Science Test Review (Chapter 2; Lessons 1, 2 & 3)

Vocabulary

1. virus - a tiny, non living particle that enters and then reproduces inside a living cell
2. host - an organism that a parasite lives with, in, or on, and provides a source of energy or a suitable environment for the parasite to live
3. parasite - an organism that benefits by living with, on, or in a host in a paratism interaction
4. vaccine - a substance used in a vaccination that consists of pathogens that have been weakened or killed but can still trigger the body to produce chemicals that destroy the pathogens
5. bacteria - single-celled organisms that lack a nucleus; prokaryotes, it has circular shaped DNA
6. cytoplasm - the thick fluid region located inside the cell membrane (in prokaryotes) or between the cell membrane and nucleus (in eukaryotes)
7. ribosome - a small grain-shaped organelle in the cytoplasm of a cell that produces proteins
8. flagellum - a long, whiplike structure that helps a cell move
9. celular respirsration - the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen (krebs cycle)
10. binary fission - a form of asexual reproduction in which one cell divides, forming two identical cells
11. conjugation - a form of sexual reproduction in which a unicellular organism transfers some of its genetic material to another unicellular organism
12. endospore - a structure produced by prokaryotes, such as bacteria, in unfavorable conditions; a thick wall encloses the DNA and some of the cytoplasm
13. pasteurization - a process of heating food to a temperature that is high enough to kill most harmful bacteria without changing the taste of the food, named after its inventor, Louis Pasteur
14. decomposer - an organism that gets energy by breaking down wastes and dead organisms, and returns raw materials to the soil and water
15. protist - a eukaryotic organism that cannot be classified as an animal, plant, or fungus
16. protozoan - a unicellular, animal-like protist
17. pseudopod - a "false foot" or temporary bulge of cytoplasm used for feeding and movement in some protozoans
18. contractile vacuole - the cell structure that collects extra water from the cytoplasm and expels it from the cell
19. cilia - tiny, hairlike projections on the outside of cells that move in a wavelike manner
20. algae - plantlike protists
21. pigment - a colored chemical compound that absorbs light
22. spore - in bacteria, protists and fungi, a thick-walled, tiny cell capable of surviving unfavorable conditions and then growing into a new organism

Viruses

• Viruses are tiny, nonliving particles that enter and reproduce inside a living cell. 
• Viruses are nonliving and have a protein coat that protects an inner core of genetic material. They're considered nonliving because they don't have cells and don't use their own energy to grow or respond.
• Viruses cannot make food, take in food, or produce wastes.
• All viruses cause disease.
• They are not classified as organisms.
• The only life activity performed by them is reproduction.
• They are made of DNA or RNA (core) and an outer coat of protection.
• Some diseases caused by viruses are:
  • common cold
  • chicken pox
  • smallpox
  • Polio
  • cervical cancer
  • viral meningitis
  • Flu
  • Dengue
• Viruses reproduce inside a host: living cell or organism. They cannot reproduce alone.
• Viral diseases are prevented by inoculating people and animals with vaccines.
• The virus takes over the cells' functions. Some instantly, while others take time.
• When viruses reproduce they inject their genetic material into a cell. The genetic material makes copies of itself, is released and invades other cells to continue this process. Most viruses destroy the cells in which they multiply.
• The human body produces a substance called interferon to combat viral infections.
• Vaccines have weakened viruses to provoke the formation of antibodies.
• Viruses vary in shape, they may be:
• round
• rod-shaped
• brick shaped
• bullet shaped
• robotlike shaped (bacteriophage)
• A bacteriophage is a virus that infects bacteria. Its name means "bacteria eater". It has a robotlike shape.
• Viruses are smaller than cells. They can't be seen under the microscopes you use in school. They're measures in nanometers (nm), which are billionths of meters. 
• The smallest viruses are about 20 nanometers in diameter, while the largest ones may be up to 200 nanometers in diameter.
• The average virus is quite small, even compared with the smallest cells (bacteria).
• Scientists don't use two-part names with viruses because they aren't organisms. They may be named in different ways, like:
• for the disease the cause (poliovirus)
• for the area where they were discovered (The West Nile Virus)
• Although all viruses have similar structures, their surface cells are different. Surface cells act as keys for the locks of the cells, which are the cell's surface proteins.
• A common cold virus may be compatible with the cells in the human nose and throat.
• Viruses may affect all living organisms, not just humans.
• An apple tree infected with the mosaic virus may produce less fruit.
• Dogs and cats get deadly viral diseases such as rabies and distemper.
• Gene therapy is when scientists take advantage of a virus' ability to enter a host cell. They use a virus as a "messenger service" to deliver genetic material to cells that need it. Gene therapy can be used to treat diseases such as:
• cystic fibrosis - people with this lack the genetic material to keep their lungs functioning properly

