- The Cells: The cell is the basic unit of life. It is the fundamental unit of structure and function of life. It may perform a specific function in the body of a living organism. Examples of cells are- blood cells, nerve cells, bone cells, etc.
Cells are made up of organelles which take care of everything starting from housing the cell’s DNA, to the manufacture of energy. Processes that take place inside the body are carried out on a cellular level.
For instance during the movement of the leg, it is the function of the nerve cells to transmit this signal from your brain to the muscle cells in your leg.
- Tissues: The tissue is composed of cells that have similar structure and function and which work together to carry out a particular function. Examples of tissues are blood, nervous, bone, etc.
Human beings have 4 fundamental tissues: connective tissue, epithelial tissue, muscle tissue, and nerve tissue. Animal tissue can be subdivided into 4: epithelial tissue, connective tissue, muscle tissue, and nervous tissue.
- Organs: Organs are composed of tissues that work together to perform a specific function. Examples of organs are the heart, brain, skin and so on. For instance, the brain is made up of a lot of different types of tissues which include the nervous and connective tissues.
- Systems: The system is a group of tissues to work together to achieve a particular function in an organism. Examples of systems are the circulatory system, nervous system, skeletal system, etc.
The Human body is made up of 11 systems which include- circulatory, digestive, endocrine, excretory or urinary, immune or lymphatic, integumentary, muscular, nervous, reproductive, respiratory, and skeletal system.
All these systems work together to keep the body functioning optimally. For example nutrients gotten through the digestive system are transported throughout the body by the circulatory system. In the same way, the circulatory system circulates the oxygen that is assimilated by the respiratory system.
- Organisms: This is the entire living things that can perform all basic life processes. This means that such living thing can take in materials, discharge energy from food, free wastes, grow, respond to the stimuli in the surroundings, and reproduce.
The are normally made up of systems which combine together to form the organism but an organism can as well be composed of only a single cell like in the case of bacteria or protists such as bacteria, amoeba, mushroom, sunflower.
Living organisms are extremely ordered and possesses the ability to grow, develop, and reproduce. Multi-cellular organisms in addition to human beings depend on the collaboration between organs, tissues, cells, and system to exist.
The levels of organization of life in the right order is therefore
cells – tissues – organs – organ systems – organisms.
The pyramid of life is a hierarchical structure for the organization of life.