Sunday, April 10, 2011

Levels of Organization

M Hanafi Said

In unicellular (single-celled) organisms, the single cell performs all life functions. It functions independently. However, multicellular (many celled) organisms have various levels of organization within them. Individual cells may perform specific functions and also work together for the good of the entire organism. The cells become dependent on one another.
Multicellular organisms have the following 5 levels of organization ranging from simplest to most complex:

Cell
a. Are the basic unit of structure and function in living things and  
 the smallest living units of structure and function are cells. 
b. May serve a specific function within the organism 
   Examples- blood cells, nerve cells, bone cells, etc.

Nerve Cells

Blood Cells

c.epithelial tissue - cover or line body surfaces; some are capable of producing secretions with specific functions.  the outer layer of the skin and sweat glands are examples of epithelial tissue. 
d. connective tissue - connects and supports parts of the body; some transport or store materials. blood, bone, and adipose tissue (fat) are examples
e.  muscle tissue - specialized for contraction, which brings about movement.  our skeleton muscles and the heart are examples
f. nerve tissue - specialized to generate and transmit electrochemical impulses that  regulate body functions.  the brain and optic nerves are examples.



Tissues
a. Made up of cells that are similar in structure and function and which work together to perform a specific activity
b. Examples - blood, nervous, bone, etc. Humans have 4 basic tissues: connective, epithelial, muscle, and nerve.

Organs
Made up of tissues that work together to perform a specific activity 
Examples - heart, brain, skin, etc.
Heart
Skin

 Lungs

Brain

Organ Systems
a. Groups of two or more tissues that work together to perform a specific function for the organism
b. Examples - circulatory system, nervous system, skeletal system, etc
c. The Human body has 11 organ systems - circulatory, digestive, endocrine, excretory (urinary), immune(lymphatic), integumentary, muscular, nervous, reproductive, respiratory, and skeletal.
circulatory
respiratory
digestive
endocrine
excretory (urinary)
 immune(lymphatic)
integumentary
 
muscular
 nervous

 reproductive
 respiratory
skeletal
Organisations
a. Entire living things that can carry out all basic life processes. Meaning they can take in materials, release energy from food, release wastes, grow, respond to the environment, and reproduce
b. Usually made up of organ systems, but an organism may be made up of only one cell   
such as bacteria or protist.
Examples - bacteria, amoeba, mushroom, sunflower, human 
                                                                                  
The levels of organization in the correct order then are:
cells -- tissues -- organs -- organ systems -- organism

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