Thursday, October 25, 2007
Viruses are non-living particles that affect all living things by spreading disease. Some familiar viral infections include: the common cold (my ailment of the week), influenza, measles, chicken pox, small pox, HIV, polio, ebola and many, many more.
Why are viruses not considered to be organisms? Viruses do not perform all of the characteristics of living things, though we may talk about them as being "alive". Viruses cannot grow. They do not require energy, use energy or release wastes, so viruses do not perform metabolic activities. They contain hereditary material (DNA or RNA) that is enclosed in a protein shell, but are not composed of cells. Viruses are also unable to respond to their environment. Though viruses can reproduce (in great numbers), they can only do so within a host cell.
Because viruses are not alive, they cannot be killed. Infections caused by viruses can be prevented by administering vaccines, which contain weakened forms of the virus itself. However, if you are unfortunate enough to contract a viral infection, treatment is tough. The symptoms of the infection can be treated (like taking a nasal decongestant to make your cold more tolerable), but medication will not take cure the disease and you will have to let your body fight it using your immune system. Certain viral infections can be fought by your immune system (like the flu and the cold), but others may be permanant and one may remain infected for life (like HIV, HPV and herpes). Whether a virus is easy to catch (like my cold!) or easily preventable (like HIV), our first defense against these infectious particles is our largest organ - our skin!
Important viral vocabulary words:
- host cell
- immune system
Infections caused by bacteria and viruses differ through one major concept - bacterial infections can be treated with antibiotics, whereas viral infections cannot be "cured" through medication. Some viral infections can be prevented through vaccination (like Measles-Mumps-Rubella, chicken pox, the flu, polio).
Tuesday, October 30th is a big day for us. On this day:
- Bacteriophage projects are due
- Bacteria/Virus test will be administered
- Notebooks will be collected
On Wednesday and Thursday, we will conclude this unit by viewing one of my favorite highly scientific films...."Outbreak". I've seen it a gazillion times (no exaggeration) and still love it!
Don't forget to check out the previous post on how a bacteriophage attacks its host cell.....I think that it is soooo cool!
Study hard and have a great weekend!
Wednesday, October 24, 2007
Monday, October 15, 2007
Comprised of just one cell, bacteria are the simplest of all living things. They can perform all of the functions necessary for life within their microscopic package.....reproduce, perform metabolic functions, grow and develop, respond to their environment and are made of (just one) cell. They can live in nearly any environment: in the oceans, on land, in your intestines, between your toes, in your food, and the list goes on and on! Members of the kingdom Archaea (which used to be classified with bacteria in the old kingdom Monera) are extremophiles , meaning that they can live in the planet's harshest climates (extreme cold as well as extreme heat). All life on Earth evolved from these amazing little guys....and the photosynthetic cyanaobacteria are even credited with introducing oxygen into our atmosphere (thus leading to further evolution of life on land).
Our vocabulary for the week includes:
- binary fission
Next week we will explore the wonderful world of viruses and learn why they are not considered organisms....fun stuff!
Wednesday, October 10, 2007
Scientists classify (or group/sort) living things according to the similarities that they share. Think about your science binder - it is set up for you to easily find certain work or put your work away. If I return a quiz to you, what section would you put it in? Your "Tests & Quizzes" section, of course! If I want to collect last night's homework assignment, it should take you 5 seconds to take it out of your "Classwork & Homework" section! Your work is classified according to what the assignment is, and the divider labels are your taxonomy!
A science example: plants contain a chemical called chlorophyll that they use to make their own food (it also makes them green). Every member of the plant kingdom shares this characteristic.
Each kingdom can then be broken into small groups, or phyla, of organisms that share even more similarities. Each phylum is divided even further into several classes; each class is divided into orders; each order is divided into families; families are divided into genera (sing. genus); and finally, each genus is divided is divided into many species.
The order of classification of the human is :
- Kingdom - Animalia
- Phylum - Chordata
- Class - Mammalia
- Order - Primates
- Family - Hominidae
- Genus - Homo
- Species - sapiens
Friday's quiz will require that you know the order of classification of living things (kingdom through species).
Monday, October 1, 2007
Our first test is scheduled for this Friday, October 5th. It will cover all of Chapter B-1, which includes:
- Natural selection
as well as
- The 5 characteristics of living things
It is very important for you to review the work that we have covered in the past two weeks, and to REVIEW YOUR VOCABULARY. Review work will be given in class on Thursday, and it is imperative that you complete it and use it to study from.
Please see me if you are unclear about anything that may be included on the test! :)