Biology: Levels of Organization, Characteristics of Life, Cell Types, and Body Systems

Levels of Organization

Cell → Tissue → Organ → Organ System → Organism

Cell

Smallest unit of life

Tissue

Group of similar cells working together (ex. muscle tissue)

Organ

Group of different tissues working together (ex. heart)

Characteristics of Life

Organization (Order), Growth and Development (Increase in size/maturity), Reproduction (= New organisms), Heredity (Pass on traits, w/ DNA), Response to stimuli (React to environment), Energy use/Metabolism (Obtain and energy use), Homeostasis (Internal stability), Evolution/Adaptation (Change over time)

Prokaryotic Cells

Simple cells, no nucleus, single circular chromosome in the nucleoid.

Eukaryotic Cells

Complex cells (Plants, Animals, Fungi, Protists), contain a nucleus and membrane-bound organelles

Circulatory System

Transports materials (oxygen, nutrients) and waste products thru the body

Nervous System

Body's control and coordination center, receives information (stimuli), processes it, and sends rapid electrical signals to initiate a response w/ muscle contraction

Respiratory System

Exchanges oxygen and carbon dioxide

Digestive System

Obtain nutrients & send them to the bloodstream

Homeostasis

Goal of most internal regulation, maintaining internal stability often involves counteracts to chance (ex. sweating to cool down)

Negative Feedback Loop (NFL)

Reverse the first change to return to the default point (ex. blood sugar drops = body releases glucagon = blood sugar rises back to normal)

Positive Feedback Loop

Amplifies the initial change (ex. contractions during childbirth)

Development Process

After fertilization → single-celled zygote divides w/ mitosis creating more identical cells

Differentiation

Mass of cells undergoes differentiation = cells become specialized (ex. muscle cells) to form tissues and organs