biology

//**__BIOLOGY NOTES__**//
 * ===1C CELLS===

1. There are two primary types of cells. Eukaryotic and prokaryotic cells are the two main types of cells. Eukaryotic cells are called so because they have a true nucleus. Animals, plants, fungi and protists are examples of organisms that are composed of eukaryotic cells. Prokaryotes include bacteria and archaeans.
 * __Prokaryotic Cells__** **__Eukaryotic cells__**

 
 * ===1A OSMOSIS + DIFFUSION===
 * Osmosis is the movement of water through a cell membrane. The pressure that moves water in and out of cells is called water potential. Water moves from a region with high water potential to one with lower water potential. Pure water has a high water potential and so water is very likely to move into cells if they have water around them. Solutes lower water potential and so cells have a lower water potential than pure water. Plant cells take in water by osmosis until the cell wall pushes back on the cell's contents with the same pressure.
 *  Diffusion is passive. No energy is transferred for it to take place. Substances diffuse from a region of high concentration to a region of low concentration. This is called a concentration gradient. Rate of diffusion is affected by temperature because it affects the way that particles move. Rate of diffusion is affected by the surface area of membrane available. Diffusion can be facilitated by membrane proteins. The diffusion of water is called osmosis.
 * ** 2C MITOSIS **
 * The process in cell division by which the nucleus divides, typically consisting of four stages, prophase, metaphase, anaphase, and telophase, and normally resulting in two new nuclei, each of which contains a complete copy of the parental chromosomes. Also called // karyokinesis // .
 * **HUMAN CLONING**
 * Human cloning is the creation of a genetically identical copy of a human (not usually referring to monozygotic multiple births), human cell, or human tissue. The ethics of cloning is an extremely controversial issue. The term is generally used to refer to artificial human cloning; human clones in the form of identical twins are commonplace, with their cloning occurring during the natural process of reproduction. There are two commonly discussed types of human cloning: therapeutic cloning and reproductive cloning. Therapeutic cloning involves cloning cells from an adult for use in medicine and is an active area of research, while reproductive cloning would involve making cloned humans. Such reproductive cloning has not been performed and is illegal in many countries. A third type of cloning called replacement cloning is a theoretical possibility, and would be a combination of therapeutic and reproductive cloning. Replacement cloning would entail the replacement of an extensively damaged, failed, or failing body through cloning followed by whole or partial brain transplant.