms, that have a similar appearance or
function because they were inherited from a
common ancestor that also had them. For instance,
the forelimb of a bear, the wing of a bird, and
your arm have the same functional types of bones
as did our shared reptilian ancestor--these are
homologous structures. The more homologies two
organisms possess, the more likely it is that
they have a close genetic relationship.
16- Listing characteristics that distinguish one
species from another has the effect of making it
appear that the species and their distinctive
attributes are fixed and eternal. We must always
keep in mind that they were brought about by
evolutionary processes that operated not only at
some time in the past, but which also continue to
operate today and will undoubtedly give rise to
new forms in the future.
17- We also need to realize that most species are
genetically diverse. When you think of an animal,
such as the moose shown below, and describe it in
terms of its specific traits (fur color patterns,
Antler shape, etc.), it is natural to generalize
and to think of all Moose that way. To do so,
however, is to ignore the reality of variation in
nature.
18Linnaean Nomenclature
- The standard nomenclature for species is
attributed to Carolus LINNAEUS (1707-1778). He
applied it consistently to plants in Species
Plantarum (1753), and to animals in Systema
Naturae (10th ed., 1757). Linnaeus' system was
readily applicable to the new concept of
evolution of Charles DARWIN, which was published
in On the Origin of Species (1859). - Darwin put forth the theory that organisms evolve
by the process of natural selection. The theory
had no immediate effect on existing
classifications themselves, but it provided a new
explanation and foundation for the classification
schemes being used. The closer together
organisms were classified, the closer in
evolutionary history they would be linked. This
approach is key to modern classification schemes.
19- The Linnaean method for classification of living
things groups organisms together based on
presumed similarites in structures (Homologies).
The assumption is that the more homologies the
organisms in question share, the closer they must
be in terms of evolutionary distance. The larger,
more inclusive divisions of the Linnaean system
(beyond species) are created by including
together closely related groups of the
immediately lower divisions. The result is a
pyrimidal system of classification with the
highest category consisting of all living things.
The lowest category consists of a single species.
Each of the categories above species can have
numerous subcategories.
20- Linnaeus arranged classification categories as a
series of nested groups. His sequence from
broadest to smallest category is Kingdom,
Phylum, Class, Order, Family, Genus, and Species.
To remember this order you need only to remember
the following - King (Kingdom) Philip (Phylum) Came (Class) Over
(Order) For (Family) Good (Genus) Soup (Species)
21- Related groups of organisms were determined by
the many shared characteristics especially those
having to do with maintenance, feeding, and
digestion. - The basic unit in the Linnaean classification of
living forms is the species (plural, species).
Each species is given a unique, two part Latin
name the name is always underlined or italicized
in print. The name consists of the genus, which
is a group of species more closely related to one
another than to any other group, followed by the
specific name, which identifies a particular
species within a genus. The first letter of the
genus is capitalized, while the specific name is
in lowercase, as in Felis domesticus (House Cat)
and Salmo salar(Atlantic Salmon). The binomial
species name replaced the much longer
descriptions of earlier classifications.
22- Linnaeus named groups of organisms for the
defining characters that he noticed. For example,
the name Mammalia to the group of animals that
possess mammary glands and secrete milk to
nourish their young. He also recognized that
monkeys are most nearly like humans, and as a
logical consequence of strictly biological
classification, humans would be grouped not only
in the class Mammalia but in the same
representative division with the monkeys and
apes.
23Hierarchical Classification
- Taxonomic categories
- Kingdom King
- Phylum Philip
- Class Came
- Order Over
- Family For
- Genus Green
- Species Soup
24Kingdoms and Domains
The three-domain system
Bacteria
Archaea
Eukarya
The six-kingdom system
Bacteria
Archaea
Protista
Plantae
Fungi
Animalia
The traditional five-kingdom system
Monera
Protista
Plantae
Fungi
Animalia
25SystematicsEvolutionary Classification of
Organisms
- Systematics is the study of the evolution of
biological diversity, and combines data from the
following areas. - Fossil record
- Comparative homologies
- Cladistics
- Comparative sequencing of DNA/RNA among organisms
- Molecular clocks
26Taxonomic Diagrams
Mammals
Turtles
Lizards and Snakes
Crocodiles
Birds
Mammals
Turtles
Lizards and Snakes
Crocodiles
Birds
Cladogram
PhylogeneticTree
27Dichotomous Keys Identify Organisms
- Dichotomous keys versus evolutionary
classification - Dichotomous keys contain pairs of contrasting
descriptions. - After each description, the key directs the user
to another pair of descriptions or identifies the
organism. - Example 1. a) Is the leaf simple? Go to 2 b)
Is the leaf compound? Go to 3 - 2. a) Are margins of the leaf jagged? Go to
4 b) Are margins of the leaf smooth? Go to 5
28Biological Classification
- Biological classification is the arrangement of
organisms into categories that express their
PHYLOGENY, or line of descent, based on
information such as structure, development,
biochemical functions, and evolutionary history
of organisms. The purpose of such a
classification is to provide a clear and
practical way to organize and communicate
information about organisms. Classification can
show relationships between different ancient and
modern groups, indicate the evolutionary pathways
along which present-day organisms may have
developed, and provide a basis for comparing
experimental data about different plant and
animal groups. Organisms included in a group
share a common genetic heritage in their genetic
material, and they must be more closely related
to each other than they are to the members of
other groups of the same rank. However,
classifications of organisms are modified as new
information comes forward and as a result the
phylogeny would change.
