Transcript Virus and Kingdom Overview

CHAPTER 20 CLASSIFICATION:
Kingdom Overview and Virus Notes
VIRUSES
 Noncellular,
infectious agents
composed of a nucleic acid inside
a protein coat.
 They lack many features of living
cells, so they are in a category of
their own somewhere between
living and nonliving.
 A virus cannot reproduce itself; it
can only be reproduced inside of a
host cell.
THEY ARE LIKE LIVING ORGANISMS IN
THAT:
They possess genetic material
 They are composed of nucleic acids, which can be
DNA or RNA
 They are capable of mutation – they can evolve
and adapt to their environment
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THEY ARE UNLIKE LIVING
ORGANISMS IN THAT:
They are not made of cells
 They have NO ribosomes (for protein synthesis)
 They have NO metabolic machinery for protein
synthesis or energy generation
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OTHER CHARACTERISTICS:
Viruses take over and use a cell’s machinery
 Viruses do not grow
 They are not considered living and are not in any
of the kingdoms
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VIRAL MULTIPLICATION (5 STEPS)
Attachment
- virus attaches to
a host cell
Penetration
- either the virus
or its genetic material will enter
the cell
Replication
and Synthesis - the
genetic material directs the host
cell into producing copies of viral
nucleic acids and proteins
Assembly
- viral nucleic acids
and proteins are assembled into
new viruses
Release
- new viruses release
from the cell
RETROVIRUSES
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The genetic material of retroviruses consists of
ribonucleic acid (RNA), instead of
deoxyribonucleic acid (DNA).
Retroviruses are unique in that they reproduce
by transcribing themselves into DNA.
 Reverse transcriptase, an enzyme within a
retrovirus, makes it possible for the retrovirus’
RNA to perform as a template of sorts for the
transcription process.
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Once transcription has taken place, the viral
DNA gains access to the DNA of a cell,
reproducing along with the cell and its offspring.
 Within the cell’s offspring, referred to as
daughter cells, the viral DNA creates RNA
replicas of itself.
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Finally, the RNA replicas leave the daughter
cells after coating themselves with a protein.
Have been known to lead to cancer
 Also the cause of HIV which leads to AIDS.
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Retroviruses are prone to mutation.
 For this reason, viruses in this family often
become resistant to antiviral drugs within a
relatively short period of time.
 This level of mutability is one of the reasons
cited for the difficulty scientists face in trying to
develop a safe and effective HIV vaccine.
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PROKARYOTAE
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Lack nuclear membranes,
mitochondria, chloroplasts, and other
membrane bound organelles.
Divide & reproduce without meiosis.
DNA is one circular double helix called
a plasmid.
Has no chromosomes
Example: Some bacteria
PROTISTA
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Microscopic organisms common in
fresh & salt water.
Live most places that are moist.
Cause diseases such as malaria,
dysentery, & sleeping sickness
Most protista are harmless.
They are eukaryotes.
Some bacteria fall in this category
along with amoebas, euglenas, and
diatoms
FUNGI
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Mushrooms, toadstools, rusts,
molds, yeasts
Have cell walls
Heterotrophs – cannot make
their own food.
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Most are decomposers – get
food from dead matter.
PLANTAE
Eukaryotic
Autotrophs
Have
cell walls and chloroplasts
Nonmotile (can’t move)
Most contain chlorophyll
Undergo photosynthesis
Depend on water & air for
nutrients
ANIMALIA
Multicellular & very diverse
 Most are motile
 Heterotrophs
 Divided into two main categories –
vertebrates & invertebrates.
 Invertebrate – no backbone
 Vertebrates – have backbones
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