Biology Fall 2009--Rozema
Unit 1: Biochemistry Notes
from Tuesday 9-22-09
*Textbook pages16-22.
Characteristics of Life:
- When we refer to “living” things in this class, we are not comparing the dead and living. We are comparing systems/organisms which either currently are living, or at one time had the capability of living….. to systems which never had the capability of living.
- Living “things” = Biotic. Nonliving “things” = Abiotic (remember A- means without).
- The characteristics of life include:
(1) made of cells
(2) requires and manipulates energy and matter
(3) reproduces and passes on genetic info
(4) responds and adapts to stimuli/environment
(5) evolve
(6) excrete waste
(7) the ability to maintain balance/homeostasis
- “Made of Cells” à This means that all living things are made of at least one cell. Cells are the basic unit of life.
- “Requires and Manipulates Energy and Matter” à Where do you guys get your energy from? Food! What is food made of? Carbs, Fats, Protein…. Atoms and Molecules (Matter)! This means that something which is living needs a constant input of “food” or nourishment which can provide those atoms/molecules and energy. To be able to “manipulate” it means that the organism can break it down, do chemical reactions inside, and form other compounds it’s system can use.
- “Reproduces and Passes On Genetic Info” à This means that either sexually or asexually, the organism produces children and passes on part of their DNA code.
- “Responds and Adapts to Stimuli” à This means that when an organism’s environment changes (temperature, amount of food, amount of water), they recognize the change and determine how to survive.
- “Evolve” à This means that over time the population of organisms change to better suite their environment.
- “Excrete Waste” à This means that after the organism uses that food (energy and matter), their system/body can get rid of any waste products.
- “Ability to Maintain Balance / Homeostasis” à This is related to Responds + Adapts. Homeostasis = Balance.
Are Viruses Alive?
- In order to answer this question we need to see which of the “characteristics” viruses do not have.
- Before we begin that we need to understand what viruses are.
- Viruses are very complex systems. They are like parasites, meaning that they TAKE from other organisms so that they may benefit. Viruses cause the “common cold” and even the H1N1 Swine Flu.
- Viruses are extremely common, and there are tons of different viruses. All animals and even plants succumb to viruses.
- Are Viruses Made of Cells? This is a difficult question to answer w/o considering the other characteristics. Let’s leave this until the end.
- Do viruses require energy and matter? Well… they require the cells of plants, animals and bacteria. In this sense they are using the energy and matter of other organisms to survive, so Yes.
- Do viruses reproduce and pass on genetic info? Yes! They store their genetic info on the very inside, like a cell nucleus. They reproduce by infecting other cells. They land on a cell, and inject their RNA into the cell. That poor, innocent cell, then begins making the parts of the virus as if it were its own genes. You can kind of think of the cell like a zombie now. It is possessed, and completely taken over by the virus.
- Do viruses respond and adapt to stimuli? No! Viruses have no means of altering their behavior in order to survive. They in fact have no behavior. If they are not in fluid or capsules, they dry up and are no longer viable!
- Do viruses evolve? Yes! First viral RNA mutates extremely frequently and rapidly. These mutations, or changes in its genes, lead to the production of new populations of viruses. Second, if 2 different viruses infect the same cell at the same time, the cell will begin producing a hybrid of the two, and thus a new population! (This is where H1N1 came from!)
- Do viruses excrete waste? No! They don’t really eat or breathe….. do you guys think we should reconsider our answer for energy and matter?
- Do viruses maintain homeostasis? No! Again they don’t really respond to anything.
- After that do you guys agree viruses are NOT alive? ….Because they are NOT alive. While they have many characteristics cells do, and are complex like living organisms, they are not actually living.