29- Taxonomy is the theory and practice of
classifying organisms. The first scheme for
classifying animals into logical groupings may
have been proposed by Aristotle more than 2,000
years ago. Since that time, many new systems have
been proposed none, however, has succeeded in
fitting all plants, animals, and microorganisms
into a single, completely satisfactory scheme.
For example, some taxonomists classify algae with
the protista or consider them plants. Recently,
biotechnological techniques have enabled
researchers to compare the DNA of various
organisms to decipher the phylogeny of some
organisms and helped to distinguish some closely
related species with similar appearance.
30- Assigned activities
- Read the Following Pages from McGraw Hill Ryerson
- 108 - 109
- Complete the Mini Lab on Page 109 - Organizing
Life - Complete the Laboratory Exercise on Page 110 -
111 Creating a Dichotomous Key
31Taxonomy
- What does this word mean?
32Definition of taxonomy
- It is the science of classification
- It deals with organizing
- Similar to the way in which you might organize
your desk at home
33Desk
- Top drawer might have all your writing utensils,
sharpeners, erasers, etc. - The top side drawer might have all of your paper
in it and perhaps some envelopes - The next drawer down might have some drawing
tools, e.g. compass, ruler, protractor - What have you really done in organizing your desk
this way?
34Organizing
- There are many ways to organize a room, a desk, a
closet - In the desk above, we put things together that
were similar in there usage - In a closet, you might organize clothes according
to color or type of article - Can you think of any other ways to organize
different types of things?
35Usefulness
- Helps when dealing with large numbers of
organisms - Will allow you to find something easier
- Might help someone who is unfamiliar with the
items learn them easier
36Systems
37Aristotle
- Simple
- Used 2 kingdoms
- Plant
- Animal
38Plants according to Aristotle
39Animals according to Aristotle
- Land-dwelling
- Air-dwelling
- Water-dwelling
40Problems
- Do you see any problems with this type of system?
41Carolus Linnaeus
- Sometimes called the Father of Modern Taxonomy
- His basis for classification was structure
42Scheme
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
43Memorizing Help
- King Phillip Came Over For General Science
- Each group gets smaller and smaller in the
numbers of organisms it contains - Within each group, the organisms get more similar
as you go from Kingdom to Species
44Scientific Names (Binomial Nomenclature)
- The scientific name of an organism is composed of
the Genus and Species names of that organism
45Lets Look at Man
- Kingdom - Animalia
- Phylum - Chordata
- Class - Mammalia
- Order - Primate
- Family - Hominidae
- Genus - Homo
- Species - Sapiens
46Man (contd)
- We are in the kingdom Animalia with all the other
animals of the World - We are in this species Sapiens only with
ourselves - Our scientific name is
- Homo sapiens
- This is the only correct way to write this name
47Species
- Two organisms are members of the same species if
they can mate and produce fertile offspring - Two organisms can have the same species names and
not be in the same species - Scientific names are reversed of ours
- Your last name is a family name usually based on
your fathers last name - Your first name is a given name that your parents
pick for you
48Species (contd)
- If you discover a new organism, you are given the
right to name that organism - It will be in a given genus based on structure
and other criteria (modern system) - You assign a species name (maybe yours the state
or country where discovered a prominent color,
etc.)
49Modern System of Taxonomy
- Based mostly on evolution
- What organisms have evolved from what other
organisms
50Kingdoms in Modern System
- Monera
- Protista
- Fungi
- Plantae
- Animalia