BIOLOGY: Levels of Organization

1. MOLECULAR LEVEL - (smallest) molecules are made up of atoms e.g. dna atoms
2. CELL - basic unit of life e.g. blood cells, plant cells, brain cells
3. TISSUE - a group of cells that perform a specific function

Types of Tissues: Muscle Tissue - a group of cells that are specialized for contraction and movement -3 types of muscle tissues:

• Skeletal - voluntary, striated (legs, arms..)
  
• Cardiac - involuntary, striated (heart)
  
• Smooth - involuntary, unstriated (inner tissues)

Epithelial/Epithelium Tissue - a tissue that covers the body and its organs -secretes chemical substances (like sebum, perspiration) Connective Tissue - the tissue that binds together, supports and protects body structures - stores and transports materials -4 types of connective tissues:

• Bone tissue e. g. bones, tendons, ligaments
• Cartilage tissue e. g. cartilage (found in ears, nose)
• Adipose tissue e. g. fats
• Vascular tissue e. g. blood

Nervous Tissue - the tissue that carries information throughout the body -made of neuron (nerve cells)

axon - carries impulses away from the cell body - covered with schwann cells

dendrites - carries impulses away from the cell body (soma)

4. ORGANS - a group of tissues that work together to perform a common function

Organ Systems - made up of several organs working together to perform a function