Download Chapter 23 - Angelfire

CHAPTER 23
CLASSIFICATION OF ORGANISMS
5/24/2017
CLASSIFICATION
OF ORGANISMS

30 million species are estimated to live
on Earth
 Only 1.5 million have been named

Taxonomy – science of naming
organisms and grouping them into
categories
First developed by Aristotle
Modern method developed by Carolus
Linnaeus (1758)
5/24/2017
CLASSIFICATION

Linnaeus introduced the system of binomial
nomenclature.
 Each organism gets two Latin names (genus and
species)



Species – organisms that can interbreed
Genus - many closely related organisms
Scientific names must be written in italics or must be
underlined:
 genus name is capitalized
 species name is written in lower case
 Homo sapiens or Homo sapiens (humans)
5/24/2017
CLASSIFICATION OF
ORGANISMS

Linnaeus also placed organisms into taxonomic
categories, the largest of which is the kingdom.
 Were originally two kingdoms – animals & plants



Recently a grouping above kingdom, called
domain, was introduced.
Organisms are now placed into 3 domains:
Eubacteria
Archaea
Eucarya
Each domain is subdivided into kingdoms
5/24/2017
CLASSIFICATION OF
ORGANISMS




Domain Eucarya has 4 kingdoms:
 Plantae
 Animalia
 Fungi
 Protista
A kingdom is further subdivided into a phylum
(known as a division in Plantae)
Further subdivisions are class, order, family,
genus, and species
Hierarchy of classification: domain, kingdom,
phylum (division), class, order, family, genus,
and species.
5/24/2017
DOMAINS EUBACTERIA AND
ARCHAEA




Members are commonly known as bacteria
Though similar, the two domains have
significant differences in metabolic
activities.
Some are disease-causing, most are not
Differences between the two are based on
DNA and RNA sequences
5/24/2017
EUBACTERIA

Three common shapes:
spherical
rod
spiral

Classified as prokaryotes, characterized by:
 no nucleus






5/24/2017
single, circular strand of DNA
reproduce by binary fission
move by flagella or slime they produce
some are aerobic and others anaerobic
some are parasites
some are saprophytes (decomposers)
BINARY FISSION IN BACTERIA
5/24/2017
ARCHAEA

Ancient prokaryotic bacteria, but differ from
“regular” bacteria in that:
 Found in extreme environments such as:
hot springs at 113º C (above boiling
point)
high salt
acidic places
 Some have special kinds of chlorophyll
5/24/2017
EUCARYA



Eukaryotic cells are larger than those of
prokaryotes (1000 times more volume)
Cells have membrane-bound organelles
(mitochondria, ER, Golgi, lysosomes, etc.)
Eucarya are divided into:





5/24/2017
Protista
Fungi
Plantae
Animalia
PROTISTA
All are single celled
 Approximately 60,000 different species
 Found in fresh water, marine, and
terrestrial habitats
 Many have chlorophyll and are
autotrophs
 Some reproduce sexually

5/24/2017
FUNGI






Have a rigid, thin cell wall composed of
chitin; over 70,000 species
Do not have chlorophyll; Nonmotile
Include molds and mushrooms; most are
multicellular
Some are single-celled (yeasts)
Function mainly as decomposers
(saprophytes)
Some are parasitic
5/24/2017
PLANTAE





All are nonmotile, terrestrial, multicellular
organisms capable of producing their own food
Have cellulose in their cell walls
300,000 species have been identified and of
these, 85% are flowering plants
Members of this group can be vascular or
nonvascular.
Some are seed producing, some (ferns) lack
seeds
5/24/2017
PLANTAE


Have unique lifecycles:
Haploid gametophyte stage – produces
haploid sex cells by mitosis
Diploid sporophyte stage – produces
haploid spores by meiosis.
Capable of both sexual and asexual
reproduction
5/24/2017
ANIMALIA



All are heterotrophic and multicellular
All are motile (at least during some part
of their life)
All are capable of reproducing sexually,
but some can reproduce asexually
5/24/2017
VIRUSES



Consist of a nucleic acid core surrounded
by a coat of protein (capsid)
Obligate intracellular parasites
Are not members of any domain or
kingdom
Not considered living things
Reproduce only when they are in their host
cell
5/24/2017
VIRUSES


Once inside a cell, viral nucleic acids take over
the cell and direct it to make more viral particles
Viruses are host-specific
 Only infect certain hosts
 Only infect certain cells


Have either DNA or RNA as their nucleic acid
(not both)
Smallest infectious agents known to humans
5/24/2017
VIRUSES

Viruses bind to the host and either
Inject its nucleic acid, or
Are engulfed through endocytosis


In either case, the protein coat is released
and the nucleic acid will replicate using
the machinery of the host cell.
Once new viral particles are assembled,
the host cell is destroyed and new viruses
are released to infect other cells.
5/24/2017
TYPICAL VIRUSES
5/24/2017
VIRUSES

One of the most recent infectious viruses
is HIV.
Only infects humans
Causes AIDS
claimed 22 million lives so far


HIV is a spherical virus containing RNA, a
protein shell, and an outer envelope
Estimated to be over 42,500,000 people
infected with the AIDS virus
5/24/2017
5/24/2017
VIROIDS



Similar to viruses, but consist only of a single
strand of RNA
None infect animals
Mainly infect cultivated crops
 Potatoes
 Tomatoes
 Cucumbers



Hard to detect
Stunted or distorted growth, may or may not
cause plant death
Spread very easily
5/24/2017
PRIONS



These are infectious proteins that can be
passed from one individual to another
Not species-specific – can be passed
between species
Examples include
scrapie in sheep and goats
mad cow disease in cattle (BSE)
chronic wasting disease in deer and elk
5/24/2017
PRIONS
Epidemic of mad cow disease in Great
Britain was apparently caused by the
spread of prions from sheep to cattle
 Prion-caused diseases in humans include:

Kuru – occurred in Papua New Guinea and
spread by eating the brains of their dead
Creutzfeldt-Jakob disease – transmitted by
surgical instruments and tissue transplants
Similar to mad cow disease
Causes holes in brain matter
5/24/2017
PRIONS


Do not reproduce or replicate as do viruses
and viroids
May cause a normal protein to change
shape to that of a dangerous protein
Proteins may stack up and interlock forming
plaques
Finally results in death
5/24/2017
CHAPTER 23
CLASSIFICATION OF ORGANISMS
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017
5/24/2017