Levels of organization

Discuss human biological levels of organization from atom to organism.  Discuss each level in detail and describe how each contributes to homeostasis by giving specific examples.

          Biology is a life study that defines the difference between living versus nonliving organisms.  The world of living matter consists of levels of organization.  Each level is important in the function of human beings.  The levels are atom/molecule, cell, tissue, organ, organ systems and organism (Miller & Levine 13).

           All living organisms begin with an atom defined as a unit of matter.  To be considered matter it must contain the 4 characteristics of weight, volume, mass and density. An atom is microscopic in size, consisting of protons that have positive charges and neutrons with no charge which form the nucleus or center of the atom.  Outside the atom circulate a variety of electrons which help define the abilities of that atom.  Each atom, based on its structure, makes up different elements of matter.  A single atom or element can combine with other atoms to form a molecule.  Humans are made up of billions of atoms (Miller and Levine 28).  

         Even though each element begins in a pure state cooperative binding must occur for the building of a new structured matter.   Any disruption in the binding process or introduction of other elements, or an unstable environment can change the outcome.  For instance there is a presence of an atom of pure oxygen (an element required to be present for all living organisms that are aerobic in nature) in the environment.  Inject the pure element of carbon and the atoms will bind forming a strong triple co-valent bond and create a new compound called carbon monoxide, a totally different form of matter (Miller and Levine 31).  Carbon monoxide biologically can be the by-product of hemoglobin breakdown within the human body, but if found in large quantities can be a dangerous, toxic gas (Miller and Levine 800).  Take the same two atoms of carbon and oxygen and add one more oxygen atom to the compound and a new compound is formed called carbon dioxide.  Large quantities of carbon dioxide can drastically affect the homeostasis within a living body.   When the organism is balancing carbon dioxide correctly it is a natural by-product of respiration (Miller and Levine 799). 

         Some molecules are more stable than others but can join together to eventually form a single cell. All living organisms consist of the basic unit of life known as a cell. Cells are complete in nature but some living things remain in a unicellular state all of their life cycle while other organisms have more and more cells that become when combined as complex as the human body. The human body is the most complex form of life (Miller and Levine 160).

           Living organisms have several characteristics that make them common in nature and they must have these to be considered living.  These characteristics and functions are beginning with a basic unit cell, universal genetic code (heredity) ability, obtaining and using materials and energy, able to grow, develop and reproduce, respond to their environment, maintain a stable internal environment (homeostasis), and change overtime (evolution). Cells are generated from other pre-existing cell matter so the ability of reproduction is essential (Miller and Levine 160).    

         When considering the living species of human cells scientists classify these cells as eukaryotes.  To be able to have this classification the cell must have the three basic structures present; a plasma membrane, nucleus and cytoplasm. These structures contained within a single cell maintain its existence and survival.  The plasma membrane is the outside wall of the cell, the nucleus contains the genetic matter and communication, and the cytoplasm contains other structures that help the cell change food into energy.  The human cell works much like a sport team and each part has their own vital function, must communicate within, must send and contain receptors to receive messages through the effective use of chemicals. There are several stages that a cell goes through to multiple.  Each phase is critical, but DNA damage during division is the reason the cell cycle and cell death will occur because a homeostatic state has not been maintained to assure survival (Mader 164).

         When the cell does complete its phases and survives risk continues.  For example within the human body viruses can invade the body that contain proteins surrounding the cell wall that has the ability to bind to the protein receptors of the human cell allowing entry through the human cell wall.  In the HIV retroviruses the virus robs the human cell of its own genetic information by copying RNA to DNA and then replicates causing the virus to spread into the cells that specifically fight infection.  When this occurs homeostasis is disrupted within the human body and can lead to the drastic life threatening HIV (Miller and Levine 484). 

         The grouping together of cells forms human tissue and works in harmony to maintain homeostasis (Mader 607).  There are 4 primary tissue types in the human body; epithelial, connective, muscle and nerve (Mader 598).  Epithelial tissue lines organs and provides protection from abrasion and dehydration (Carpi).  Muscle tissue accomplishes hematopoietic tissue that manufactures blood cells helping the body maintain homeostasis with assistance in blood production.  Nerve tissue transmits impulses and provides physical support for the neural tissue, controls tissue fluids around the neurons, and helps defend the neurons from invading organisms (Carpi).

