Lesson Notes By Weeks and Term v3 - Senior Secondary 2
Transportation System
Download the Lessonotes Mobile Nigeria 2025 app for faster lesson access on Android and iPhone.
Transportation System
Download the Lessonotes Mobile Nigeria 2025 app for faster lesson access on Android and iPhone.
Subject: Biology
Class: Senior Secondary 2
Term: 1st Term
Week: 3
Theme: The Organism At Work
This page supports the lesson note with a companion video and a short classroom-ready summary.
For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.
Define diffusion. Explain the in adequacy of diffusionalone as a transportsystem for complexorganisms. Explain the necessity of a transport system in complex or ganisms. Identify source of materials and where the yare transported to Discuss the differenttypes of transportationmedia such as cytoplasm, cell sap,lymph and blood. Describe the mechanisms of transportation in variousanimals. Compare and contrastvarious mechanisms of transportation. Demonstrateexperimentally the flowof materials in plant.
closed systems. Vertebrates (e.g., Fish, Amphibians, Reptiles, Birds, Mammals): Closed Circulatory System Description: Blood is always confined within a network of vessels (arteries, veins, capillaries) and is pumped by a muscular heart. This allows for higher pressure and more efficient, directed flow.
Transport Medium: Blood.
Types of Closed Systems: Fish (Single Circulation): Heart pumps deoxygenated blood to the gills for oxygenation. Oxygenated blood then flows from the gills directly to the rest of the body tissues (systemic circulation) before returning to the heart. Blood passes through the heart once per complete circuit. This results in lower blood pressure to the body tissues. Amphibians & most Reptiles (Incomplete Double Circulation): Have a 3-chambered heart (two atria, one ventricle). The right atrium receives deoxygenated blood from the body, and the left atrium receives oxygenated blood from the lungs/skin. Both bloods mix to some extent in the single ventricle before being pumped out to both lungs/skin and the body. Some mixing of oxygenated and deoxygenated blood occurs. Birds & Mammals (Complete Double Circulation): Have a 4-chambered heart (two atria, two ventricles). This ensures complete separation of oxygenated and deoxygenated blood.
Pulmonary Circulation: Deoxygenated blood from the body is pumped by the right side of the heart to the lungs for oxygenation.
Systemic Circulation: Oxygenated blood from the lungs is pumped by the left side of the heart to all parts of the body. Blood passes through the heart twice per complete circuit. This maintains high blood pressure for efficient delivery to body tissues. 2.
7. Comparing and Contrasting Various Mechanisms of Transportation | Feature | Simple Animals (e.g., Amoeba) | Insects (Open System) | Vertebrates (Closed System) | | :------------------- | :----------------------------------------------------------- | :----------------------------------------------------------- | :------------------------------------------------------------ | | System Complexity | No specialized system; cellular mechanisms | Simple heart, hemocoel, few vessels | Complex heart, extensive network of arteries, veins, capillaries | | Transport Medium | Cytoplasm, extracellular fluid | Hemolymph (blood + interstitial fluid) | Blood | | Oxygen Transport | Directly by diffusion | Not carried by hemolymph; tracheal system for gas exchange | Carried by blood (hemoglobin) | | Blood Confinement | N/A | Not confined to vessels; bathes organs directly | Confined within vessels (arteries, veins, capillaries) | | Blood Pressure | N/A | Low | High (especially in double circulation) | | Efficiency | Efficient for small organisms/short distances | Less efficient for rapid transport due to direct bathing | Highly efficient for rapid, directed transport | | Metabolic Rate | Low | Moderate | High | | Examples | Amoeba, Planaria | Grasshopper, Cockroach | Fish, Frog, Lizard, Bird, Human | Comparison of Plant Transport System (Xylem and Phloem): | Feature | Xylem (Water Transport) | Phloem (Food Transport) | | :--------------- | :----------------------------------------------------------- | :--------------------------------------------------------- | | Substance | Water and dissolved minerals | Sugars (sucrose), amino acids, hormones | | Direction | Unidirectional (mostly upwards from roots to leaves) | Bidirectional (from source to sink, e.g., leaves to roots/fruits) | | Components | Tracheids, vessel elements (dead cells), xylem parenchyma, xylem fibres | Sieve tubes (living cells, no nucleus), companion cells (living), phloem parenchyma, phloem fibres | | Driving Force | Transpiration pull (cohesion-tension theory), root pressure | Pressure flow hypothesis (mass flow) | | Energy | Passive (transpiration is solar energy dependent) | Active (loading/unloading of sugars requires ATP) | 2.
