Objectives (5 - 10 minutes)

1. Understanding of the circulatory system in animals: The teacher must ensure that students understand the basic structure and functions of the circulatory system in animals, including blood circulation, lymphatic system, and the role of the heart.

2. Differentiation of types of circulatory systems: Students should be able to differentiate the three main types of circulatory systems (open, closed, and mixed) and understand the distinct characteristics of each.

3. Application of knowledge: The final objective is for students to apply the acquired knowledge to understand how the circulatory system contributes to the health and well-being of animals.

Secondary objectives:

• Stimulation of critical thinking: The teacher should encourage students to question and analyze the information presented, thus developing their critical thinking.

• Promotion of active participation: The teacher should encourage active participation of students through discussions and practical activities to ensure a better understanding of the subject.

Introduction (10 - 15 minutes)

1. Review of previous contents: The teacher should start the lesson by briefly reviewing the concepts of cells, tissues, and organs, as they are fundamental for understanding the circulatory system. Quick questions or interactive activities can be used to assess students' prior knowledge.

2. Problem situations: The teacher can propose two situations that arouse students' interest and motivate them to learn about the circulatory system. For example:

   • "How do you think blood manages to reach all parts of the body, from the fingertips to the brain, in such a short time?"
   • "Why do some animals, like fish, have such thin skin that we can see blood vessels through it, while others, like us humans, have thicker skin, making blood vessels invisible?"

3. Contextualization: The teacher should explain the importance of the circulatory system in daily life, highlighting how it contributes to the health and well-being of animals, including humans. It can be mentioned how the circulatory system is involved in processes such as wound healing, body temperature control, and disease response.

4. Introduction to the topic: To spark students' interest, the teacher can share some curiosities about the circulatory system. For example:

   • "Did you know that the largest artery in the human body, the aorta, is almost 3 centimeters in diameter and is long enough to wrap around the Earth twice?"
   • "Did you know that the blood circulation of fish is very different from ours? While our blood is pumped by the heart, fish blood is pumped by the gills!"

5. Lesson objectives: Finally, the teacher should present the learning objectives of the lesson, explaining that students will learn about the structure and functions of the circulatory system in animals, and how to differentiate the three types of circulatory systems.

Development (20 - 25 minutes)

1. Theory - Circulatory System in Animals (10 - 12 minutes):

   • Definition: The teacher should start by explaining that the circulatory system is a set of organs and tissues that transport nutrients, oxygen, hormones, and other substances to the body's cells and remove metabolic waste from them.
   • Main Organs: Next, the teacher should introduce the main organs of the circulatory system: heart, blood vessels, and blood. The function of each should be briefly explained, as well as how they are interconnected.
   • Blood and Lymphatic Circulation: The teacher should then discuss blood and lymphatic circulation, explaining how blood and lymph circulate through the body and their specific functions.
   • Types of Circulatory System: The teacher should introduce the three types of circulatory systems: open, closed, and mixed. The characteristics of each should be explained, such as the presence or absence of blood vessels and the direction of blood flow.
   • The Role of the Heart: Finally, the teacher should delve into the discussion about the heart, explaining its structure and function in more detail. It should be highlighted that the heart is the central organ of the circulatory system, pumping blood throughout the body.

2. Activity - Modeling a Circulatory System (5 - 7 minutes):

   • Materials: The teacher should provide students with modeling clay in different colors (for example, red to represent blood, blue to represent lymph), straws, paper, and pens.
   • Instructions: The teacher should instruct students to use the clay to create a simple model of the circulatory system, including the heart, blood vessels, and heart chambers. They should also use the straws to represent blood vessels and lymph.
   • Discussion: While students are working on their models, the teacher should move around the room, asking guiding questions and encouraging discussion. For example, "How do you think blood flows through the circulatory system?" or "Why does the heart have different chambers?"
   • Presentation: At the end of the activity, students should present their models to the class, explaining the different parts and how they work together.

3. Theory - Application of the Circulatory System (5 - 6 minutes):

   • Importance for Life: The teacher should emphasize the importance of the circulatory system for life, explaining how it allows animals to receive the necessary nutrients and oxygen and remove metabolic waste.
   • Relation to Health: The teacher should discuss how problems in the circulatory system can affect health, citing examples such as hypertension, atherosclerosis, and anemia.
   • Comparison between Species: The teacher should briefly compare the circulatory systems of different species, highlighting the adaptations that allow each species to survive in its specific environment.

Return (10 - 15 minutes)

1. Concepts Review (5 - 7 minutes): The teacher should review the main concepts covered in the lesson, reinforcing the structure and functions of the circulatory system in animals, the differentiation of types of circulatory systems, and the importance of the circulatory system for the health and well-being of animals. A whiteboard or a slide presentation can be used to visually summarize the main concepts. The teacher can also ask students to share what they have learned, thus reinforcing the acquired knowledge.

2. Connection to Practice (3 - 5 minutes): The teacher should then lead a discussion to connect the learned theory with practice. Students can be asked how they think the learned concepts apply to everyday situations or phenomena observed in nature. For example:

   • "How does the circulatory system help athletes perform well during sports?"
   • "How do animals living in very cold or very hot environments have their circulatory systems adapted to withstand these conditions?"

3. Final Reflection (2 - 3 minutes): To ensure that students have assimilated the content, the teacher should propose that they reflect on the following questions:

   1. "What was the most important concept you learned today?"
   2. "What questions have not been answered yet?" Students can be asked to write down their answers, which will be useful for planning the next lesson or activity.

4. Feedback (2 - 3 minutes): Finally, the teacher should request feedback from students about the lesson. They can be asked what they found most interesting or challenging, if they felt they learned enough, and if they have any suggestions to improve future lessons. Student feedback is valuable for the teacher to enhance their teaching strategies and make lessons more effective and enjoyable.

Conclusion (5 - 7 minutes)

1. Summary of Contents (2 - 3 minutes): The teacher should summarize the main points covered during the lesson. This includes the definition and function of the circulatory system in animals, the differentiation of types of circulatory systems, blood and lymphatic circulation, and the role of the heart. A whiteboard or a slide presentation can be used to visually reinforce the concepts.

2. Connection between Theory, Practice, and Applications (1 - 2 minutes): The teacher should emphasize how the lesson connected the theory, practice, and applications of the circulatory system. It should be highlighted how modeling the circulatory system helped students visualize and better understand the structure and function of the circulatory system. Additionally, the teacher should reinforce the importance of the circulatory system in daily life and in various aspects of animal health and well-being.

3. Additional Materials (1 - 2 minutes): The teacher should suggest additional study materials for students who wish to deepen their knowledge of the circulatory system. This may include biology books, educational videos, science websites, and interactive learning apps. For example, the teacher can recommend a documentary on human anatomy that explains in detail how the circulatory system works.

4. Importance of the Subject (1 minute): Finally, the teacher should reinforce the importance of the circulatory system for the life and health of animals, including humans. It should be emphasized that the circulatory system is essential for maintaining life, as it provides the necessary nutrients and oxygen for the proper functioning of all cells in the body, and removes metabolic waste. The teacher can conclude the lesson by reminding students to take good care of their bodies, as this includes keeping the circulatory system healthy.