Classifying the `Invisible` that we are unable to see without the aid of microscopes

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Oct 23, 2013 (3 years and 8 months ago)

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Classifying the `Invisible` that we are unable to see

without the aid of microscopes



SBI 3U


Section 2.1

pp.52
-

58

Recall:

Mitosis


cells

divide to

form

two cells

that are

identical to the

parent cell.


Meiosis


produces the

reproductive

cells (sperm &

egg) which have
half the number
of chromosomes
as the parent cell

A structure that contains strands of DNA or RNA

surrounded by a protective protein coat; it cannot

live independently outside of cells

Characteristics:


Are not cellular and don’t have cytoplasm, membrane
bound organelles or cell membranes.


Do not fit the 6
-
kingdom system (not ``alive``)


Outside of a living cell, a virus is a lifeless chemical
(dormant)


No life function on its own


Only when a virus invades a living cell, does it start to
reproduce and `come alive`

1) Size and shape
of

capsid
(outer protein layer that

surrounds the genetic material of a virus)

2) Types of diseases they cause.


Polio








Virus







HIV


Tobacco

Mosaic







T4

Virus







Virus

Viruses that infect and destroy bacterial cells (eaters

of bacteria) e.g. T4 Virus








Viruses undergo replication within a
host cell


Viruses use the
host cell

to produce multiple copies

of themselves.


This typical replication cycle of viruses is called the
LYTIC CYCLE


Lytic Cycle

is the replication process in viruses in

which the virus’s genetic material uses the copying

machinery of the host cell to make new viruses

However, sometimes the virus’s genetic material
enters the nucleus of the host cell becoming a
provirus. Replication will then occur through the


LYSOGENIC CYCLE


Lysogenic Cycle

is the replication process in viruses

In which the viral DNA enters the host cell’s

chromosome; it may remain dormant and later

activate and instruct the host cell to produce more

viruses

Lytic Cycle Viruses



Newly formed viruses burst form the host cell,
usually killing it.



In multicellular hosts, these newly formed viruses
infect neighbouring cells

RESULT: damage to host varies


Lysogenic Cycle Viruses (provirus)



Effects to the host might not be immediate


E.g. HIV (Human Immunodeficiency Virus) leads
to AIDS (Acquired immune deficiency syndrome)

Retrovirus’ contain an enzyme that causes the host

cell to copy viral RNA into DNA.


This DNA becomes a provirus that continues to

produce new viruses without destroying the cell


This process can continue for years, with no harm to
the host. However the provirus can separate from the
host chromosomes at any time and complete the more
damaging
lytic

cycle


Prions are infectious particles that causes damage to nerve

cells in the brain.



Prions are proteins that are normally found in the body



Disease causing agents that lack RNA or DNA


Prions seem to behave like a viral infection, BUT they are

NOT, as there is no RNA or DNA.


Disease results when prions change their molecular shape,
while maintaining their chemical composition and become
deadly.


Example:

Creutzfeldt
-
Jakob disease (CJD)




Bovine spongiform encephalopathy (BSE)




Scrapie in sheep

Viruses have the ability to enter host cells and direct

the activity of the host cell’s DNA


Genetic engineers are using viruses to introduce

specific genes into the host cell


1) Insert the gene into the genetic material of the
virus


2) Virus enters host cell and directs the cell to make
multiple copies of the virus


3) Each new virus in each new cell contains the added
gene



Learning Check, p. 55 #2, 5



Review Questions, p. 58 # 1


15


SBI 3U


Section 2.2

pp. 59


66


Bacteria and Archaea are more different from each other

than an apple tree is from a blue whale


Result



Three domains were established above the



kingdom rank





Domain Bacteria contains Kingdom Bacteria





Domain Archaea contains Kingdom Archaea

















Bacillus are rod shaped forms of Bacteria and
Archaea

Spherical forms are called

cocci

(plural) or
coccus

(singular)







Enterococcus


found in
intestines of warm
blooded animals

Rod forms are called bacilli (plural)

or bacillus (singular)







E.Coli



found in
intestines (cows), strain
0157 can lead to food
poisoning in humans

Spiral shaped







Streptococcus
bacteria are found

in chains of spheres






Some individual prokaryotic cells

(bacteria or archaea) group

together







Streptobacillus
bacteria are rod

shaped and found in chains

Archaea


process of methanogenesis to obtain

nutrients. Methanogenesis is an anaerobic process

that occurs in environments that lack oxygen


Some Archaea use sunlight as a source of metabolic

energy but no reliable evidence of photosynthesis.


Bacteria


some are photosynthetic


Example: Cyanobacteria use solar energy

to convert carbon dioxide and water into

sugar and oxygen.





Both archaea and bacteria occupy environments

with
oxygen (aerobic)
and without
oxygen

(anaerobic)


Archaea


ability to live in extreme environments

called extremophiles. Refer to Table 2.2 pg. 61


Bacteria


organisms that occupy environments

with moderate (less extreme) conditions called

mesophiles. There are few extremophilic bacteria.



















Prokaryotes reproduce through the asexual process of

binary fission


producing two genetically identical cells







The Genetic material in
prokaryotes is contained in a
single chromosome within
the cell. This chromosome is
replicated during binary
fission. When the cell reaches
a certain size, it elongates,
separating the original
chromosome and its copy. A
partition called a septum then
forms between the 2
chromosomes and the cell
splits.

