Lesson Note on Respiratory System: Mechanism in Higher and Lower Animals for SSS 2

Class: Senior Secondary School 2 (SS2 / SSS2)
Term: 1st Term
Week: 6
Age: 16 years
Duration: 45 minutes
Subject: Biology
Curriculum Theme: Physiology of Living Organisms
Previous Lesson: Respiratory System: Types of Respiratory Systems.
Topic: RESPIRATORY SYSTEM CONTINUES
Subject Matter: Mechanism of respiration in higher animals (inhalation and exhalation) and mechanism of respiration in lower animals.

Specific Objectives

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

Cognitive Domain:

• Describe the mechanism of inhalation in higher animals.
• Describe the mechanism of exhalation in higher animals.
• State the respiratory organs and mechanisms of selected lower animals.

Affective Domain:

• Appreciate the diverse adaptations for respiration in different animals.
• Value the importance of efficient respiratory systems for survival.

Psychomotor Domain:

• Identify respiratory organs of various animals from diagrams or prepared slides.
• Sketch the basic structure of a respiratory organ from a lower animal.

Social Domain:

• Participate in discussions about the similarities and differences in respiratory mechanisms.

Reference Materials

The following resources were used in planning this lesson:

• Senior Secondary Schools Education Curriculum
• State Unified Scheme of Work
• Essential Biology for Senior Secondary Schools by M.C. Michael

Instructional Materials

The teacher will teach this lesson with the aid of:

• Textbook
• Posters showing the human respiratory system and various animal respiratory organs
• Prepared slides showing respiratory organs of earthworm, tilapia, toad, grasshopper, and rat (if available)
• Microscope (if prepared slides are used)

Rationale for the Lesson

Understanding the mechanism of respiration helps pupils know how living organisms obtain oxygen and release carbon dioxide. This knowledge is important for appreciating the physiological adaptations that allow different animals to survive in their various environments.

Prerequisite/Previous Knowledge

Pupils should have prior knowledge of the definition of respiration, the types of respiration (aerobic and anaerobic), and the general structure of the human respiratory system.

Lesson Content/Board Summary

MECHANISM OF RESPIRATION

Mechanism of Respiration in Higher Animals (e.g., Humans)

Respiration in higher animals involves two main phases: Inhalation (inspiration) and Exhalation (expiration).

Inhalation (Inspiration)

This is the process by which air is drawn into the lungs. It involves the following steps:

• The diaphragm contracts and flattens, moving downwards.
• The external intercostal muscles contract, pulling the rib cage upwards and outwards.
• These actions increase the volume of the thoracic cavity (chest cavity).
• The increase in volume causes a decrease in air pressure within the lungs compared to the atmospheric pressure.
• Air from the outside then rushes into the lungs through the nose/mouth, trachea, and bronchi until the pressure equalizes.

Exhalation (Expiration)

This is the process by which air is expelled from the lungs. It involves the following steps:

• The diaphragm relaxes and moves upwards, becoming dome-shaped.
• The external intercostal muscles relax, allowing the rib cage to move downwards and inwards.
• These actions decrease the volume of the thoracic cavity.
• The decrease in volume causes an increase in air pressure within the lungs compared to the atmospheric pressure.
• Air is then forced out of the lungs until the pressure equalizes with the atmosphere.

Mechanism of Respiration in Lower Animals

Lower animals exhibit diverse respiratory mechanisms adapted to their specific habitats.

• Earthworm: Respires through its moist skin (cutaneous respiration). Oxygen diffuses through the thin, moist cuticle into the blood capillaries, while carbon dioxide diffuses out.
• Tilapia (Fish): Respires using gills. Water containing dissolved oxygen enters through the mouth and flows over the gill filaments. Oxygen diffuses from the water into the blood capillaries in the gills, and carbon dioxide diffuses from the blood into the water. The operculum then pushes the water out.
• Toad (Amphibian): Respires using three main methods:
  • Cutaneous respiration: Through its moist skin, especially when submerged in water or during hibernation.
  • Buccal respiration: Through the lining of its mouth cavity, by moving the floor of the mouth.
  • Pulmonary respiration: Using simple lungs, especially on land.
• Grasshopper (Insect): Respires using a tracheal system. Air enters and leaves the body through small openings called spiracles, located along the sides of the abdomen and thorax. These spiracles lead into a network of tubes called tracheae, which branch into smaller tracheoles that directly supply oxygen to the body cells.
• Rat: As a mammal, the rat’s respiratory mechanism is similar to that of humans, involving lungs, diaphragm, and intercostal muscles for inhalation and exhalation.