Bacteria

• Bacteria were first discovered in the late 1600s by a Dutch merchant named Anton von Leeuwenhoek, who made microscopes as a hobby. One day he noticed small wormlike organisms while looking at scrapings of his teeth.
• Bacteria live almost everywhere, but you cannot see them at simple sight, you must see them under a microscope.
• There are more bacteria in your mouth than there are people in the world.
• Bacteria are organisms that have:
• no nucleus (prokaryotes).
• DNA (circular in shape).
• Bacterial cells have characteristics which include the following:
• are surrounded by a rigid cell wall for protection
• have a cell membrane, which controls what goes out and comes in
• have ribosomes, which produce proteins, on the cytoplasm
• may have a flagellum (long, whiplike structure that helps a cell move)
• Not all bacteria cause disease, some are necessary for our own well-being. Bacteria are involved in oxygen and food production, in health maintenance and medicine production and in environmental cleanup or recycling. Some foods are prepared using bacteria:
  • yogurt
  • some cheeses
  • sausages
  • pickles
• Bacteria may live in many types of environments, even extreme ones.
• They are classified by their shape into categories:
  • coccus - round
  • bacilli - oval
  • spirilla - spiral
• Some examples of diseases caused by bacteria are:
  • dental cavities
  • tetanus (lockjaw)
  • botulism
  • strep throat
  • Tuberculosis
• Bacteria may reproduce every 20 minutes if they have the right conditions (temperature, moisture and food).
• Infections caused by bacteria are treated with antibiotics.
• Bacteria vary greatly in size, they're measured in micrometers (millionths of meters) and usually measure about 0.5 - 1 micrometer in diameter. Bacteria are bigger than viruses.
• Bacteria get energy by making food (some are autotrophs) or eating other organisms (heterotrophs).
• Bacteria convert food into energy via a process called cellular respiration, or the krebs cycle. Most bacteria need oxygen for this process, but not all of them since some bacterias die if oxygen is in their surroundings.
• Bacteria are also classified by the conditions or places where they may live:
  • Archaebacteria (Extreme Conditions)
  • Eubacteria
• They may reproduce sexually or asexually:
• Asexual reproduction is called binary fission, in this process one cell divides to form two identical cells. Bacteria grow up to twice its size to prepare for binary fission. The genetic material splits into two separate cells, therefore the offspring is genetically identical to the parent. Binary fission increases the number of bacteria.
• They may reproduce sexually via conjugation, which is the bacterium's transfer of genetic material through a thin, threadlike bridge. After the transfer the bacteria separate and as a result the bacteria obtain a combination of genetic materials. Conjugation does not increase the number of bacteria.
• When bacteria are in danger, they develop an outer protective covering called endospore. An endospore is a small, rounded, thick-walled resting cell that forms inside a bacteria cell. It encloses the cell's genetic material and some of its cytoplasm. Endospores survive for many years in harsh conditions. Since they're very light, they wait for the breeze to carry them to a new place where conditions are favorable and it opens up. The bacterium begins to grow and multiply.
• Some bacteria in soil are decomposers, they clean the environment. They're called "nature's recyclers".

Protists

• Organisms with characteristics of plants and animals are called protists. They're very diverse.
• All protists are eukaryotes. (have nucleus)
• Can be autotrophs or heterotrophs.
• Most are unicellular, but some are multicellular.
• Some cannot move, others can.
• Due to protists' diversity scientists divide them into three groups:
• animal-like protists (protozoans)
• are unicellular
• may have pseudopod, flagella, cilia
• may have a contractile vacuole (expels excess water) 
• protozoans with cilia have two nuclei, the small one takes care of reproductions and the larger one of everyday tasks in the cell
• protozoa may be disease causing parasites
• plant-like protists (algae)
• are autotrophs
• can be unicellular or multicellular
• use pigments to capture the sun's energy (exist in variety of colors)
• are an important food source
• fungus-like protists
• are heterotrophs
• have cell walls
• use spores to reproduce (tiny cells that are able to grow into a new organism)
• Examples of diseases caused by some Protozoa:
• Plasmodium - Malaria
• Entamoeba histolytica - Amoebic Dysentery
• Facciola Hepática - Liver conditions (Fascioliasis)
• There are many types of algae, or plant-like protists. These are:
• euglenoids
• green and unicellular
• found in freshwater
• most are autotrophs
• dinoflagellates
• unicellular in various colors
• have two flagella
• can light up when disturbed
• diatoms
• unicellular with glasslike walls
• when they die and pile up they make diatomaceous earth, which is good for household polishing
• red algae
• mostly multicellular seaweeds
• large absorb small amounts of light
• makes carrageenan, which is good for ice cream and conditioner
• is eaten by people in Asia
• brown algae
• multicellular seaweeds
• have holdfasts which anchor them to the ground
• float upright because of the gas they have in the bladder
• algins are extracted from it and used as a thickener in puddings
• There are three types of fungus-like protists, they are:
• slime molds
• brilliantly colored
• live in moist and shady places
• feed on bacteria and other microorganisms
• water molds and downy mildews
• live in water and moist places
• often grow as tiny threads that look like fuzz
• attack many food crops (potatoes, corn, grapes...)
• Plant-like protists may have chloroplasts and a cell wall.
• Some examples of protists are:
• • Amoeba
  • Paramecium
  • Euglenoids
  • Diatoms
• Amoeba surround food and enclose it in a vacuole.

NOTE: THIS REVIEW ONLY INCLUDES CHAPTERS 1 THROUGH 3, IT IS HIGHLY RECOMMENDED YOU READ CHAPTER 4 AND STUDY FROM YOUR NOTES. YOU SHOULD ALSO READ LESSONS 1-3.