8. Experimental Demonstration of Flow of Materials in Plants This experiment aims to visually demonstrate the upward movement of water in plant stems via xylem vessels.
Title: Demonstration of water transport in a plant stem.
Materials: Freshly cut white-flowered plant stem (e.g., balsam, celery stalk with leaves, hibiscus stem). Beaker or glass jar. Water. Red or blue ink/dye (e.g., eosin solution, food colouring, potassium permanganate). Sharp knife or razor blade. Magnifying glass (optional). * Procedure:
1. Fill the beaker with water and add a few drops of red or blue ink/dye until the water is visibly coloured.
2. Take a freshly cut plant stem. Ensure the cut is clean and made underwater if possible, to prevent air bubbles from stem.
Materials: Freshly cut white-flowered plant stem (e.g., balsam, celery stalk with leaves, hibiscus stem). Beaker or glass jar. Water. Red or blue ink/dye (e.g., eosin solution, food colouring, potassium permanganate). Sharp knife or razor blade. Magnifying glass (optional).
Procedure:
1. Fill the beaker with water and add a few drops of red or blue ink/dye until the water is visibly coloured.
2. Take a freshly cut plant stem. Ensure the cut is clean and made underwater if possible, to prevent air bubbles from entering the xylem.
3. Place the cut end of the stem into the coloured water in the beaker.
4. Leave the setup for several hours (e.g., 2-3 hours) or overnight.
5. After the observation period, remove the stem from the coloured water.
6. Carefully cut transverse sections (thin slices across the stem) at different heights along the stem using a sharp knife.
7. Observe the cut sections with the naked eye or a magnifying glass. Also, observe the veins of the leaves, and if it is a white-flowered plant, the petals might show traces of the dye.
Observation: The teacher and students will observe that the coloured dye has moved up the stem. In the transverse sections, the dye will be concentrated in specific areas, appearing as coloured dots or rings. In the leaves, the veins might appear coloured, and if a flower is present, its petals might show streaks of the dye.
Conclusion: The coloured water moved upwards through the plant stem. The parts that absorbed the dye are the xylem vessels, confirming their role in water and mineral transport in plants. This section provides the detailed content and explanations necessary for the teacher to deliver the lesson effectively without requiring a separate textbook. 2.
1. Definition of Diffusion Diffusion is the net movement of particles (atoms, ions, or molecules) from a region of higher concentration to a region of lower concentration, down a concentration gradient. This movement occurs due to the random kinetic energy of the particles and continues until equilibrium is reached (i.e., particles are evenly distributed). It is a passive process, meaning it does not require metabolic energy from the organism.
Examples relevant to Nigerian contexts: The smell of cooking jollof rice spreading from the kitchen to other parts of a home. Sugar dissolving and spreading evenly in a cup of tea without stirring. The spread of perfume or air freshener in a classroom. 2.
2. Inadequacy of Diffusion as a Transport System for Complex Organisms While diffusion is effective for very small organisms or for short distances, it becomes highly inefficient and inadequate for complex, multicellular organisms due to several factors: Distance: The rate of diffusion is inversely proportional to the square of the distance. For large organisms, the distance between the external environment (or specialized organs like lungs/guts) and the innermost cells is too great for diffusion to supply nutrients and remove wastes at a sufficient rate to meet metabolic demands.
Surface Area to Volume Ratio: Small organisms (e.g., Amoeba, Paramecium) have a large surface area relative to their volume, allowing efficient exchange of materials directly with their environment via diffusion. Complex organisms, however, have a small surface area to volume ratio, meaning most cells are far from the external surface.
