Page 1 - 5. Response to stimuli, Species
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SAI International School
                                              Subject- Biology, Class-VI

                                        Topic-The Living and the Non-Living
                                      Subtopic- Response to Stimuli, Species
                                                     Lesson Notes

               Response to stimuli
                 •  Anything that triggers a reaction in an organism is called a stimulus.
                     (Plural-stimuli)
                 •  The reaction of the organism to the stimulus is called a response.
                 •  All living things respond to stimuli.
                 •  Non-living things do not show any response to stimuli.

                 •  We can perceive the changes in the environment or stimuli with the help of
                     our sense organs.(eyes, nose, tongue,ear,skin)



              Plants also respond to stimuli
                 •  Plants grow towards the source of light. The light is the stimulus and the
                     growth towards the light is called response. This property in plants is called
                     phototropism.

                 •  The roots of a plant grow in the direction of the Earth and the stem in the
                     direction opposite to the Earth. This property is called geotropism.

                 •  The Earth’s gravity is the stimulus and the respective growth of the stem and roots are
                     the responses.
                 •  Stems are positively phototropic but negatively geotropic while roots are
                     positively geotropic and negatively phototropic.

              Species

                 •  Species is a group of similar looking organisms that are capable of breeding
                     among themselves to produce young ones that can also reproduce.
                     Examples –
                 ❖       The German Shepherd is one species among the many species of dogs.
                 ❖       All humans form one species.



              WONDER BOX
                 •  Sir Jagadish Chandra Bose was the first Indian scientists who prove that plants are
                     sensitive to heat, cold, light, noise and various other external stimuli.









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