Conjugation


there is transfer of genetic material (DNA),
involving two cells (prokaryotes), producing cells with new
genetic combinations thus increasing genetic diversity







Plasmids are small
loops of DNA that
are separate from the
main chromosome
and can also be
transferred.

A bridging structure
transfers DNA
material from one
cell to another

Endospores



dormant bacterial cells






able to survive for long periods during




extreme conditions

E.g. freezing or high temperatures, radiation & toxic chemicals)






A
Gram stain

is used

to divide bacteria into 2 groups





Gram
-
positive bacteria

have a

thick

protein layer on their cell

wall and
stain

purple.





Gram
-
negative bacteria
have a

thin

protein layer on their cell

wall and
stain

pink
.





Other methods used to identify bacteria and
archaea

include size and shape, nutrition (i.e. aerobic or anaerobic
processes), movement and genetic components.
Biologists prefer techniques that rely on DNA
comparisons.





B)
Streptococcus

pygones

is a

Gram
-
positive

bacterium that

causes strep

throat infections




A)
Clostridium

botulinum

is an

anaerobic bacterium

that can cause

illness in humans




C)
Streptococcus

mutans

is a Gram

positive

bacterium

that causes tooth

decay






Learning Check, p. 62 #7


12



Review Questions, p. 66 # 2


9, 11


12





SBI 3U


Section 2.3

pp.67
-

71

The theory that says eukaryotic cells evolved from a
prokaryotic cell engulfing one or more different
prokaryotic cells. The engulfed cells survived and
became an internal part of the engulfing cell

Theory suggests that mitochondria and chloroplasts

were once small, free
-
living prokaryotes.


When they were engulfed by other, larger cells, they

remained intact and continued to function, benefitting the host

cell.


Endosymbiont


a cell that is engulfed by another cell in

endosymbiosis


Host cell


a cell that engulfs another cell in endosymbiosis





Similar features between chloroplasts, mitochondria

and prokaryotes




Membranes




Ribosome's




Circular chromosome




Gene sequences




Divide by binary fission



Hypothesis


first multicellular organisms arose

from colonies created by diving individual cells.


Genes within these cells carried instructions to

become specialized for different functions.


Example: Some cell groups became specialized in

absorbing nutrients, while others became specialized in

gathering information from the surrounding

environment





Learning Check, p. 69 #13


17



Review Questions, p. 71 # 1, 4, 6


9



QUIZ COMING UP SOON on ‘MICROBIOLOGY’



Assessment
NEXT CLASS:
Measles Immunization
Graphing Activity (you need your textbook!)



SBI 3U


Section 2.4

pp.72
-

78


A eukaryotic organism, usually

unicellular, that is not a fungus, plant or

animal




e.g. Amoeba




Eukaryotes




Most are unicellular




Most are aerobic (need O
2
)




Some are motile(able to move), some have
pigments




Placed in this kingdom because they do not fit
well in other kingdoms




Not very similar or closely related to one
another






often called
protozoans



Heterotrophs, live in aquatic environ.



4 main classes



many species are parasites

cause diseases


Parasite


an organism that benefits by

living in or on another organism



Cell membrane, no cell
wall


Move and create different
forms (change shape)


Live in water, mud and a
few in living animal hosts

Example:
Amoeba

Pseudopods

(false feet) are

temporary

finger
-
like

projections used

for both feeding

and movement


Short, hair
-
like projections that cover the surface
of the cell, called cilia


Cilia aids in movement and sweeping food
particles into cell


Large, complex, some are parasites

Example:
Paramecium


Have one or more flagella (long, hair
-
like
projection that propels the cell)


Hard protective covering over membrane


Some parasitic, some
mutualistic

Example:
Trichonympha

A
mutualistic

relationship is a
relationship where
both organisms benefit


Entirely parasitic, taking nutrients from the
animal host

Example:
Plasmodium vivax

causes malaria in humans


Heterotrophs



Absorb nutrients from living
organisms, dead organisms and
wastes



Produce spores (reproductive
structures) like fungi



Glide for motility


Examples: Slime moulds, water




moulds


contain pigments like chlorophyll



photosynthetic



once classified as plants but lack
leaves, stems and roots.



3 main classes


Examples:
phytoplankton


Single
-
celled



Free
-
floating aquatic organisms



Source of food for larger marine
organisms


Example:
Phytoplankton

Different

diatoms


Two flagella at right angles, produce twirling
motion



Some are found in reef
-
building corals but are
fast losing this habitat due to climate change.



Quick reproduction leads to an algal bloom


Example:
Gonyaulax catenella

Red

Tide


Found in shallow fresh water, have a flagella



Autotrophs in sunlight & heterotrophs in the
dark



have a light
-
detecting structure to orient
themselves


Example:
Euglena gracilis



Learning Check, p. 76 #19


21



Review Questions, p. 78 # 1, 3, 5


8, 10



Chapter 2 Self Assessment, Pg. 86
-
87 #1
-
2, 4
-
7, 9
-
10, 11
-
14, 17
-
22