Metabolic Demands: Complex organisms have high metabolic rates, requiring a continuous and rapid supply of oxygen and nutrients, and efficient removal of accumulated waste products. Diffusion alone cannot sustain these demands across long distances. If cells rely solely on diffusion, those further from the source of nutrients or oxygen would starve or be poisoned by waste. 2.
3. Necessity of a Transport System in Complex Organisms Given the inadequacies of diffusion, complex organisms require specialized transport systems to: Supply Nutrients: Transport digested food (glucose, amino acids, fatty acids, vitamins, minerals) from the digestive system to all cells for energy, growth, and repair.
Supply Oxygen: Carry oxygen from respiratory organs (lungs, gills) to all body cells for cellular respiration.
Remove Wastes: Transport metabolic waste products (e.g., carbon dioxide, urea, excess water) from cells to excretory organs (lungs, kidneys, skin) for elimination.
Distribute Hormones: Carry hormones (chemical messengers) from endocrine glands to their target cells/organs to regulate various body functions.
Transport Antibodies: Distribute antibodies for defense against pathogens.
Regulate Body Temperature: Distribute heat evenly throughout the body in homeothermic (warm-blooded) animals.
Maintain Homeostasis: Ensure a stable internal environment by regulating the concentration of various substances. 2.
4. Source of Materials and Where They Are Transported To In Plants: Water and Mineral Salts: Source is the soil. Absorbed by root hairs, transported upwards through the xylem vessels to the leaves (for photosynthesis and transpiration) and other growing parts of the plant.
Manufactured Food (Sugars/Photosynthates): Source is the leaves (site of photosynthesis). Transported downwards and to various parts (growing points, storage organs like roots, stems, fruits, and flowers) through the phloem sieve tubes. In Animals (e.g., Mammals): Oxygen: Source is the atmosphere. Absorbed by respiratory organs (lungs), transported by blood (specifically, hemoglobin in red blood cells) to all body cells. Digested Food Nutrients (Glucose, Amino Acids, etc.): Source is the small intestine (after digestion and absorption). Transported by blood plasma to all body cells.
Hormones: Source is endocrine glands. Transported by blood plasma to target organs/cells.
Carbon Dioxide: Source is all body cells (product of cellular respiration). Transported by blood plasma (as bicarbonate ions) and red blood cells back to the lungs for exhalation. Nitrogenous Wastes (e.g., Urea): Source is liver and other body cells (product of protein metabolism). Transported by blood plasma to the kidneys for excretion in urine. 2.
5. Different Types of Transportation Media * Cytoplasm: The jelly-like substance filling a cell. absorption). Transported by blood plasma to all body cells.
Hormones: Source is endocrine glands. Transported by blood plasma to target organs/cells.
Carbon Dioxide: Source is all body cells (product of cellular respiration). Transported by blood plasma (as bicarbonate ions) and red blood cells back to the lungs for exhalation. Nitrogenous Wastes (e.g., Urea): Source is liver and other body cells (product of protein metabolism). Transported by blood plasma to the kidneys for excretion in urine. 2.
5. Different Types of Transportation Media Cytoplasm: The jelly-like substance filling a cell. In unicellular organisms (e.g., Amoeba, Paramecium) and individual cells of multicellular organisms, cytoplasmic streaming (cyclosis) facilitates the movement of organelles, nutrients, and waste within the cell over short distances. This is a form of intracellular transport.
Cell Sap: The fluid found within the large central vacuole of plant cells. It primarily serves as a storage medium for water, nutrients, pigments, and waste products, and helps maintain turgor pressure. While not a primary long-distance transport medium, it plays a role in internal cellular dynamics.
Lymph: A clear, yellowish fluid that circulates in the lymphatic system. It is formed from tissue fluid (interstitial fluid) that leaks out of blood capillaries.
Composition: Contains water, dissolved substances, proteins, fats, and lymphocytes (a type of white blood cell). It lacks red blood cells and large proteins found in blood plasma.
