Ed Golson Outdoor Education

What is life?

Many people have tried to explain what life is, but there is no clear cut definition for what it is.  Life itself is really hard to define even though we know what is alive and isn't.  Despite not being able to define life, we can name general characteristics of living things.  Five common characteristics are:

1. Organization
2. Ability to make energy
3. Ability to reproduce
4. Respond to a stimuli
5. Ability to adapt

What does this mean?
The first characteristic of all living things is organization. This means that living things are organized from the smallest part to the largest, or on a hierarchy.  The hierarchy starts at the cell level, which is the smallest unit of life, and goes up to the whole entire organism.

The second characteristic of all living things is that they all have the ability to obtain and make energy.  Organisms either get energy through photosynthesis or through eating things that use photosynthesis.  Once the energy is in the organism, it converts the food energy into chemical energy to be used in the cells through metabolism.  Making energy in organisms is very important because without a constant supply of energy organisms would become disorganized and die.  To survive, organisms must be able to maintain homeostasis, or balance.

The third characteristic of living things that they have the ability to reproduce.  No matter what t ype of organism it is, it reproduces. Diff erent types of living things have different methods of reproduction.  For instance, most bacteria reproduce asexually, other organisms bud, some fungi produce spores, but most organisms including humans, animals, and few plants produce sexually.  Even sexually reproduction has variations, some organisms are hermaphrodites, meaning they contain both sexes within the organism and they can reproduce by themselves.  Most, however, have separate sexes which leads to the great genetic diversity on earth.  Reproduction is done through the process of mitosis, meiosis, or both.  Not only do all cellular forms of life reproduce, but they all have the ability to grow and develop.  Usually development is done in stages like metamorphosis in insects and amphibians. 


The fourth characteristic of living things is that they all respond to stimuli.  Responding to a stimuli is used in most organisms for safety purposes, for example many young children touch hot stoves and quickly move away from the heat, that is responding to a stimuli.  Plants also respond to stimuli, but not as rapidly as other organisms.  Usually their leaves will follow the sun to increase photosynthesis production and their roots will grow downward in order to reach water and minerals below earth's surface. 

The fifth characteristic of life is the ability to adapt.  The ability to adapt helps an organism survive in its environment. The more adaptable a species is, the more likely it will survive when the conditions around it change.  Natural selection occurs keeping the stronger individuals of the species alive which eventually makes the entire species theoretically more adapted to the environment.

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