All living things are made of cells and molecules that are organized into different levels. Cells are the basic units of life that make up tissues, organs, organ systems, and the overall organism. All cellular processes require energy and involve the movement and reactions of molecules like carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur. Homeostasis refers to the internal stability and balance maintained by involuntary processes within cells and between organ systems. Organs like the brain, heart, lungs, liver, stomach, intestines, and kidneys work together as specialized systems with unique shapes and functions to keep the human body living and healthy.

1. BIOLOGY
Unit 2 Notes:
Living
Organization

2. (1) Living Organization
• All living things are made of cells and
atoms/molecules.
• Levels of Organization:
– Atoms
– Cells (Basic units of life.)
– Tissues (Similar cells working on a common function.)
– Organs (Different tissues working on a common function.)
– Organ Systems
(Different organs working on a common function.)
– Organism (All organ systems maintaining homeostasis.)

4. (2) Cell Processes
• All living systems are made of atoms.
• All living things contain at least the following
biological elements:
Carbon, Hydrogen, Oxygen, Nitrogen,
Phosphorus, Sulfur
• All cellular processes are driven by energy
exchange and the movement and reacting of
different molecules.

7. (3) Homeostasis
• Involuntary processes and reactions are in place to
maintain Homeostasis within cells.
• Homeostasis = Internal stability / balance.

8. (4) Cell Specialization
• When cells are “specialized” this means that they
have a unique shape and a unique function.
• In our bodies we have many specialized cells,
which each complete a specific function, to
maintain overall homeostasis.

11. (5) Human Organs
• Humans have a lot of different organs to keep us
living and healthy.
• Some Main Internal Organs:
– Brain
– Heart
– Lungs
– Liver
– Stomach
– Small and Large Intestine
– Kidneys

12. (6) Organ Functions
• Brain: Controls all other organ systems and allows
us to respond.
• Heart: Pumps and circulates blood.
• Lungs: Bring in oxygen gas, and get rid of carbon
dioxide gas.
• Liver: Detoxifies chemicals and breaks down drugs
in blood.

13. Organ Functions Continued
• Stomach: Breaks down food into molecular
components.
• Small Intestine: Finish breaking down food and
absorb useful nutrients.
• Large Intestine: Absorb water, and excrete food
waste.
• Kidneys: Filter blood and maintain blood
homeostasis.