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 greets the pupils and reminds them of the previous lesson on the respiratory system. The teacher then asks pupils to briefly explain what respiration is.
Pupils’ Activity: Pupils respond to the greeting and briefly explain their understanding of respiration.
Learning Point: Pupils recall prior knowledge of respiration.

Step 2: Presentation of Higher Animal Respiration

Time: 10 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher introduces the mechanism of respiration in higher animals, focusing on humans. The teacher explains the roles of the diaphragm and intercostal muscles during inhalation.
Pupils’ Activity: Pupils listen attentively and observe any diagrams or posters shown by the teacher.
Learning Point: Pupils understand the initial stages of breathing in higher animals.

Step 3: Discussion of Mechanism of Inhalation

Time: 5 minutes
Teaching Skill: Explanation/Questioning
Teacher’s Activity: The teacher further elaborates on the process of inhalation, explaining how changes in thoracic cavity volume and pressure lead to air entering the lungs.
Pupils’ Activity: Pupils ask questions for clarification and note down key points.
Learning Point: Pupils grasp the detailed steps of inhalation.

Step 4: Discussion of Mechanism of Exhalation

Time: 5 minutes
Teaching Skill: Explanation/Comparison
Teacher’s Activity: The teacher explains the mechanism of exhalation, drawing comparisons and contrasts with inhalation, emphasizing the relaxation of muscles and decrease in thoracic volume.
Pupils’ Activity: Pupils listen, compare the two processes, and contribute to the discussion.
Learning Point: Pupils understand the detailed steps of exhalation.

Step 5: Presentation of Lower Animal Respiration

Time: 8 minutes
Teaching Skill: Demonstration/Visualisation
Teacher’s Activity: The teacher introduces the concept of diverse respiratory mechanisms in lower animals. The teacher shows prepared slides or diagrams of respiratory organs of earthworm, tilapia, toad, and grasshopper.
Pupils’ Activity: Pupils observe the slides or diagrams and identify the different respiratory organs.
Learning Point: Pupils are exposed to the variety of respiratory structures in lower animals.

Step 6: Observation and Discussion of Lower Animals

Time: 7 minutes
Teaching Skill: Guidance/Discussion
Teacher’s Activity: The teacher guides pupils to discuss and compare the different mechanisms of respiration in each lower animal, highlighting adaptations to their environment.
Pupils’ Activity: Pupils discuss their observations, compare the mechanisms, and ask questions about specific adaptations.
Learning Point: Pupils understand the specific respiratory mechanisms of various lower animals.

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. Describe the sequence of events during inhalation in humans.
2. How does exhalation differ from inhalation in terms of muscle action and pressure changes?
3. State the respiratory organ of an earthworm and explain how it respires.
4. Mention two respiratory organs used by a toad and briefly explain one.

Pupils’ Activity: Pupils answer orally and in writing.
Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 0 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher briefly summarizes the key points of the lesson, emphasizing the different mechanisms of respiration in higher and lower animals. The teacher assigns homework: Draw and label the tracheal system of a grasshopper.
Pupils’ Activity: Pupils listen to the summary and copy down the homework.
Learning Point: Pupils consolidate their learning and prepare for independent study.

Lesson Keywords

• Inhalation – The process of taking air into the lungs.
• Exhalation – The process of expelling air from the lungs.
• Diaphragm – A dome-shaped muscle that separates the thoracic cavity from the abdominal cavity, important for breathing.
• Intercostal muscles – Muscles located between the ribs that aid in breathing.
• Thoracic cavity – The chest cavity containing the lungs and heart.
• Gills – Specialized respiratory organs found in aquatic animals like fish.
• Spiracles – External openings in the body of insects through which air enters the tracheal system.
• Trachea – A network of tubes that transport air directly to the cells in insects.
• Cutaneous respiration – Respiration through the skin.
• Buccal respiration – Respiration through the lining of the mouth cavity.
• Pulmonary respiration – Respiration through the lungs.

Differentiation

For pupils who are fast learners, the teacher can challenge them to research and explain gas exchange at the alveolar level in humans or compare the efficiency of different respiratory systems. For pupils who need more support, the teacher can provide simplified diagrams and allow them to work in pairs to describe the mechanisms, offering additional guidance and visual aids.

Note for teachers using this lesson plan

Ensure that the instructional materials, especially diagrams or prepared slides, are clear and visible to all pupils. Encourage active participation and questioning to foster a deeper understanding of the diverse respiratory mechanisms. Emphasize the connection between an animal’s habitat and its respiratory adaptations.