Review test questions

Classification Test In examining a cell in an electron

microscope, you observe that the cell has a nucleus and a cell membrane but no cell wall. You conclude that the cell probably comes from a(n) sea-weed plant fungus animal

Birds and snakes share a common ancestor from over 250 million years ago, but now they show many physical differences. These differences are most directly the result of coevolution between species. molecular clocks ticking at different rates. the long-term accumulation of mutations. differences in the alleles of the ancestor.

Which scientific advancement enabled the discovery of differences between prokaryotes and eukaryotes? Light microscope Electron microscope Computers DNA analysis

Based on the given characteristics, this organism would be classified in which kingdom? Bacteria Fungi Plantae Protists

Chapters 18 & 31 Viruses, Bacteria &

Immunity

What is a virus? Virus – a very

small, nonliving particle that can cause disease

What are some diseases that are caused by viruses?

Influenza RubellaCommon cold MumpsChicken pox MeaslesHerpes Small poxAIDS Viral hepatitisShingles RabiesGastroenteritis Cold soresMononucleosis Ebola

Many viruses affect humans!Next slide: Beware if you are squeamish

SmallpoxChicken pox

Measles

Girl infected with smallpox in Bangladesh, 1973

WHO certified eradication of Smallpox in 1979

How are viruses spread? Air Direct physical contact Body fluids Vector - a carrier of an infectious agent

Examples: insect, rodent, monkey…

Viruses are found in the air, soil, and water!

Viruses can attack animals, plants, and bacteria!

BacteriophageAnimal Virus

Plant Virus

Bacteriophage

Influenza

Tobacco mosaic virus

Are viruses alive?

They DO have an orderly structure with genetic material.

They DO produce offspring, but not on their own!

They DO respond to the environment.

3 Criteria of Life They DO NOT respire They DO NOT grow They DO NOT move

In fact, all viruses can do is reproduce, and they can’t even do that alone!

Host cell – a living cell that a virus uses to reproduce.

Anatomy of a Virus Outer coat of protein Inner core of nucleic acid

Contains the viruses’ genetic material Can be RNA or DNA

This simplicity allows it to be very efficient at reproducing.

Viral reproduction

Lytic Cycle

1. Virus attaches to host cell and injects its genetic material

2. Host cell DNA is destroyed

3. New viruses are formed

4. Host cell bursts (lyses), releasing the viruses and killing the host cell

Lysogenic Cycle

1. The virus DNA (RNA) becomes part of the host cell’s DNA

2. The host cells reproduce normally with the virus DNA hidden in each new daughter cell.

3. Host cell is not killed until lytic cycle is entered

Viral reproduction

How can viral diseases be cured?

Many cannot be “cured” because they are constantly evolving.

The body gets rid of viruses through the immune system.

Many can be treated with antiviral drugs to keep symptoms under control.

What is a vaccine?

Vaccine - substance that contains parts of dead or weakened microbes. Vaccines cause your body to make antibodies

that will recognize and destroy the virus if it enters the body in the future.

Vaccines can prevent illness from happening.

Personal Health Issues The vaccine cannot cause the disease but

may produce a non-specific response at the site of the shot.

Swelling or redness at the site of the injection.

Some individuals may still get the disease after vaccination. Average flu vaccine effectiveness is 60%

Public Health Issues Vaccines can protect the people who

receive them and those around them. Creates “herd immunity”. Smallpox eradicated due to mandatory

vaccination. Used to have 13,000-20,000 cases each year in the US.

Type B meningitis, polio, diphtheria and measles are now rare.

Public Health Issues People underestimate the dangers of not

vaccinating against disease. A small trend away from vaccinations puts

people at risk. A resurgence of some diseases is occurring

because vaccinations rate are too low to provide the herd immunity.

How can viruses be helpful? Viruses may help cure

other diseases through gene therapy.

Other Types of Viruses Prions - composed of proteins, but no nucleic

acids. Act on other proteins causing them to fold improperly.

