Biology 48

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Organisms & Living Systems

The definition of life is controversial.

The current definition is that organisms are open systems that maintain homeostasis, are composed of cells, have a life cycle, undergo metabolism, can grow, adapt to their environment, respond to stimuli, reproduce and evolve.

Viruses are an example of a borderline case. For many years, science considered viruses as sort of “non-living poison.”

Life is a characteristic that distinguishes physical entities that do have biological processes from those things that do not. Examples of biological processes include signaling – and self-sustaining processes. Various forms of life exist, such as plants, animals, fungi, protists, archaea, and bacteria. The criteria can at times be ambiguous and may or may not define viruses, viroids, or potential synthetic life as “living”.

In the recent past, some scientists have proposed that a general living systems theory is required to explain the nature of life. Such a general theory would arise out of the ecological and biological sciences. The theory would attempt to map general principles for how all living systems work.


Day 1 – Introduction
Day 2 – Virtual Textbook

Instructor Resources

Standard Daily Material
  • Day 1 – Standard material – introduction day
  • Day 2 – Standard material – reading day
  • Day 3 – Standard material – make a presentation
  • Day 4 – Standard material – give a presentation
  • Extra! – Enrichment and remediation options
Other Topic Specific Resources

Special Notes and Notices

Instructor Emphasis:

  • Science & Engineering Practice: Develop and use models.
  • Cross-Cutting Concept: Stability and Change.

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