Download Taxonomy Taxonomy: field of biology that identifies and classifies

Taxonomy
Taxonomy: field of biology that identifies
organisms
and
classifies
Why do we need it?
 problems with different

common names
languages
can be confusing
examples: woodchuck, groundhog
crayfish, crawdad, rock lobster
fish, starfish, jellyfish
Linnaeus: 18th century
 came up with a system that gave every organism a 2 word name
 called the system binomial nomenclature
There are seven groupings (called taxons) in the Linnean system.
1. Kingdom
2. Phylum
An organism’s name
3. Class
consists of the genus
4. Order
and the species. Genus is
5. Family
first and is capitalized. Both
6. Genus
are underlined or italicized.
7. Species
Recently, a change has been made to taxonomy. Instead of the
kingdom being the largest taxon, taxonomists use domains , which
are located above or before kingdoms on the previous list. There are
3 different domains:
1. Eukarya – includes all organisms that are eukaryotic
2. Prokarya – includes modern bacteria (Eubacteria)
3. Archaea – includes ancient bacteria (Archaebacteria)
that live in very harsh and extreme conditions
Examples of scientific names:
Common Name
Genus
Species
Lion
Felis
leo
Tiger
Felis
tigris
Housecat
Felis
sylvestris
Human
Homo
sapiens
We use Latin
for the names. It is a “dead” language and will not
change in meaning.
Modern taxonomy uses several areas to classify organisms, such as:
1. structural
similarities
2. genetic
similarities
3. biochemical similarities
4. cellular structures
There are 5 kingdoms used in taxonomy (although that number can
vary).
1.
Monera
: includes all bacteria
 unicellular prokaryotes
 most are heterotrophs, some are autotrophs
Please note: with the changes in taxonomy using domains, the Monera
kingdom is now represented by 2 different kingdoms – Eubacteria
and Archaebacteria .
2.
Protista
:
 unicellular and multicellular eukaryotes
 most cells of multicellular protists aren’t specialized
 some are autotrophs , some are heterotrophs
3.
Fungi :
 eukaryotes, most are multicellular
 have cell walls
 heterotrophs
 include molds, mildews, mushrooms, yeasts
4.
Plantae :
 multicellular, eukaryotes
 cell walls
 specialized cells  tissues
 most are autotrophs
5.
 organs
Animalia :
 multicellular, eukaryotic
 heterotrophs
 do NOT have cell walls
 most can move from place to place at some point in their
life cycle
 specialized cells  tissues  organs
Viruses
Virus: an infectious agent made up of a core of nucleic acid and a
protein coat
 Viruses are NOT cells !!!
 do not have a n nucleus , m membrane , or organelles
 do not eat, respire, respond to environment
Viruses are incredibly tiny. For example, 3000 polio viruses could line
up across a typed period from your text.
All viruses have at least 2 parts:
1. core of nucleic acid (some have DNA, some have RNA)
2. capsid: protective protein coat around the core
In viruses that infect animal cells, there is another protective coating
outside of the capsid called an envelope. It’s made of lipid, proteins,
and carbohydrates.
Replication in Viruses
Viruses do not reproduce (which involves cell division); they replicate.
 can’t replicate on their own; have to have a host which is: an
organism that shelters and nourishes something (in this case, a virus)
Living cells act as hosts for viruses and provide all the materials that
viruses need to copy themselves. When a virus enters a cell, it can
immediately replicate or remain relatively inactive.
Lytic Cycle: replication process that rapidly kills a host cell
1. virus invades a host cell and injects its DNA into it
2. viral DNA commands the host cell to make new viruses
3. cell splits apart and releases lots of new viruses
4. new viruses invade other host cells
Lysogenic Cycle: virus does not immediately kill the host cell
1. viral DNA invades the host cell and becomes part of the
host cell’s chromosome
2. the host cell may divide many times and every time, the
viral DNA is replicated with the host’s DNA
3. some viruses stay in the lysogenic cycle for a very long
time; usually, some type of environmental stimulus
eventually causes the viral DNA to separate from the host
DNA
4. the viral DNA then enters the lytic cycle
Classifying Viruses
Because viruses are so diverse, classifying them can be difficult.
There are several different ways of classifying viruses.
1. Shape – filovirus, polyhedral, binal, helical
2. Host – Since most viruses invade only a specific type of
organism, you can classify them according to the host
infected (ex. animal, plant, bacterial).
3. Function – how a virus functions in the host
Viruses in the Biosphere
1. Diseases:
 Many diseases are caused by viruses (colds, polio, measles,
mumps, chicken pox, flu)
 viral diseases can NOT be cured by antibiotics (only good
against bacterial cells)
2. Human Uses:
 vaccines: inject a harmless (weak or dead) form of a virus to
get the immune system to produce cells and proteins that will
kill that type of virus if it enters the body
 genetic engineering: viruses can be used to correct some
genetic defects
 agriculture: control pests without chemical pesticides; create
different color combinations in certain flowers (tulips)