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Classification and Introduction to
Diversity of Life
This mini unit will be an introduction to diversity.
The following concepts will be covered:
•! Taxonomy
•! Binomial nomenclature
•! Carl Linnaeus
•! Dichotomous key
•! Cladistics- Cladograms
•! Molecular Evidence
•! Three Domains of Life
In the next three units will go through all the kingdoms.
Assessment in this unit will include:
•! Practice Cladogram
Interpretation
•! Practice Dichotomous Key
Interpretation
•! Kingdom Media In-class
How do we distinguish between two animals?
Carl Linnaeus developed the scientific naming system that is still used today.
Organisms can be classified based on physical similarities.
•! Scientific names help scientists to communicate.
•! Some species have very similar common names.
•! Some species have many common names.
Taxonomy is the science of naming and classifying organisms.
A taxon is a group of organisms in a classification system.
Kingdom, Phylum, Class, Order, Family, Genus, Species
Binomial nomenclature is a two-part scientific naming system.
•! uses Latin words
•! scientific names always written in italics
•! two parts are the genus name and species descriptor
A genus includes one or more physically similar species.
•! Species in the same genus are thought to be closely related.
•! Genus name is always capitalized.
•! A species descriptor is the second part of a scientific name.
•! always lowercase
•! always follows genus name; never written alone
Linnaeus’ classification system has seven levels.
•! Each level is included in the level above it.
•! Levels get increasingly specific from kingdom to species.
Limitations
•! Linnaeus taxonomy doesn’t account for molecular evidence (DNA, proteins, etc.)
•! The technology didn’t exist during Linneaus’ time.
•! Linnaean system based only on physical similarities.
Physical similarities are not always the result of close relationships.
Genetic similarities more accurately show evolutionary relationships.
Dichotomous Key
•! A dichotomous key is a method and guide to help identify between species of organisms.
•! A dichotomous key is an organized set of couplets of mutually exclusive
characteristics of biological organisms.
•! Begins with general characteristics then leads to couplets.
Bean Identification
1a.
1b.
Bean round
Bean elliptical or oblong
Garbanzo bean
Go to 2
2a.
2b.
3a.
3b.
4a.
4b.
Bean white
Bean has dark pigments
Bean evenly pigmented
Bean pigmentation mottled
Bean black
Bean reddish-brown
White northern
Go to 3
Go to 4
Pinto bean
Black bean
Kidney bean
Practice:
Use the dichotomous key to identify the grain/bean.
Practice:
You will be given 5 species of fruits. You are to create a dichotomous key using your basic
understanding of the fruits shown. Do this in groups of three on loose-leaf. I would keep an
individual copy because you will be doing an in class assignment making dichotomous keys.
Once you have finished making the key, write all your names, we will mark it together as a
group. Then handed in your marked copy to me.
Rough copy of Dichotomous Key with fruits:
Modern classification is based on evolutionary relationships.
Cladistics is a common method to make evolutionary
trees.
•! classification based on common ancestry
•! species placed in order that they descended from
common ancestor
•! A cladogram is an evolutionary tree made using
cladistics.
•! A clade is a group of species that shares a
common ancestor.
•! Each species in a clade shares some traits with the ancestor.
•! Each species in a clade has traits that have changed.
•! Derived characters are traits shared in different degrees by clade members.
•! More closely related species share more derived characters
•! Represented on cladogram as hash marks
•! Nodes represent the most recent common ancestor of a clade.
•! Clades can be identified by snipping a branch under a node.
Practice Problems
1.! What trait separates Lampreys from tuna this cladogram?
______________________
2.! What separates a
salamander from a turtle?
______________
_______________
3.! Which organism is most
related to the leopard?
____________________
4.! What 4 traits do these two
organisms share?
_____________________
_____________________
_______________________
___________________
5.! Which organism will have
DNA most similar to the
turtle? ______________________________________________
6.! Which organism’s DNA will differ the most from the leopard?
_____________________________________________
Use the cladogram below to answer the questions on the backside of this
worksheet
1.! What 5 traits do these two
organisms share?
____________________
_______ ______________
____________
2.! What trait separates
amphibians from primates
on this cladogram?
________________
___________________
3.! What separates rabbits and
primates from crocodiles
on this cladogram?_______________________________
4.! Which organism is most related to the bird on this
cladogram?_______________________________________
5.! Which organism will have DNA most similar to the bird?
______________________________________________
Molecular evidence: reveals species’ relatedness.
•! Molecular data may confirm classification based on physical similarities.
•! Molecular data may lead scientists to propose a new classification.
Molecular data can include:
•! Proteins
•! Mitochondrial DNA
•! Ribosomal RNA
•! Nuclear DNA
Domains are above the kingdom level.
•! Proposed by Carl Woese based on rRNA studies of prokaryotes.
•! Domain model more clearly shows prokaryotic diversity
•! The tree of life shows our most current understanding.
•! New discoveries can lead to changes in classification.
The Tree of Life has Three Domains
Domain Bacteria includes prokaryotes in the kingdom Bacteria.
•! one of largest groups on Earth
•! classified by shape, need for
oxygen, and diseases caused
Domain Archaea includes prokaryotes in the
•! cell walls chemically different from
bacteria
•! differences discovered by studying RNA
•! known for living in extreme
environments
Domain Eukarya includes all eukaryotes.
•! kingdom Protista
•! kingdom Plantae
•! kingdom Fungi
•! kingdom Animalia
Bacteria and Archaea can be difficult to classify.
•! transfer genes among themselves outside of reproduction
•! blurs the line
between “species”
•! more research
needed to
understand
prokaryotes