Example: Mad cow disease, Creutzfeldt-Jakob disease

Plant Viruses - Do not undergo lytic or lysogenic cycle

Example: Tobacco mosaic virus

Bacteria

The smallest and simplest living things

Intro to Bacteria

Bacteria: Two Kingdoms

1. Archaea (Archaebacteria): Found in three extreme habitats

Methanogens - Oxygen free environments Halophiles - Very salty environments Thermophiles - Extremely hot, acidic

waters

Yellowstone National Park – hot springs

2. Bacteria (Eubacteria): Found in many environments and live a variety of lifestyles.

EverywhereCyanobacteriaAnimal intestines

Salmonella

Soil Pseudomonas

Means of acquiring food

Heterotrophs – feed on other organisms

Saprobes – feed on dead things, important decomposers

Autotrophs – make their own foodPhotosynthesis or Chemosynthesis

Identifying Bacteria

Three most common cell shapes:

Cocci – Spheres

Bacilli – Rods

Spirilla – Spirals

Identifying BacteriaArrangement: Diplo – Pairs

Staphylo – Grape-like clusters

Strepto – Long chains

Identifying Bacteria

So what would a “Streptospirilla” look like?

Long chains of spirals

Diversity of Metabolism

Obligate Aerobes - bacteria that require oxygen for cellular respiration.

Example: Mycobacterium tuberculosis

Diversity of Metabolism

Obligate Anaerobes - bacteria that cannot use oxygen and are killed by it.

Example: Tetanus, botulism

Deep wounds are hard to clean and provide ideal conditions for growth of anaerobes.

Clostridium botulinum: Causes food poisoning

Botox injections comes from C. botulinum

Adaptations for Survival

Endospores - hard outer covering, resistant to drying out, boiling, and many chemicals.

Bacteria form endospores when environmental conditions are unfavorable.

During this time, no growth or reproduction takes place.

Have been found to germinate after thousands of years.

Endospore

Bacterial Reproduction:

Binary Fission asexual reproduction Cell grows larger, copies its chromosome

and then the cell divides in half. Daughter cells are genetically identical to

each other and to the parent cell.

Bacterial Reproduction:

Conjugation Sexual reproduction One bacterium transfers all or part of its

chromosome to another cell through a pilus (bridge like structure) that connects the two cells.

Beneficial bacteria

1.Decomposers2.Nitrogen fixers3.Help digestive processes

Rhizobium in root nodules

Harmful bacteria

Human pathogens: Diptheria Typhoid Tetanus Leprosy TB Plague Strept. Throat

Plague

Tuberculosis – lung tissue

Ways to fight or prevent problem bacteria

Sterilization – medical equipment Pasteurization – milk Vaccinations – DPT Antibiotics – Penicillin

Discovered by Alexander Fleming in 1929, while observing mold growing in a petri dish

Penicillin

Antibiotics A variety of drugs that kill bacteria usually

by destroying the cell wall or by preventing them from reproducing. Antibiotics do not help with viral infections like the flu or cold viruses.

Personal Health Issues Some people are allergic to certain

antibiotic types like penicillin. Antibiotics kill good bacteria in your body as

well as the bad. This may allow fungal infections to take hold.

Doctors recommend eating yogurt after you finish all your antibiotics.

Public Health Issues Overuse and improper use of antibiotics

has resulted in many strains of antibiotic resistant bacteria.

Patients must take the full course of antibiotics even if they start feeling better.

80% of antibiotics used in the US are given to livestock.

Immune SystemChapter 31

Germ Theory BC 7000 – Spirits: drilling of holes in peoples

heads to release evil sprits that cause disease. BC 460-1800s – Humors: fluids called humors

thought to cause disease (blood letting). AD 1330-1352 – Herbal: attempt to use incense

to cure the Black Death. 1857 – Germ Theory – Louis Pasteur

hypothesized that disease is caused by small “animals” (microbes)

George Washington – Blood letting

Pathogens A pathogen is a disease causing micro-

organism. Bacteria – E. coli Viruses – cold, flu Fungi – athlete’s foot Protists - malaria Parasites – parasitic worms

First Lines of Defense The first line of defense are barriers to keep

pathogens out of the body.

1. Physical Barriers – skin, natural bacteria

2. Mechanical barriers – cilia, mucus, tears

3. Chemical barriers – pH of urine, gastric juices, vaginal tract.

Second Line of Defense The non-specific responses that the body

uses for all pathogens. Response is quick.

1. Phagocyte

2. Fever

3. Swelling

Phagocyte

Third Line of Defense Specific response for specific pathogens.

1. B Cells (white blood cell)

2. T Cells (white blood cell)

3. Phagocytes (white blood cell)

4. Antibodies (proteins)

Antibody

Allergies An allergy is an oversensitivity to a normally

harmless antigen.

Lifestyle Choices and Health Some lifestyle choices can prevent chronic

diseases and keep your immune system working at its best.

Regular exercise Healthy diet No smoking Sufficient sleep