# Biology --- **Biology** is the study of life. For obvious reasons this is one of the subjects integral to [[nursing]]. Organisms stay alive by by maintaining **[[homeostasis]]**, or the balance of materials and [[biological energy|energy]] needed. Energy and materials come in the form of the four [[macromolecules]], proteins, carbohydrates, lipids, and nucleic acids. For smol biology, see [[microbiology]]. ## What Does It Mean To Be Alive? There are five fundamental characteristics that most biologists agree are essential for life. \# | Characteristic | Theory or Process ---|---------------- | ----------------- 1 | Organisms are made of cells... | [[cell#Cell Theory\|Cell Theory]] 2 | ...that come from existing cells | [[cell#Cell Theory\|Cell Theory]] 3 | Organisms aquire and use energy | [[Biological energy]] 4 | Organisms pass down information to their offspring | [[Inheritance\|Chromosome Theory of Inheritance]] 5 | Organisms evolve | [[evolution\|Theory of Evolution]] Above those fundamental characteristics, there are also traits that all living things exhibit: - Various levels of [[anatomy & physiology#Biological Organization|biological organization]] - The act of [[metabolism|metabolizing]] resources and energy - Growing (getting bigger) and developing (increasing in specialization of body parts and systems) - Responsiveness to outside/inside stimuli to maintain [[homeostasis]]. This can happen at all levels of organization - Regulating systems - [[reproduction|Reproduce]] ## Taxonomy, or the Domains of Life [[Taxonomy]] is the study of classifying organisms based on their similarities and differences. Most scientists agree that all living things fall under one of the three [[domains of life|domains]], bacteria, archaea, and eukarya. ## The Chemistry of Biology Biology is based in [[chemistry]]. Everything that can happen in biology can happen because of the physical properties of [[matter]], and how matter interacts with other matter. Of all the elements we know of, only 13 are really biologically important. Hydrogen, carbon, oxygen, nitrogen are particularly important, making up 99% of our body's mass. Another 0.85% of the body's mass are sulfur, potassium, sodium, chlorine and magnesium. These *love* making bonds with each other, and make all sorts of important molecular structures. ### Molecular Shape [[molecule|Molecular shape]] is a very important concept in biology, because without complementary shapes, molecule binding could not occur. Things have to fit *perfectly*. For example, the [[DNA|helix-turn-helix]] shape of DNA proteins. ### Organic vs Inorganic There are two main categories of molecules as they pertain to biology: organic and inorganic. **Organic** molecules contain *both* carbon *and* hydrogen (also known as containing a hydrocarbon). **Inorganic** molecules lack either carbon or hydrogen (or both). Take note that this definition classifies CO$_2$ as an *inorganic* molecul**e, despite it having carbon. ___