Functions: Drains excess tissue fluid and returns it to the bloodstream, preventing swelling (oedema). Transports absorbed fats from the small intestine (lacteals) to the bloodstream. Plays a crucial role in immunity by transporting lymphocytes and filtering pathogens in lymph nodes.
Blood: The main transport medium in most multicellular animals. It is a specialized connective tissue.
Composition: Plasma (about 55%): Watery fluid containing dissolved proteins (albumins, globulins, fibrinogen), glucose, amino acids, mineral salts, hormones, enzymes, antibodies, oxygen, carbon dioxide, and waste products (urea). Blood Cells (about 45%): Red Blood Cells (Erythrocytes): Biconcave, anucleated (in mammals), contain hemoglobin for oxygen transport.
White Blood Cells (Leukocytes): Involved in immunity and defense against pathogens. (e.g., neutrophils, lymphocytes, monocytes, eosinophils, basophils).
Platelets (Thrombocytes): Cell fragments involved in blood clotting.
Functions: Transport of oxygen from lungs to tissues. Transport of carbon dioxide from tissues to lungs. Transport of digested food from gut to tissues. Transport of nitrogenous wastes from tissues to excretory organs. Transport of hormones. Defense against diseases (white blood cells, antibodies). Regulation of body temperature. Blood clotting. 2.
6. Mechanisms of Transportation in Various Animals Simple Animals (e.g., Amoeba, Hydra, Planaria): These organisms rely primarily on diffusion, osmosis, and active transport directly between their cells and the external environment. Amoeba exhibits cytoplasmic streaming (cyclosis) to move materials within its single cell. Hydra and Planaria have simple body plans with a large surface area to volume ratio, allowing direct exchange across their body surfaces or gastrovascular cavity. They lack specialized circulatory systems. Insects (e.g., Grasshopper, Cockroach): Open Circulatory System Description: Blood (more accurately, hemolymph) is not always confined within vessels. It is pumped by a tubular heart (dorsal vessel) into a large body cavity called the hemocoel, where it bathes the organs directly. The hemolymph then re-enters the heart through pores (ostia) with valves.
Transport Medium: Hemolymph, which is a mixture of blood and interstitial fluid. It carries nutrients, hormones, and wastes, but typically not oxygen (gas exchange is handled by a separate tracheal system).
Efficiency: Less efficient due to lower pressure and less directed flow compared to closed systems. Vertebrates (e.g., Fish, Amphibians, Reptiles, Birds, Mammals): Closed Circulatory System Description: Blood is always confined within a network of vessels (arteries, veins, capillaries) and is pumped by a muscular heart. This allows for higher pressure and more efficient, directed flow.
Transport Medium: Blood.
Types of Closed Systems: Fish (Single Circulation): Heart pumps deoxygenated blood to the gills for oxygenation. Oxygenated blood then flows from the gills directly to the rest of the body tissues (systemic circulation) before returning to the heart. Blood passes through the
Human Health and Disease Management: Understanding the transportation system (specifically blood circulation) is critical for diagnosing and managing common health issues in Nigeria. For example, hypertension (high blood pressure) is a major public health concern; knowledge of how blood flows through arteries helps in understanding its causes and treatments. Similarly, conditions like sickle cell anemia, prevalent in some Nigerian communities, directly affect the ability of red blood cells to transport oxygen effectively. Blood donation drives rely on the understanding of blood as a transport medium to save lives.
Agriculture and Crop Productivity: For farmers in Nigeria, knowledge of how water and nutrients are transported within plants is essential for optimizing crop yield. This informs practices such as efficient irrigation (ensuring water reaches plant roots for xylem transport), appropriate fertilizer application (dissolved minerals transported by xylem), and understanding the effects of plant diseases or pests that might block vascular bundles (e.g., cassava mosaic disease affecting nutrient transport).
Food Preservation Techniques: Traditional Nigerian food preservation methods often involve manipulating diffusion. For instance, salting or sun-drying fish (e.g., 'Eja kika' or 'Eja didan') relies on osmosis (a special type of diffusion) to draw water out of the fish, inhibiting microbial growth. Understanding diffusion helps explain why these methods are effective in preserving perishable food items.