          Organs are the next level of organization in the body.  An organ is a structure that contains at least two different types of tissue working together for a common purpose (Carpi). There are many organs that perform as a system such as the heart, liver, kidneys, gastrointestinal, respiratory and even the skin, with the skin being the largest (Carpi).  There are three layers of the skin; the epidermis, dermis and subcutaneous.  The epidermis is the outermost layer of skin and works as a barrier between the outside environment and the inside of the body.  The dermis contains blood vessels that nourish skin cells and contains nerve tissue that provides blood supply, temperature, and sensations (Carpi).  The subcutaneous layer contains mostly connective and adipose tissue.  Adipose tissue known as fat helps cushion the skin and provides protection from the cold (Carpi).  Homeostasis for the body is maintained by protection, nerve impulses and circulation.  Homeostasis is disrupted anytime there is a break in the skin allowing potential for viral or bacterial invasion and body infection.

            Each organ and organ system must work together to maintain homeostasis.  The perfect balance of homeostasis does not permit the body to under work or overwork and each organ facilitates each other (Beers).  The nervous system is very complex and has the ability for the human body to survive, but it is dependent upon the ability to monitor internal and external conditions and making appropriate changes as needed.  A loss of homeostasis becomes evident in nervous system diseases such as Lou Gehrig Disease (Beers).  The heart and circulatory system move materials to and from body tissue very efficiently and loss of homeostasis occurs with coronary artery disease and disruption of blood supply (Beers). The digestive system takes in and digests food, and provides nutrient molecules that enter the blood and replace the nutrients that are being used by the body with the inability to eat causes death in the organism (Beers).  The respiratory system adds oxygen and removes carbon dioxide from the body and loss of homeostasis occurs anytime when ph imbalance occurs (Miller & Levine 799).  The liver and kidneys work together to maintain homeostasis by regulating blood glucose levels.  When the glucose enters the blood stream it is filtered out by the liver and stored as glycogen and then broken down at a later time as needed  by the secretion of insulin from the pancreas (Miller & Levine 39). The kidneys regulate the balance of water in the blood maintaining blood volume and blood pressure while excreting waste, salts and substances that regulate the PH of the blood to maintain homeostasis (Mader 695).

        Homeostasis is controlled somewhat by body hormones but it is ultimately controlled by the nervous system with the assistance from the brain by using negative feedback (Mader 608).    Negative feedback is a mechanism that maintains homeostasis and is regulated by a sensor and control center (Mader 608). The sensor detects imbalance in the internal body and the control center brings about change and when homeostasis has been restored the organ involved stops its’ action (Mader 608). Negative feedback works well for example with regulation of blood glucose and body temperature.

         Homeostasis is controlled as well with a positive feedback system.  This system is useful to maintain homeostasis in situations such as childbirth, blood clotting, and gastro intestinal breakdown of protein (Mader 609). A situation such as childbirth is a temporary change in the body’s environment.  Positive feedback is stimulated by the nerves, the brain, and pituitary gland to assist in the delivery process and eventual return to a pre-pregnant homeostatic state.

       The body can tolerate slight fluctuations within certain limits, but when homeostasis is outside the limits organ systems begin to work to re-regulate the situation.  Any lack of response by organs in a timely manner can cause long lasting effects on the body as a whole.  For example, when nutrients enter the body and glucose enters the blood stream, if the stimulation of insulin in the correct amounts does not occur it can give rise to a long lasting disease such as diabetes mellitus that can have very harmful effects on the body.  This disease is an example of the body’s struggle with maintaining homeostasis that will eventually affects every body system.
         “If life is to continue, temperature, moisture level, acidity and other physiological factors must remain within the tolerance range of the organism” (Mader 4). The miracle of survival of the organism is possible when homeostasis is maintained by body systems working together to routinely monitor internal conditions and make indicated adjustments without the conscious awareness of the organism.