Which term best describes an organism that can contain up to five levels of organization to carry out life functions?
Answers
Unicellular organisms are made of only one cell which performs all the function essential for the growth and multiplication of the organism. In multicellular organisms, however, there are different levels of organization which coordinate and work together for the proper functioning of the organism.
The human body has five levels of organization
Level 1: Cells
Cells are the basic units of life and form the first level of organization. Cells in the human body have specific functions. Examples include nerve cells, blood cells, liver cells, and so on. Cells themselves are made of various macromolecules that form organelles. Each organelle in a cell has a defined role, which makes a cell capable of delivering what it is designed to do.
Level 2: Tissues
A group of cells with similar structure and function is called a tissue. A tissue has a specific function which it accomplishes as a result of all its constituent cells working together. Examples for the tissues are cardiac, skeletal and smooth muscle tissue, epithelial tissue, blood tissue, nerve tissue, and so on.
Level 3: Organs
Two or more tissues organize to form organs, which serve a specific function. Examples are brain, heart, lungs, kidney, liver, and so on, each of which have definite functions. Most organs are made of all four types of tissue. The intestine, for example, is made of epithelial tissue as the inner lining, which helps in enzyme secretion and nutrient absorption. Epithelial tissue is covered by layers of muscle tissue, which help in peristaltic movements to move the food bolus. The intestine is also supplied by blood tissue (connective tissue) which helps in transporting nutrients absorbed by the intestine, and is connected to the brain through the nerve tissue, which conveys instructions from the brain.
Level 4: Organs system
A group of organs form the organ system, and together they perform a particular function. The heart and the blood vessels together make the cardiovascular system. Organs such as the nose, pharynx, trachea, lungs and the diaphragm work together as the respiratory system. The mouth, esophagus, stomach, duodenum, and the intestines together form the digestive system. Other examples of organ system include the endocrine system, integumentary system, muscular system, reproductive system, skeletal system, urinary system, immune system, etc.
Level 5: Organism
All the organ systems work together and carry out all life process in an organism. They can eat, excrete, grow, reproduce, and respond to environment.