Download Chapter 7 - Heritage Christian School

Chapter 7. Taxonomy and Viruses
taxonomy • an artificial* system of classifying organisms according the inferred
(presumed) relationships among organisms.
• the premise is that the more features two organisms have in
common, the closer they are related.
***artificial because it is an invention of man. This implies that its validity is open to
question.
the purpose:
• to assist in the identifying of organisms.
• to provide a basis for recognizing natural groupings of living
things.
Binomial nomenclature - Carolus Linnaeus (1707-1778)
• the scientific name given to organisms made up of it’s genus
(pl.genera) and species name. Commonly the names are Latin or
Greek which in themselves provide some description of the
organism…if you understand Greek and Latin that is!
e.g. Castor canadiensis - beaver
Acer rubrum - red maple
(What do you suppose ‘canadiensis’ refers to?…
…how about ‘rubrum’)
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Genus
Species
Common name
Ursa
americanus
American black bear
Ursa
horribilis
Grizzly
Ursa
arctos
Alaskan brown bear
Ursa
maritimus
Polar bear
Ailuropoda
melanoleuca
Panda
Phasocolarctos
cinereus
Koala
From the table, what would you assume about the relationships
between these ‘bears’?
dichotomous key - a series of two answer questions, which when
followed to completion serves to determine the identity of an
organism. The process is commonly referred to as ‘keying out’ an
organism.
(…So if you want to impress someone, you say,”Sorry I can’t go to
the movies tonight. I have to spend some quality time in the lab and
‘key out’ some insects.”
Usually, they become awestruck and ask if they can come
too…either that or tell you that you need to get a life.)
e.g. Insect key in Peterson’s Field Guide
Levels of Classification
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Taxa
Kingdom
dandelion
Plantae
housefly
Animalia
human
Animalia
Phylum
Tracheophyta
Arthropoda
Chordata
Class
Angiospermae
Insecta
Mammalia
Order
Asterates
Diptera
Primates
Family
Compositae
Muscidae
Hominidae
Genus
Taraxacum
Musca
Homo
Species
officinale
domestica
sapiens
The Five Kingdom System of Classification
All living organisms can be catagorized into one of five different
kingdoms.
Monera - single celled prokaryotes (anything lacking nuclei).
E.g. Bacteria and cyanobacteria (blue-green algae)
Protista - single (and some multi-) celled eukaryotes (have nuclei)
E.g. Protozoa and simple algae.
Fungi - multicellular (usually) heterotrophs (get nourishment from
some other source).
E.g. Mushrooms, molds, yeast
Plantae - multicellular autotrophs (photosynthetic)
E.g. Seaweeds, mosses, ferns, conifers, flowering plants
Animalia - multicellular heterotrophs
E.g. You, me, kitty, puppy, and goldy (you know…the fish)
The Phylogenic Tree
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A schematic diagram representing inferred relationships between
organisms…assumes macro-evolution from common ancestor.
Figure 7.4
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Viruses
biological particle incapable of reproduction on its own. Once inside a
living cell it reproduces.
Non-living yet reproduces (maybe best thought of as somewhere
between living and non-living.)
Extremely small - 20 to 400 nm. Extremely simple ‘anatomy’; only a
small piece of single or double stranded DNA or RNA (but not both)
in a protein capsid. Capsid amounts to ~95% of the virus and gives
the virus it’s particular shape.
Tobacco mozaic virus Adenovirus Bacteriophage.
Sometimes has an outer lipid membrane believed to be ‘inherited’
from the host cell membrane.
Not all viruses are disease causing.
Viruses can be quite specific (selective) to the types of cells that they
infect. Some infect only plant, only animal or only bacteria.
Wide ranges:
swine flu virus
hogs and humans
rabies virus
rodents,dogs, humans and others
Narrow ranges:
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human cold virus
cells of upper respiratory tract
AIDS virus
certain types of white blood cells
Some bacteriophages infect only bacteria in a very narrow range.
This appears to indicate that the bacteria might be related.
Viral Replication
There are two strategies by which viruses replicate:
◊ Lytic - a very quick replication whereby the nucleic acid (DNA or
RNA) is injected into the host cell; the host cell replication
machinery is hijacked and multiple copies of virusees are
produced within about 25 - 45 minutes. Host cell bursts (lysis)
spreading new viruses everywhere. This is considered a virulent
reproduction.
◊ Lysogenic - a very slow replication where the virus DNA/RNA is
inserted into host DNA and replicated as part of the normal host
life cycle. The virus remains dormant until some signal causes it to
enter the lytic cycle. Lysogenic is considered a temperate
reproduction.
***prophage - the term given to the viral DNA/RNA when it is in
dormant stage.
Figure 7.7
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Immune Defence System
The human immune system can be divided into two main
components:
non-specific defences - these are general means which resist all
types of pathogens. (a.k.a. ‘baddies’)
included are:
skin - physical barrier
oil/sweat glands - acidic barrier which kills many pathogens
ciliated mucous membranes - physical sweepers of airborne
pathogens
gastric fluid - acid/chemical barrier against food-borne pathogens
natural bacteria flora - act as surface competition for foreign bacteria
macrophages - act like Pac-man in the blood to gobble up foreign
bodies
complement system - 20 plasma proteins which act like tag-alongs on
foreign bodies so macrophages can find them faster.
Specific Defences a very complex system in which the presence of a pathogen causes
antibody production, which aids in the response. The problem is that
it takes some time for this production to occur. Once it does though,
the body can deal with the invader. The cool thing is that some of the
antibodies are then stored in the lymphatic system so if that SAME
pathogen infects a second time, the immune response will be fast,
fast, fast! Look out pathogen, ‘cuz it will be Bam! Kapow!
Viral Diseases
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A few definitions:
◊ endemic - when the pathogen is with us all the time (common
cold)
◊ epidemic - when disease spreads rapidly (some of the annual
influenza outbreaks)
◊ pandemic- when the disease spreads so rapidly that it becomes a
global problem (AIDS)
◊ oncogenic viruses - cancer caused by viruses inserting specific
genes into a cell.
◊ interferons - a chemical produced by the body which
INTERFERES with the viruses’ ability to infect other cells.
◊ viroids - free RNA…wipe out seed potatoes
◊ prions - protein coats with no nucleic acid…slow fatal CNS
disease in humans
Some other examples:
◊ polio(myelitis)
◊ small pox
◊ measles
Phylogeny - in other words: if your an evolutionist, Where did they
come from. Nobody knows, but there are a few ideas.
Viruses:
• were once unicellular parasites, but didn’t need there organelles,
so they lost them. (even evolutionists have problems with this one)
• were once ‘free-living pre-cells(?) that later became parasites of
cellular organisms. (this one too)
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• were fragments of DNA from some ancestral cell. (most figure this
would be more likely)
What is Gene Therapy?
Read p.205
vector - in biology it is some sort of carrier. For example, mosquitoes
are vectors for malaria.
Virus
Viral
DNA
removed
Target DNA
inserted
Patient's
immune deficient
Reinjected
white blood
cells
into
patient
Target DNA
is replicated
as
cell divides &
becomes part
Immune
defifiency
is overridden
of patients
DNA
Review Questions p 205
Chapter Review
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