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Chapter
18
Classification
18 – 1 Finding Order in Diversity
Evolution has lead to a staggering variety or organisms Biologists have identified and named about __________________________ species
so far They estimate anywhere between 2 and 100 million additional species have yet to be
discovered
Why Classify?
To study the diversity of life, biologists use a classification system to name organsisms and group them in a logical manner
Taxonomy - _____________________________________________________________
Assigning Scientific Names
By the 18th century, European scientists recognized that referring to organisms by common names was confusing
Common names vary among regions within a country
Ex.)
Scientists use Latin and Greek for scientific names
Early Efforts at Naming Organisms
First attempts at standard scientific names often described physical characteristics As a result, these names could be 20 words long!Ex.) The English translation of the scientific name of a particular tree might be “Oak with deeply divided leaves that have no hairs on their undersides and no teeth around their edges.”
Binomial Nomenclature
Carolus Linnaeus (18th Century) Swedish Botanist Developed a system for naming organisms
Binomial Nomenclature - ___________________________________________________
Rules for Binomial Nomenclature
1.
2.
3.
Ex.) Genus species or Genus species or G. species
The name often tells you something about the speciesEx.) Tyranosaurus Rex
Linnaeus’s System of Classification
Taxon (taxonomic category) - _______________________________________________________________________________________________________________________
Linnaeus’s system of classification uses seven taxonomic categories
Mnemonic Device
K______________________
P______________________
C______________________
O______________________
F______________________
G______________________
K _______________________
P________________________
C________________________
O________________________
F________________________
G________________________
s ________________________
s_______________________
Name _________________________________ Date _____________________ Per ____
18 -1 Section Review
1. How are living things organized for study?
2. Describe the system for naming species that Linnaeus developed.
3. What are the seven taxonomic categories of Linnaeus’s classification system?
4. Why do scientists avoid using common names when discussing organisms?
5. Which category has more biological meaning—all brown birds or all hawklike birds? Why?
18 -2 Modern Evolutionary Classification
Back in Linneaus’s time when classifying organisms he compared structures and details of anatomy
Problems with Traditional Classification
Sometimes, due to convergent Evolution organisms that are quite different from each other evolve similar body structures
Ex.)
Evolutionary Classification
Darwin’s theory of evolution changed the entire way that biologists thought about classification
Biologists now group organisms into categories that represent ______________________________________________________, not just physical similarities
Classification Using Cladograms
Many biologists now prefer a method called _________________________________ This method of classification identifies and considers only those characteristics that
arise as lineages evolve over time
Derived characteristics - _________________________________________________________________________________________________________________________________________________________________________________________________
Cladogram - _____________________________________________________________________________________________________________________________________________________________________________________________________________
Similarities in DNA and RNA
Suppose you were trying to compare diverse organisms such as yeast and humans It wouldn’t make sense to try to classify anatomical similarities The genes of many organisms show important similarities at the molecular level These similarities can be used as criteria to help determine classificationEx.) Myosin in humans & yeast
Molecular Clocks
Comparison of DNA can also be used to mark the passage of evolutionary time
Molecular clock - _________________________________________________________________________________________________________________________________________________________________________________________________________
Mutations happen all the time at about the same rate A comparison of DNA sequences in two species can reveal how dissimilar the genes
are The degree of dissimilarity is an indication of how long ago the two species shared a
common ancestor
Name _________________________________ Date _____________________ Per ____
18 -2 Section Review
1. How is information about evolutionary relationships useful in classification?
2. How are genes used to help scientists classify organisms?
3. What is the principle behind cladistic analysis?
4. Describe the relationship between evolutionary time and the similarity of genes in two species.
5. have new discoveries in molecular biology affected the way in which we classify organisms compared with the system used by Linnaeus?
18 -3 Kingdoms and Domains
In taxonomy, as in all areas of science, ideas and models change as new information arises, some explanations have been discarded altogether, whereas others such as Darwin’s theory of evolution by natural selection, have been upheld
So it should not be surprising that since the 1800’s, the tree of life has been revised and edited since the discovery of all this new information
The Tree of Life Evolves
Before Linnaeus’s time, the only two Kingdoms that existed were _________________________________________________
As scientists discovered new organisms that didn’t fit into the plant or animal category, they made a new category
The Old 5 Kingdom System for Classification
1.
2.
3.
4.
5.
In recent years, as evidence about microorganisms continued to accumulate, biologists come to recognize that the Monera were composed of two distinct groups
The New 6 Kingdom System for Classification
1.
2.
3.
4.
5.
6.
The Three Domain System
Molecular analysis has given rise to a new taxonomic category that is now recognized by many scientists
Domain - _______________________________________________________________
3 Domains
1. o
2.o
3.o
Domain Bacteria
Important Characteristics
Prokaryotic - __________________________________________________________ Some photosynthesize
Some need oxygeno Aerobic - ______________________________________________________
Some don’t need oxygeno Anerobic - _____________________________________________________
Domain Archaea
Important Characteristics
Live in extreme environmentsEx.)
Domain Eukarya
Consists of all organisms that have a ___________________________
Protista
Important Characteristics
eukaryotic - __________________________________________________________ cannot be classified as animals, plants or fungi, but share many characteristics with
plants, animals and fungi
Plant Like Protists
Photosynthetic - _______________________________________________________
Animal Like Protists
heterotrophic - ________________________________________________________
Fungus Like Protists
Fungi
Important Characteristics
Ex.) Mushrooms, Yeast
o heterotrophs feed on ________________________________________________ secrete digestive enzymes into food source then absorb the food into their bodies some are parasites spread and reproduce by _________________________ Many are used in medicine
ooo
Plantae
Important Characteristics
Photosynthetic autotrophs - ______________________________________________________________________________________________________________________
Animalia
Important Characteristics
heterotrophic incredible diversity
Name _________________________________ Date _____________________ Per ____
18 -3 Section Review
1. What are the six kingdoms of life as they are now identified?
2. What are the three domains of life?
3. Why was the kingdom Monera divided into two separate kingdoms?
4. Why might kingdom Protista be thought of as the “odds and ends” kingdom?
5. Which kingdoms include only prokaryotes? Which kingdoms include only heterotrophs?