Page 110 - Science Class 07
P. 110

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              Excretion in Human Beings and



                                                                                           Animals




               •  Different Types of Wastes and Their Excre on           •  Excretory System in Human Beings
               •  The Process of Excre on in Human Beings               •  Malfunc on of the Excretory System
               •  Dialysis                                              •  Excre on in   Other  Animals

              In  the  previous  chapters,  you  have  studied      living  beings.  However,  the  way  of  excere on
              about  nutri on,  i.e.,  diges on  and  respira on    may vary from organism-to-organism.

              that  deals  with  intake,  diges on,  absorp on         DIFFERENT TYPES OF WASTES AND THEIR
              and eges on of the food that is eaten. It is not                         EXCRETION
              difficult to know that the food we eat and the
                                                                    We eat different kinds of food and drink various
              water  we  drink  leave  their  waste  parts  inside   kinds of liquids. These food materials a er use
              the body. The food a er being digested, leaves        convert into solid as well as liquid wastes. The
              solid  waste  that  we  call  stool.  The  water  that   O   we  breathe  in  is  converted  into  CO   a er
                                                                     2                                         2
              goes in to the body leaves some liquid wastes.        relasing  energy  from  the  food  during  the
              Some of it gets out of the body in the form of        process of respira on.
              sweat  and  the  rest  as  urine.  Moreover,
                                                                    Let’s see how these waste products are thrown
              respira on  yields  carbon  dioxide  which  is  a     out from our body:

              waste product too.
                                                                    Cellulose and Other Solid Wastes
              As  none  of  these  waste  materials  is  useful  to
                                                                    The  food  that  we  eat  contain  cellulose  and
              the  body,  they  have  to  be  thrown  out  of  it
                                                                    other nutrients. By the process of metabolism
              regularly. They are excreted by different organs
                                                                    food  breaks  down  into  simpler  substances.
              of the body. This process is also a life-process      Energy  and  other  nutrients  extracted  is
              because  if  these  materials  are  not  excreted,    metabolism,  are  absorbed  by  our  body.
              they will surely make the body ill.                   Cellulose  is  an  undiges ble  substance  which

              So, we can define excre on as follows:                 remains  in  solid  form  in  our  body.  Besides,
                                                                    many  other  components  of  food  remain
              Excre on is the life-process of removing solid,
                                                                    undigested. This undigested food gets collected
              liquid and gaseous wastes from the body. The
                                                                    in  large  intes ne  and  comes  out  of  the  body
              process  of  excre on  is  common  in  almost  all    through anus. This process is called eges on.

               110                                                                                          Science-7
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