ETV “Junior Secondary Science” Programme

Sense Organs

Teachers’ Notes

Target Audience

Secondary 1 - 3

Duration

20 minutes

Production Aim

This programme is a teaching resource produced especially for enriching the classroom teaching in S2 level of the Syllabus for Science (Secondary 1 – 3) prepared by the Curriculum Development Council (1998).

The content of the programme serves to illustrate the following parts of the Syllabus：

Unit 11 Sensing the Environment

Topic 11.3 – Limitations of our eyes :‘Blind spot’, Topic 11.4–Defects of the eye : ‘Colour blindness’, andTopic 11.8–Senses of smell, taste & touch : All Key Points and most parts of Content.*

[Limited by the length of the programme, ‘Our sense of smell affects our sense of taste’ and ‘Our skin is not reliable in detecting hot and cold’of the Core Content in Topic 11.8 will be dealt with in another programme ‘The Brain and the Senses’.]

Key Points

  1. An introduction to irritabilityin animals and plants.
  2. An introduction to the structure and function of the sense organs for sight, hearing, balance, smelland taste in our body.

Content Outline

This programme is divisible into 7segments as follows:

  1. Sense

The film uses a mimosa plant, a grasshopper, a bird and a fish to illustrate irritability in animals and plants.

  1. Sensing the Environment

Using an African snail as the object, the film shows a series of simple experiments to demonstrate that organisms can detect and respond to stimuli in their environment.

  1. Our Eyesight

(i)With the help of computer graphics, the film shows the structure of the human eye and the formation of image; structure and function of the retina are also presented.

(ii)The film shows the characteristics of colour blindness by analyzing the relationship between the cone cells and the sense of colour;method of testing for colour blindness is also shown. The programme also points out that colour blindness is a kind of hereditary defect.

(iii)The film uses simple experiments to illustrate stereoscopic vision, and the formation of stereoscopic images.

(iv)The film uses simple experiments and a rearview mirror in a car to demonstrate the blind spot effect. An optometrist from the Hong KongPolytechnicUniversity shows how to make observation on the human retina. The blind spot inside our eye is shown by technique of computer recording.The formation of the blind spot effect is also explained as well.

  1. Double Function of the Ear

(i)The film shows the structure of the human ear including external ear, middle ear and inner ear with the help of model and graphics. The mechanism of the formation of the sense of hearing is also shown.

(ii)The film emphasizes that our ear is the organ for both the sense of hearing and the sense of balance; it also mentions that the semi-circular canals and the vestibule in the inner ear are the actual structures for the sense of balance.

(iii)Computer graphics are used to explain the function of the semi-circular canals and the vestibule as the organs for sensing balance; the reason for car- or sea-sickness is also explained.

  1. Nose and Smell

(i)The film uses simple experiments to show that our nose has the ability to sense different smells.

(ii)Model and computer graphics are used to explain the mechanism of the sense of smell.

  1. Tongue and Taste

(i)The film uses simple experiments to show that our tongue has the ability to sense different tastes.

(ii)Computer graphics are used to explain the mechanism of the sense of taste; and to show the distribution of zones for sensing different tastes on our tongue.

  1. Skin and Touch

(i)The film uses simple experiments to show that our skin has the abilities to sense temperature and touch.

(ii)Computer graphics are used to show the structure of the skin, as well as the different receptors for temperature, touch, pressure and pain.

(iii)Simple experiments are used to show that our finger tips and the skin on our shoulders have different degrees of sensitivity; computer graphics are then used to explain the reason.

Suggestions for Utilization

  1. The entire programme may be shown to the students in one session to serve as a way of consolidation after the teaching of the topic ‘Sensing the Environment’.
  2. The programme can also be shown in four sections: segments 1 and 2 to motivate students before teaching unit 11;segment3 as an extension to “The Eye”, another programme in this series, to help explaining the structure of the retina,the principles ofcolour vision, colour blindness, stereoscopic vision and blind spot effect; segment 4as an extension to “Sound and the Ear”, still another programme in this series, to let the students grasp more fully the structure and function of the ear; and segments 5 to 7 to help teaching the senses of smell, taste and touch in human.
  3. The programme can also be shown in a S4/5 Biology/Human Biology lesson as a starting point of the lesson, or as a way to motivate students.
  4. Teachers may spend 5 to 10 minutes before the show to lead a discussion with students. After the show, teachers may spend another 10 to 15 minutes discussing with students in order to consolidate the concepts and principles illustrated in the programme. Teachersare advised to refer to theSuggested Activities listed below.

Suggested Activities

(The following activities are suggested for teachers’ reference only. Teachers may wish to select suitable activities according to students’ abilities, the learning environment of the class, and the teaching time available.)

Preparation before viewing the programme

Starting from sight and hearing and extending to smell, taste and touch, teachers may lead students to discuss how organisms in general, and human beings in particular, detect changes in the environment. Teachers may then help students to grasp the concept of a ‘sense organ’, including eye, ear, tongue, nose and skin. Teachers need not elaborate too much, but ask the students to concentrate on the programme.

Activities after viewing the programme

  1. Teachers may ask the students to repeat the experiments of ‘touching the tip of the pencil’ and ‘finding the blind spot’ as shown in the programme.
  2. Teachers may ask the students to repeat the experiments at home of finding the areas most sensitive to the tastes of sweet, salty, bitter and sour in the tongue. Sugar solution, salt solution, lemon juice and bitter gourd juice could be used in tasting. Teachers may ask the students to find out which area of the tongue is most sensitive to each of the different tastes, and draw a picture to show the distribution of these areas on the tongue.
  3. Teachers may discuss with the students why the finger tips and the palm of our hands are more sensitive than the back of the hands.

(Hint : Why we often use our fingers and the palm of our hands to handle tools and objects, and to sense the texture of things?)

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