Exploring Life

What are the features of life?

       This article is about life  what It Is and how it is maintained. Life is something we may take for granted. Have you ever tried to explain what it means to be alive? Think about life characteristics as you read the following. Imagine that it's a hot summer day. You can't wait to get out of rut hot. stuffy house or apartment. With your dog. you head re to a nearby stream. At first, you practice slipping stones across the water, while the dog runs along the bank barking. Then you sit down on some sand on the bank under a large tree. Dragonflies skim over the water, and the noise of the insects and birds is all you can hear. The dog settles down on the bank under a tree and appears to fall asleep. It sure is great to be alive. But what does this mean? living things such as you and your dog and the tree are organisms. Organisms have certain features that rocks and water don't have. What makes you and your dog different from water and rocks?

   Organisms are made of one or more cells. You have some things in common with water and rocks in the stream because you are made up of chemicals as they are. However, if someone were to look at you or your dog or the tree under a microscope, it would be clear that each of you is made of units called Cells. Water and rocks are not. Cells are the smallest units of organisms that carry on the functions of life. 

Organisms move. If you ever watch a sleeping dog, it often looks lifeless. Then an ear twitches, or the dog may snore. What about plants? How do they move? 
    
  Organisms respond to changes in their environment. Does your dog come running every time it hears a can opener? Anything that an organism responds to, such as sound, is a stimulus. The reaction of an organism to a stimulus, in this case probably tail wagging and barking, is a response. What other kinds of stimuli can you think of?