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LS Topic 1/Lesson 3 Notes

 About Viruses

A virus is defined as any of a various number of submicroscopic parasites that can infect any animal, plant or bacteria and often lead to very serious or even deadly diseases.

A virus consists of a core of RNA or DNA, generally surrounded by a protein coat.

A virus can NOT replicate without the help of a host cell, and though they can be spread, viruses lack the ability of self-reproduction and are not always considered to be living organisms in the regular sense.

Some of the most common or best known viruses include the human immunodeficiency virus (HIV), which is the virus that causes AIDS, the herpes simplex virus, which causes cold sores, smallpox, multiple sclerosis, and the human papilloma virus, now believed to be a leading cause of cervical cancer in adult women. The common human cold is also caused by a virus.

Since a great deal of mystery still surrounds the origins of most modern viruses, ways to cure these viruses and the diseases they cause are still in the very early stages of development.

A Vaccine is a substance introduced to the body to stimulate the production of chemicals that destroy specific disease-causing viruses and organisms. A viral vaccine may be made from weakened or altered viruses.

It triggers the body’s natural defenses and puts the body “on alert”.

Bacteria are among the smallest living organisms, but they usually band together in colonies. Bacteria can be autotrophic, make their own food, or heterotrophic, feed off of other organisms.

 

 

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Cell Design

Bacteria cells are unicellular and prokaryotic. They have a cell wall, cell membrane, free – floating DNA, cytoplasm, ribosome, and cilia or flagella. Bacteria are classified into three different shapes – 

coccus (round), bacillus (rod), and spirillum (spiral).

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   Two Branches of Bacteria

1.     Archeobacteria is the oldest type of bacteria. They live in acidic water, sulfur hot springs and extremely salty water. Only found in inhospitable environments.

2.     Eubacteria is the most common type of bacteria, today. It is also found everywhere.

 

   Adaptations to an Environment

An endospore is a copy of the bacteria’s DNA and a little cytoplasm in a resistant form. It can resist heat, dry conditions, radiation, and boiling. Bacteria cells also produce plasmids. A plasmid is a small loop of DNA that can be transmitted to other bacteria cells. Plasmids are useful because they can be resistant to antibiotics.

 

   Uses by Man

            Man has found uses for different types of bacteria, such as 

         antibiotics, food manufacturing, and some insect pesticides.  

         Bacteria are also used to purify sewage treatment plants.

 

   

     Three Types of Heterotrophic Bacteria

1.     Parasites – obtain nutrients by living in or on organisms.

2.     Saprobes – feed off of the waste of other organisms.

3.    Decomposers – feed off of dead organisms.

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o Leptospina – causes disease in livestock.

o Streptococcus – kills white blood cells and causes strep throat and scarlet fever.

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o Escherichia coli – causes food poisoning.

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o Lactobacillus – causes tooth decay.

o Bacillus anthracis – anthrax in sheep and humans.

o Staphylococcus – staph infections.

o Clostriclium tetani – tetanus in humans.

o Streptomycin – used in life saving medicines.

 

   Decomposition

Bacteria, such as saprobes and decomposers, feed off of dead organisms or the wastes of organisms. They release nutrients back into the soil so that plants can use them.

 

 

   Fermentation

Bacteria are used in making alcoholic beverages and cheese.

 

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Binary Fission

A bacteria cell reproduces by binary fission. The cell makes a copy of its DNA then divides into two separate cells. Asexual Reproduction

Section 3 Protists (See lab and worksheets)

Section 4 Fungi

Fungi are eukaryotes that have cell walls, are heterotrophs that feed by absorbing their food, and use spores to reproduce.

Hyphae – are branching threadlike tubes that make up the bodies of Multicellular fungi.

They use spores to reproduce. They can reproduce both sexually and asexually.

Asexual reproduction – no partner is needed. The organism makes an exact copy of itself.

Unicellular yeast cells undergo a form of asexual reproduction called Budding. These cells grow from the body of a parent cells similar to a bud on a tree.

Roles Fungi play are;

• Food for people

• Decomposers and recyclers on Earth

• Some cause disease

• Some live in symbiosis with other organisms.

Lichens consist of fungus and either algae or autotrophic bacteria that live together in a mutualistic relationship.

Lichens are irregular, flat, crusty patches that grow on tree barks or rocks.

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