How do scientists determine if something is a living creature?

  1. Homeostasis: Regulation of the internal environment to maintain a constant state; for example, electrolyte concentration or sweating to reduce temperature.
  2. Organization: Being structurally composed of one or more cells, which are the basic units of life.
  3. Metabolism: Transformation of energy by converting chemicals and energy into cellular components (anabolism) and decomposing organic matter (catabolism). Living things require energy to maintain internal organization (homeostasis) and to produce the other phenomena associated with life.
  4. Growth: Maintenance of a higher rate of anabolism than catabolism. A growing organism increases in size in all of its parts, rather than simply accumulating matter.
  5. Adaptation: The ability to change over a period of time in response to the environment. This ability is fundamental to the process of evolution and is determined by the organism's heredity as well as the composition of metabolized substances, and external factors present.
  6. Response to stimuli: A response can take many forms, from the contraction of a unicellular organism to external chemicals, to complex reactions involving all the senses of multicellular organisms. A response is often expressed by motion, for example, the leaves of a plant turning toward the sun (phototropism) and by chemotaxis.
  7. Reproduction: The ability to produce new individual organisms, either asexually from a single parent organism, or sexually from two parent organisms.
    Taken from Wikipedia

To Be Completed:
What is a cell?
Fundamental structural unit of all life. The cell consists primarily of an outer plasma membrane, which separates it from the environment; the genetic material (DNA), which encodes heritable information for the maintainance of life; and the cytoplasm, a heterogeneous assemblage of ions, molecules, and fluid.
Types of cells
Cell structure and function
Asexual vs. Sexual Reproduction
Building Blocks (Cells + Cells = Tissues, Tissues + Tissues = Organs, Organs + Organs = Organ Systems)

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