The Characteristics of Life Part 1: The Hierarchical Organization of Living Things *

WHAT IS LIFE? THE Question in Biology, but one we rarely take the time to consider. Why is this rock not alive?... …But this Rock Fungus is alive? Teacher Notes: there is a worksheet for the students to fill in – it focuses on the characteristics of life. ask students for some reasons why the rock is not alive. answers show the need for criteria to decide if something is alive or not. *

What is alive? *

COMMON Characteristics of Living Things Movement - ability to change the location of some or all of its parts Sensitivity - ability to respond to stimuli Development - orderly, progressive change in form (specialization)‏ Complexity - contains a large number of organized molecules & materials Death - ending of all processes, (or potential to perform processes), characteristic to living things *

Let’s try these characteristics out… FIRE - moves - responds - develops - dies - not very complex COMPUTER - responds - dies - complex - can’t move (debatable)‏ - can’t develop on its own (but can learn)‏ *

Thus these characteristics, although common to living things they are also seen in many non-living things, and thus are not enough to define life. Rock - not alive Rock Fungus - alive - moves some parts in response to stimuli - many different molecules, thus complex - can and does die - doesn’t move or respond - mostly silicon oxides thus simple - doesn’t die *

Fundamental Characteristics of life All living things… 1. Are Composed of Cells - Cells are the basic components of all living things. Some living things are uni-cellular, like bacteria, others are multi-cellular, like humans. *

2. Reproduce - All living things reproduce, by either asexual or sexual means. 3. Display Heredity - Living organisms inherit traits from the parent organisms that created them. *

4. Require Energy - Living things require energy, usually in the form of ATP. They use this energy to carry out energy-requiring activities such as metabolism and locomotion. 5. Respond to Stimuli - All living things respond to stimuli in their environment. *

6. Maintain Homeostasis - All living things maintain a state of internal balance. *

7. Evolve and Adapt - Living things adapt to their environment and evolve. *

For anything to be considered “alive” it must have ALL the Fundamental characteristics & at least SOME of the Common characteristics. Rock Fungus - alive Fire - not alive - consumes material & grows - can start new fires - doesn’t pass on traits - no cells - no stable internal environment - contains cells - produces new fungi - consumes material & grows - passes on traits to offspring - maintains internal environment *