Unit 1: The basis of life                                              1   2   3   4   5   6

1. Characteristics of life

Living beings share some characteristics that allow us differentiate them from inert beings. These features are called characteristics of life. They are three:

   - Unit of composition.

       All living beings are made up by a short list of chemical elements which are
       especially abundant in them and very scarce in inert matter.

  - Unit of structure.

     All living beings are formed by cells. The simplest ones have only one cell

     and the most complex have millions of millions of cells.

          - Unicellular organisms. They are made up only by one cell that is self-sufficient.

          - Multicellular organisms. They are made up by more than one cell and they

            depend to each other.

     These cells are organized in levels of organisation with increasing structural

     complexity.

  - Unit of function.

    They perform the vital functions:

1.1. Answer these questions:

a. How can we classify matter from a chemical point of view?

b. What criteria have we followed to do it?

1.2. What vital function, nutrition (N), interaction (I) or reproduction (R) is performed

        in each case?

a. An oak tree loses its leaves in winter……………………………………………..

b. Flowers appear on a rosebush…………………………………………………….

c. A gazelle runs away from a lion……………………………………………………

d. A rabbit eats grass…………………………………………………………………..

e. An apple tree absorbs water through its roots……………………………………

f. A bacterium moves away from a dangerous substance………………………....