C LASSIFICATION Why do you think scientists like to put organisms into groups, like mammals or...
-
Upload
pierce-moody -
Category
Documents
-
view
219 -
download
1
Transcript of C LASSIFICATION Why do you think scientists like to put organisms into groups, like mammals or...
CLASSIFICATIONWhy do you think scientists like to put organisms into groups, like mammals or insects?
WHAT IS CLASSIFICATION?
Classification is the arrangement of organisms into orderly groups based on their similaritiesClassification is also known as taxonomy
Taxonomists are scientists that identify & name organisms
Taxonomists classify organisms into groups called taxon
WHY CLASSIFY?
Scientists have classified about 2 million speciesHowever, there are many more
organisms than we have found. Estimates usually range from 3-10
million, but go as high as 50 millionThat shows Earth has a tremendous
amount of biodiversity(variety of organisms)
This is only 1-5% of all organisms that have ever lived!!!!!
Sea “horse”??
WHY CLASSIFY?
Accurately & uniformly names organisms Prevents misnomers such as starfish
& jellyfish that aren't really fish Uses same language (Latin or some
Greek) for all names
EARLY TAXONOMISTS
2000 years ago, Aristotle was the first taxonomistAristotle divided organisms into
plants & animalsHe subdivided them by their habitat
---land, sea, or air dwellers
CAROLUS LINNAEUS: 1707 –1778
18th century taxonomistClassified
organisms by their structure
Developed naming system still used today
CAROLUS LINNAEUS
Called the “Father of Taxonomy”Developed the modern system of naming known as binomial nomenclatureTwo-word naming system
BINOMIAL NOMENCLATURE
Genus speciesLatin or GreekCapitalize
genus, but NOT species
Underline when writing
Italicized in print
American Robin
BINOMIAL NOMENCLATURE
The International Code for Binomial Nomenclature contains the rules for naming organisms
All names must be approved by International Naming Congresses (International Zoological Congress)
This prevents duplicated names Organisms are often named using descriptive
words, like habitat or a physical characteristic OR sometimes using the person whom discovered them
LEVELS OF CLASSIFICATION
The levels of classification are a hierarchy of groups (taxa) from broadest (domain) to most specific (species)
LEVELS OF CLASSIFICATION
Domain Kingdom Phylum Class Order Family Genus Species
Sometimes subspecies is added to the bottom of the list Subspecies
are the same species, but they live in different areas
SYSTEMATICS
Systematics is a science whose goal is to classify organisms in terms of their natural relationships Phylogenetics is a type of
systematics
PHYLOGENETICS
The analysis of the evolutionary or ancestral relationships among taxa.
Classification is based on evolutionary relationshipsFound by studying RNA, DNA,
amino acids, homologous structures, and embryos
These relationships are often shown in a cladogram
CLADISTICS
Cladogram-A diagram showing how organisms are related based on shared, derived characteristics such as feathers, hair, or scalesShared characters are features that ALL
members of a group have in common. For example, all organisms in the Domain Eukarya domain have true nuclei
Derived characters are features that evolved only in the group under consideration. Feathers for example, are believed to have evolved only in the birds, not from a common ancestor that they have with reptiles.
CLADISTICS
Cladograms are organized into clades, which is an ancestor and all of its descendants.
Cladograms are not only based on physical features, they are also based on biomolecular similarities (like DNA, chromosomes and proteins)
Outgroups-have no shared characteristics with the other organisms in the diagram and are only distantly related
CLADOGRAM
Feathers are a derived characteristic in the birds
Hagfish are the outgroup
Jaws are a shared characteristic between all organisms except the hagfish
CLADOGRAM
Hair is a derived characteristic in leopards (on this cladogram, only leopards have hair) NOTE-hair is a shared characteristic in the
previous cladogram, so these characteristics can change based on the cladogram
Character tables may help you make cladograms
DICHOTOMOUS KEYS
Used to identify organisms"Dichotomous" means "divided
into two parts". Characteristics given in pairsRead both characteristics and
either go to another set of characteristics OR identify the organism
DICHOTOMOUS KEYS
Always read both choices, even if the first seems to be the logical one at first.
Be sure you understand the meaning of the terms involved. Do Not Guess.
When measurements are given, use a calibrated scale. Do Not Guess.
Since living things are always somewhat variable, do not base your conclusion on a single observation. Study several specimens to be sure your specimen is typical.
If the choice is not clear, for whatever reason, try both divisions. If you end up with two possible answers, read descriptions of the two choices to help you decide
DICHOTOMOUS KEYS
1. a. Bean round………..Garbanzo bean
b. Bean elliptical or oblong…..Go to 2
2. a. Bean white…………White northern
b. Bean has dark pigments……Go to 3
3. a. Bean solid in color…….Go to 4
b. Bean is spotted……..….Pinto bean
4. a. Bean black…………........Black bean
b. Bean reddish-brown…….Kidney bean
MAKING DICHOTOMOUS KEYS
Eliminate an organism in every step (one part leads to a name, the other part leads to another step)
Use measurements rather than terms like "large" and "small".
Try to make the choice a positive one -something "is" instead of "is not".
MAKING DICHOTOMOUS KEYS - CONTINUED
If possible, start both choices of a pair with the same word.
If possible, start different pairs of choices with different words.
Precede the descriptive terms with the name of the part to which they apply.(like legs are red instead of red legs)