Levels of Organization (anatomy)

The Levels of Organization is a term used in basic biology, anatomy, and physiology. It is used with five basic concepts, the smallest the cell. Many specialized cells make up a tissue, many tissues an organ, many organs an organ system, and finally, many organ systems an organism. In bizarre cases microorganisms (unicellular) and superorganisms, only one cell or many organisms may occur within a single species.

Level I: Cells

The cell is the smallest unit known that can perform all the life processes and the smallest level of organization. Almost all cells (prokaryotic and eukaryotic) have a covering called a cell membrane which may be covered by a cell wall, a "nucleus" or brain with genetic material, a cytoplasm of cytosol, a cytoskeleton, and organelles- whether membrane-bound or not. Cells differ drastically between organisms and between kingdoms- almost no cell is even close to being the same. A list of common organelles is listed below:
*Mitochondria
*Chloroplasts
*Ribosomes
*Endoplasmic Reticulum (includes smooth ER)
*Vacuole
*Nuclei (includes nucleolus)
*Peroxisome
*VentriclesOther less common or varying structures are listed in the main|Organelles

Level II: Tissues

A tissue is a collection of specialized cells that perform a specific function. The four types of tissues are muscle tissues, nervous tissue, epithelial tissue, and connective tissue. When all these tissue join together they form an organ

Level III: Organs

An organ is a group of tissues that perform a specific function or groups of functions. Animal organs include the brain, the lungs, the liver, and the stomach and some plant organs are leafs, roots, and the stem. Your senses are also organs- your ears, tongue, eyes, nose, and skin are sensory organs. Organs inside an animals body are often called internal organs or more scientifically viscera (pl. viscus). Plant organs are split into both vegetative (root, stem, etc.) and reproductive organs (flower, seed, etc.). A list of human organs is provided below in alphabetical order:
*Arteries
*Bronchi
*Heart
*Lungs
*Muscles
*Skin
*Tongue

Level IV: Organ Systems

An organ system is a collection of organs that perform a specific function- the circulatory system or digestive system for example. Several organ systems are present in humans and other creatures have different kinds of systems. Plants have vascular systems and sharks have a kind of "electromagnetic system". An organ system cannot live by itself and is dependent on other organ systems to form an organism. Here is a list of human organ systems and the organs they are made up of:
*Circulatory System: the heart, blood, and blood vessels
*Digestive System: the salivary glands, esophagus, stomach, liver, gallbladder, pancreas, intestines, rectum, and anus
*Endocrine System: the hypothalamus, pituitary gland, pineal body, thyroid, parathyroids, and adrenals
*Integumentary System: the skin, hair, and nails
*Lymphatic System: the leukocytes, tonsils, adenoids, thymus, and spleen
*Muscular System: the muscles
*Nervous System: the nerves, brain, spinal cord, and peripheral nerves
*Reproductive System: the ovaries, fallopian tubes, uterus, vagina, mammary glands, testes, vas deferens, seminal vesicles, prostate, and penis
*Respiratory System: the pharynx, larynx, trachea, bronchi, lungs, and diaphragm
*Skeletal System: the bones, cartilage, ligaments, and tendons
*Uninary System: the kidneys, ureters, bladder, and urethraOrgan systems may be closely intertwined and called things like the muscoskeletal system or neuroendocrine system.

Level V: Organisms

An organism is made up of cells and are either unicellular or multicellular. The fifth level of organization is referring to multicellular organisms. Organism is also the largest level of organization "known"- it is highly likely that superorganism will be excepted as the sixth level of organization. An organism is a type of living thing that is made of cells and is close enough- "genetically"- to be considered a species. Millions of organisms are currently known, from "Paramecium" to ourselves. All generally known or excepted organisms fit into six kingdoms or regnums: Animalia (animals), Plantae (plants), Protista (protists), Fungi (fungi), Archaea (or Archaebacteria), and Bacteria. Viruses and subviral agents are not generally considered organisms. Scientists are currently looking into the creation of artificial life and cybornetics and may end up looking towards the levels of organization for guidance and research.

References

*Haircourt Science Textbook 2007 Edition