Characteristics of Life!
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(1) Living things are made up of cells.
A cell is the smallest unit of an organism that is capable of all life functions.
The basic structure of cells is the same in all
organisms.
(2) Living things are based on a genetic code.
All organisms store the complex information they need to live,
grow, and reproduce in genetic code written in a molecule called
DNA. Molecules of DNA also determine an organism's traits. The passing of traits from parent to
child is called heredity.
(3) Living things maintain homeostasis (a stable internal environment).
Although conditions outside an organism may change dramatically, most organisms need to keep
conditions inside their bodies as constant as possible. This process is called homeostasis. An
organism unable to balance its internal conditions with its environmental conditions could
become ill and die.
(4) Living things reproduce.
All organisms reproduce which means that they produce new
organisms. Most plants and animals engage in sexual
reproduction, cells from two different parents unite to form the first
cell of the new organism. Other organisms reproduce using asexual
reproduction, in which a single parent produces offspring that are identical to itself. Because no
organism lives forever, reproduction is an essential part of living.
(5) Living things respond to their environment.
Organisms detect and respond to stimuli (singular: stimulus) from their environment. A stimulus
is a signal to which an organism responds. Organisms are dependent on one another and their
environment – that is, they are interdependent.
(6) Living things obtain and use materials and energy.
All organisms get energy to grow, develop, and reproduce. All of the
chemical reactions living things perform we need to get and use energy is
called metabolism. Without energy, life soon stops.
(7) Taken as a group, living things evolve.
The basic traits individual organisms inherit from their parents usually do not change. Over many
generations, however, given groups of organisms typically evolve, or change over long periods of
time. A species is a group of organisms that can produce more organisms. Individuals in a species
are similar, but not identical. Those individuals with genetic traits that better enable them to meet
nature's challenges tend to survive and reproduce in greater numbers, causing these favorable
traits to become more common.
DIRECTIONS: Answer the following questions about the reading IN COMPLETE SENTENCES.
1. What is the smallest unit of an organism that can be considered alive?
2. What is the molecule that stores the instructions for how a living thing works?
3. What is homeostasis?
4. Describe a situation when it is important that your body can maintain homeostasis.
5. Can a living thing survive without other living things? Explain your answer.
6. How many parents are required for sexual reproduction?
7. How many parents are required for asexual reproduction?
8. What is a stimulus?
9. Why do living things need metabolism?
10. What does evolve mean?