This document discusses the different levels of biological organization from cells to biosphere. It begins by defining cells as the basic building blocks that make up all living things. Cells can work individually or together to form tissues, organs and organ systems. Finally, the highest level of organization is organisms, which are individual living things composed of organ systems that carry out life functions. The levels build upon each other, with cells forming tissues, tissues forming organs, and organs working together in organ systems to create a functioning organism.

1. Levels of Biological
Organization
This lesson will help you to understand and describe the different levels
of biological organization from cell to biosphere.

2. 1. CELL
• the simplest building blocks of life
• is the smallest independently functioning unit of a living
organism.
• can regulate its internal environment, take in and use energy,
respond to its environment, and develop and maintain its
complex organization.
• All organism is composed of cells. They occur singly in a great
variety of single-celled organisms or unicellular organisms like
amoebas and most bacteria
• Cells are the subunits that make up multicellular organisms such
as birds and trees. Your body consists of trillions of cells of many
different kinds.
• Cells that re similar in structure and functions are usually linked
together to form tissues.

3. 2. TISSUES
• are the second level of the biological organization.
• For example, the cells in our bones form bone
tissues, a strong solid tissue that gives us shape
and support. The blood cells in our body are part
of the blood tissue, a fluid tissue responsible for
transporting food and oxygen throughout our
body
• The tissues are further organized to form organs.

4. 3. ORGAN
• An organ is an anatomically distinct structure which
composed of two or more types of tissues that
work together.
• Our heart for example, is an organ that is made up
of muscle tissues and nerve tissues. You are
probably familiar with the names of several body
organs. We have the brain, lungs, stomach, kidneys
and the skin.
• Similar to cells and tissues, organs rarely work by
itself. Organs in a way “collaborate” with other
organs and perform a specific function. These
organs form an organ system.

5. 4. ORGAN SYSTEM
• The organ system is next higher level
of organization in living things.

6. 5. ORGANISM
• The best example of an organism is you.
Yes, you are an organism.
• Dogs, cats and other animals around us are
also organisms. Even single-celled
bacterium is an organism.
• Organism is an individual living thing that
may be made up of one or more organ
systems that carries out all the basic life
functions.

7. Study the illustration below. Cells, tissues, organs, organ systems and organisms comprises
the different levels of biological organization. The smooth functioning of a complex
organism happens when all these levels or parts work together.