Levels of Organization

5 Characteristics of Living Things All living things 1. are made of cells 2. use energy 3. grow and develop 4. respond to changes/stimuli 5. reproduce

cell-tissue-organ- organ system-organism smallest/first/least complex organ organism tissue organ system cell largest/last/most complex

cells the basic units of structure and function of all living things

tissue a group of related cells working together to perform a similar function

organ tissues that work together to perform a function

organ system a group of organs that work together to perform a specific function

organism a living thing

LEVEL ONE: CELLS Within a multicellular organism there is a division of labor.  Division of labor means that the work of keeping the organism alive is divided among the different parts of the body. 

LEVEL ONE: CELLS Each part has a specific job to do.  And as each part does its special job, it works in harmony with all the other parts. The arrangement of specialized parts within a living thing is sometimes referred to as levels of organization.  Cells, of course, are the first level of organization.

LEVEL TWO: TISSUES In any multicellular organism, cells rarely work alone.  Cells that are similar in structure and function are usually joined together to form tissues.  Tissues are the second level of organization.

LEVEL TWO: TISSUES Bone cells in your body form bone tissue, a strong solid tissue that gives you shape and support.  Blood cells in your body are part of blood tissue, a liquid tissue responsible for transporting food and oxygen throughout the body.

Connective tissue connects and supports parts of the body Connective tissue connects and supports parts of the body. Blood, fat, ligaments, cartilage, bones, and tendons are all connective tissues. Nerve tissue carries messages back and forth between the brain and every other part of the body. The brain, spinal cord, and nerves are made up of nerve tissue. Epithelial tissue covers and lines the surfaces of your body and organs, inside and out. They primarily serve as protective barriers. Skin is one example. Muscle tissue can contract, or shorten. Because of this, muscle tissue makes parts of your body move.

LEVEL THREE: ORGANS Tissues are further organized in organs, the third level of organization in living things.  Organs are groups of different tissues that work together. 

LEVEL THREE: ORGANS Your heart, for example, is an organ made up of muscle tissue, blood tissue, and nerve tissue.  You are probably familiar with the names of many of the body organs.  The brain, stomach, kidneys, and skin are some examples.

LEVEL FOUR: ORGAN SYSTEMS Like cells and tissues, organs seldom work alone.  They "cooperate" with one another and form specific organ systems.  Organ systems are the fourth level of organization in living things. 

LEVEL FOUR: ORGAN SYSTEMS An organ system is a group of organs working together to perform a specific function for the organism.

Level Four: Organ Systems Each organ in your body is part of an organ system, a group of organs that work together to perform a major function. For example, your heart is part of your circulatory system, which carries oxygen and other materials throughout your body. Besides the heart, blood vessels are organs that work in your circulatory system.

The nervous system detects and interprets information from the environment outside the body and from within the body; controls most body functions. The immune system fights disease. The excretory system removes wastes. The endocrine system controls many body processes by means of chemicals, like hormones.

The muscular system enables the body to move; moves food through the digestive system, and keeps the heart beating. The skeletal system supports and protects the body, and works with the muscular system to allow movement; makes and stores blood cells and stores some other materials.

The digestive system takes food into the body, breaks the food down into smaller particles, and absorbs the digested materials. The respiratory system takes oxygen into the body and eliminates carbon dioxide. The reproductive system produces sex cells that can unite with other sex cells to create offspring; controls male and female characteristics.

LEVEL FIVE : ORGANISMS You are an organism.  Dogs, trees, and sunflowers are also organisms.  Even a unicellular bacterium is an organism.  An organism is an entire living thing that carries out all the basic life functions.  The organism is the fifth level of organization.

LEVEL FIVE : ORGANISMS Cells, tissues, organs, organ systems, organisms--each level of organization interacts with every other level.  The smooth functioning of a complex organism is the result of all its various parts working together.