User:Atcovi/Science/Notes: Characteristics of Life and Levels of Organization


 * Abiotic Factors: Non-living factors in an ecosystem
 * Ex = Air, water, rocks, etc.


 * Biotic Factors: Living factors in an ecosystem
 * Ex = Humans, plants, insects, bacteria, etc.

Characteristics of Life

 * Characteristics of Life: The set of standards that scientists use to determine if something is living or non-living.
 * Characteristic 1: Living things are made up of units called cells.
 * Cells= Smallest unit of an organism that can be considered alive.
 * Cells can grow, respond to the environment, and reproduce.
 * Cells are complex and highly organized


 * Characteristic 2: Living things reproduce
 * Sexual reproduction (sex cells created through meiosis)
 * Asexual reproduction (cells divide through mitosis or fission)


 * Characteristic 3: Living things are based on a Universal Genetic Code
 * DNA


 * Characteristic 4: Living things grow and develop


 * Characteristic 5: Living things obtain and use materials and energy (metabolism)
 * Energy from sunlight (photosynthesis)
 * Energy from food


 * Characteristic 6: Living things respond to the environment
 * Organisms detect and respond to stimuli from their environment
 * A stimulus is a signal to which an organism responds. Two types of stimuli are:
 * 1) External stimuli (temperature, light)
 * 2) Internal stimuli (chemical signals)


 * Characteristic 7: Living things maintain a stable, internal environment
 * An organism's internal conditions (body temperature, water levels, etc.) must stay balanced in order to survive.
 * Homeostasis: Process organisms use to maintain an internal balance.


 * Characteristic 8: As a group, living things change over time = Evolution
 * Certain adaptations in a population will be favored in a given environment