Lesson Note on Sense Organs: Smell, Taste, Touch and Hearing for SSS 2

Class: Senior Secondary School 2 (SS2 / SSS2)
Term: 3rd Term
Week: 7
Age: 16 years
Duration: 45 minutes
Subject: Biology
Curriculum Theme: Physiology of Living Organisms
Previous Lesson: Neurons: Types, Impulses and Reflex Actions.
Topic: SENSE ORGANS
Subject Matter: Organ of smell and mechanism of smelling with olfactory chemoreceptor, adaptation for survival dog sniff during hunting and chemoreceptors in insects and antenna sensing, taste buds on tongue and role in testing, sensory nerve endings receptors for touch pressure heat and pain, structure of the ear and part played by the various parts

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:

• Define sense organs.
• Identify the organs of smell, taste, touch, and hearing.
• Describe the mechanism of smelling and tasting.
• Explain the role of different parts of the ear.

Affective Domain:

• Appreciate the importance of sense organs for survival.
• Value the proper care and maintenance of sense organs.

Psychomotor Domain:

• Draw and label the main parts of the human ear.
• Identify areas of the tongue sensitive to different tastes.

Social Domain:

• Discuss adaptations of sense organs in other animals, such as dogs and insects.

Reference Materials

The following resources were used in planning this lesson:

• Senior Secondary Schools Education Curriculum
• State Unified Scheme of Work
• Modern Biology for Senior Secondary Schools by S.T. Ramalingam
• https://www.biologyonline.com/tutorials/sense-organs
• https://www.khanacademy.org/science/biology/human-biology/sensory-systems

Instructional Materials

The teacher will teach this lesson with the aid of:

• Textbook
• Posters showing the human sense organs (nose, tongue, skin, ear)
• Chart of the human ear
• Samples of substances with distinct smells (e.g., perfume, onion)
• Samples of substances with distinct tastes (e.g., sugar, bitter leaf)

Rationale for the Lesson

This lesson helps pupils understand how their bodies perceive the world around them through various sense organs. It enables them to appreciate the complex mechanisms involved in smelling, tasting, touching, and hearing, which are essential for their daily interactions and survival.

Prerequisite/Previous Knowledge

Pupils should have prior knowledge of the basic structure of the human body and the concept of receptors from their previous biology lessons.

Lesson Content/Board Summary

SENSE ORGANS

Sense organs are specialized organs that contain receptors for specific stimuli, enabling an organism to perceive its environment.

The Organ of Smell (Nose)

The nose is the primary organ for smell. It contains olfactory chemoreceptors located in the olfactory epithelium at the roof of the nasal cavity.

• Mechanism of Smelling: Odorant molecules in the air dissolve in the mucus layer of the olfactory epithelium and bind to specific receptors on the olfactory receptor cells. This triggers nerve impulses that are sent to the brain for interpretation as a particular smell.
• Olfactory Chemoreceptors: These are specialized nerve cells that detect chemical stimuli (odorants).
• Adaptation for Survival:
  • Dogs: Possess a highly developed sense of smell due to a large number of olfactory receptors, crucial for hunting, tracking, and detecting substances.
  • Insects: Use antennae as chemoreceptors to detect pheromones, food sources, and other chemical signals in their environment.

The Organ of Taste (Tongue)

The tongue is the primary organ for taste. It is covered with tiny bumps called papillae, many of which contain taste buds.

• Taste Buds: These are clusters of sensory cells that detect chemical stimuli (tastants) dissolved in saliva.
• Role in Tasting: Tastants bind to receptors on taste cells within the taste buds, generating nerve impulses sent to the brain for taste perception.
• Areas of the Tongue Sensitive to Taste:
  • Sweet: Primarily detected at the tip of the tongue.
  • Sour: Detected at the sides of the tongue.
  • Salty: Detected at the front sides of the tongue.
  • Bitter: Detected at the back of the tongue.
  • Umami (savoury): Detected across the tongue.

The Organ of Touch (Skin)

The skin is the largest sense organ, containing various sensory nerve endings or receptors that detect different stimuli.

• Sensory Nerve Endings/Receptors:
  • Touch Receptors (e.g., Meissner’s corpuscles): Detect light touch and texture.
  • Pressure Receptors (e.g., Pacinian corpuscles): Detect deep pressure and vibrations.
  • Heat Receptors (Thermoreceptors): Detect warmth.
  • Cold Receptors (Thermoreceptors): Detect cold.
  • Pain Receptors (Nociceptors): Detect damaging stimuli that cause pain.

