What are the requirements of life?

Nutrient and energy source Water Physical conditions which can sustain life

I. Introduction A. How do we tell what life is? 1. Dictionary a. “the quality that distinguishes a vital functioning being from a dead body” b. but what is that “quality” What Is Life?

2. Intuitive knowledge a. living things have complexity and ordered interaction among those complex parts b. much more difficult to describe or define life c. develop criteria for identifying life

B. Characteristics of life 1. Orderly structure or organization a. complex structure b. organic (carbon-based) molecules A

2. Acquire and use materials/energy a. maintain complexity b. maintain organization c. require energy - directly i. photosynthesis - indirectly i. energy stored in materials C

3. Maintain Internal Environment - Homeostasis a. organisms keep conditions in their bodies fairly constant to live b. metabolism in organisms is almost always constant c. conditions include temperature, water levels, salt levels A

4. Change during Lifetime a. development occurs during organisms lifetime - organized, replicated pattern of changes b. Growth - at sometime in lifecycle, all organisms become larger - conversion of acquired materials for increased size D

5. Reproduction a. Living things reproduce themselves b. Transmittal of genetic material (e.g. DNA) to new generation C

6. Respond to stimuli & Adjust to surroundings a. react to physical or chemical changes in their environment b. short term response - within single lifetime 7. Populations are modified & adapt to environment a. long-term response - requires multiple generations (usually many generations) b. requires modification due to genetic mutations c. Adaptation

Does it: 1) have orderly structure? 2) consume energy? 3) maintain internal environment? 4) develop or grow? 5) reproduce passing on heritable traits? 6) respond to stimuli 7) as a population, evolve to better “fit” the environment? IS IT ALIVE? Criteria for life