Structure & Function in Biological Organization: Benefits & Disadvantages

Instructor: Joseph Said
This lesson will discuss biological organization in terms of cells, tissues, organs, and organ systems. It will also discuss the benefits and disadvantages of multicellular versus single-celled organisms.

Biological Organization

Biological life forms are composed of cells, which are the smallest unit of life, and then chemically can be broken down to molecules, which are different arrangements and combinations of atoms, the smallest particles which retain an element's identity. In a multi-cellular organism, these cells compose tissues, which compose organs, which compose organ systems, which ultimately form the entire organism. Different organisms all have the same basic biological structure, which starts with the cell. Single-celled organisms, while only being composed of a single cell, are still very complex in their intracellular workings. Multi-cellular organisms, such as ourselves, however, are much more complex and are composed of many different types of cells which all work together.

The Cell

Cells are the most basic unit of life and are composed of multiple cellular organelles. Think of organelles as the organs of the cell. Different organelles have different jobs, which all must tie in together for the cell to function properly. The nucleus is the library of the cell, and it holds all of the cell's information in the form of DNA. The Golgi apparatus is the cell's post office, and it ships proteins to the cell membrane and outside of the cell. The ribosomes are little protein-making factories, which are responsible for protein production. The lysosomes are the trash collectors of the cell and digest cellular garbage in little pockets of acid. The smooth endoplasmic reticulum is responsible for making lipids, which are used for cell membranes. The rough endoplasmic reticulum has ribosomes covering it, and makes proteins that are to be shipped out of the cell by the Golgi apparatus. The cell membrane and the nucleus, which is made of lipids as well, is very important for protection. Think of the cell membrane as a big wall that keeps out things that might hurt the cell and shouldn't be let inside. While all of these organelles and the cell work together to keep us all alive, there can be problems with this complex system when things like cancers form. Cancers, which are cells that don't know when to stop multiplying, pose a danger to multi-cellular organisms. Below is a picture of a typical animal cell with all of the organelles described above.


Organs and Organ Systems

Every organ in the body is a part of a larger organ system. For example, the heart, veins, arteries, and capillaries are all part of the cardiovascular system. The brain, spinal cord, and nerves are all part of the nervous system. Each of these organs and organ systems are made of special kinds of cells that make them unique. Heart cells don't look like brain cells, and vice versa. Every organ has unique cells that serve different purposes. It would not make sense for a heart cell and a liver cell to look exactly the same, as they have different jobs. Within organ systems, we also see different cell types. While the liver and the stomach are all part of the digestive system, we see that stomach cells are smooth muscle cells and liver cells are not. This makes sense, as the stomach has the job of holding food and the liver has the job of producing digestive acids and filtering toxins. Now while all of these cell types and organ system types look different, they all work together like the components of a car. The engine is completely different than the battery, which is different from the brake system, but they all must function and work together for the car to run properly. While this system works well in the human body most of the time, its interdependence on all organ systems working together is a pitfall. If one organ system fails, the entire organism may perish. Below is a picture of the human body displaying its various organ systems and also illustrating how they fit together in the body.

Organ Systems

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