The Organ of Hearing (Ear)

The ear is responsible for hearing and balance. It is divided into three main parts:

• Structure of the Ear:
  • Outer Ear: Consists of the pinna (auricle) and the external auditory canal (ear canal).
  • Middle Ear: An air-filled cavity containing the tympanic membrane (eardrum) and three ossicles (malleus, incus, stapes). It connects to the pharynx via the Eustachian tube.
  • Inner Ear: Contains the cochlea (for hearing) and the semicircular canals and vestibule (for balance).
• Parts Played by the Various Parts:
  • Pinna: Collects sound waves.
  • External Auditory Canal: Channels sound waves to the eardrum.
  • Tympanic Membrane (Eardrum): Vibrates when hit by sound waves.
  • Ossicles (Malleus, Incus, Stapes): Amplify and transmit vibrations from the eardrum to the oval window of the inner ear.
  • Eustachian Tube: Equalizes pressure between the middle ear and the outside atmosphere.
  • Cochlea: Converts sound vibrations into nerve impulses that are sent to the brain.
  • Semicircular Canals and Vestibule: Detect head movements and maintain balance.

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher asks pupils to carefully smell a safe, controlled scent (e.g., perfume or a specific food item) and describe their perception. The teacher then guides pupils to discuss the different tastes they know and which parts of the tongue are sensitive to sweetness and bitterness.
Pupils’ Activity: Pupils smell the scent and describe what they perceive. They participate in the discussion about tastes and identify tongue areas.
Learning Point: Pupils are introduced to the concept of senses and their importance.

Step 2: The Organ of Smell (Nose)

Time: 7 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher explains the structure of the nose, focusing on the olfactory chemoreceptors and the mechanism of smelling. The teacher also discusses adaptations for survival, giving examples of dog sniffing during hunting and chemoreceptors in insect antennae.
Pupils’ Activity: Pupils listen attentively, ask questions, and take notes.
Learning Point: Pupils understand how the nose functions as an organ of smell and its adaptations.

Step 3: The Organ of Taste (Tongue)

Time: 7 minutes
Teaching Skill: Explanation/Discussion
Teacher’s Activity: The teacher explains the structure of the tongue, the role of taste buds, and the specific areas of the tongue sensitive to different tastes (sweetness, bitterness, sourness, saltiness, umami).
Pupils’ Activity: Pupils listen, observe diagrams, and note down the different taste areas on the tongue.
Learning Point: Pupils learn about the tongue as an organ of taste and the distribution of taste perception.

Step 4: The Organ of Touch (Skin)

Time: 5 minutes
Teaching Skill: Explanation
Teacher’s Activity: The teacher discusses the skin as a sense organ and introduces the various sensory nerve endings responsible for detecting touch, pressure, heat, cold, and pain.
Pupils’ Activity: Pupils listen and understand the different types of receptors in the skin.
Learning Point: Pupils identify the skin as the organ of touch and its diverse receptors.

Step 5: The Organ of Hearing (Ear) – Structure

Time: 7 minutes
Teaching Skill: Visual Aid/Explanation
Teacher’s Activity: The teacher displays a chart of the human ear and identifies the outer, middle, and inner ear, guiding pupils to observe the main structures.
Pupils’ Activity: Pupils observe the chart, identify the parts, and begin to sketch the ear.
Learning Point: Pupils learn the overall structure of the human ear.

Step 6: The Organ of Hearing (Ear) – Functions

Time: 7 minutes
Teaching Skill: Explanation/Questioning
Teacher’s Activity: The teacher explains the specific role and function of each part of the ear (pinna, ear canal, eardrum, ossicles, Eustachian tube, cochlea, semicircular canals, vestibule) in hearing and balance.
Pupils’ Activity: Pupils listen, ask questions, and complete their ear diagrams with labels and functions.
Learning Point: Pupils understand the functions of different parts of the ear.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

1. Define sense organs.
2. Name three sense organs and their corresponding stimuli.
3. Describe the role of olfactory chemoreceptors in smelling.
4. List the five basic tastes and identify the tongue areas sensitive to sweetness and bitterness.
5. Draw and label the main parts of the human ear.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 2 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the lesson by reiterating the importance of sense organs for perceiving the environment and maintaining survival. The teacher assigns homework: research common disorders of the sense organs.
Pupils’ Activity: Pupils listen to the summary and copy down the homework.
Learning Point: Pupils reinforce their understanding of sense organs.

Lesson Keywords

• Sense Organs – Specialized organs containing receptors for specific stimuli.
• Olfactory Chemoreceptors – Receptors in the nose responsible for detecting smell.
• Taste Buds – Clusters of sensory cells on the tongue that detect taste.
• Sensory Nerve Endings – Receptors in the skin that detect touch, pressure, heat, and pain.
• Cochlea – Part of the inner ear responsible for hearing.
• Tympanic Membrane – The eardrum, which vibrates in response to sound waves.

Differentiation

For pupils who grasp concepts quickly, the teacher can ask them to research the common diseases or dysfunctions of each sense organ. For pupils needing more support, the teacher can provide simplified diagrams and allow them to work in pairs to label and describe functions.

Note for teachers using this lesson plan

Ensure that all practical demonstrations involving scents or tastes are done safely and hygienically. Emphasize the importance of protecting sense organs from harm. Encourage pupils to relate the functions of sense organs to their daily experiences and the adaptations seen in other animals.