JAMB Biology Note- Transport
Topic: Transport
Table of Contents
- A. Need for Transportation
- B. Materials for Transportation
- Summary of Transportation Materials
- C. Channels for Transportation
- D. Plant Vascular System (Phloem and Xylem)
- E. Media and Processes for Transportation
- Summary Table: Comparison of Transportation Mechanisms
- Conclusion
A. Need for Transportation
As organisms grow larger and more complex, they encounter challenges in transporting materials such as nutrients, gases, and waste products. In simple organisms, diffusion is sufficient to transport materials, but as size and complexity increase, more efficient systems are needed.
Why Transportation is Needed:
- To meet metabolic demands: Larger organisms have higher metabolic rates, which require efficient systems to deliver oxygen, nutrients, and hormones to cells and remove waste products.
- To maintain homeostasis: The transport system helps maintain a stable internal environment by distributing nutrients and removing waste products.
- To allow for specialized functions: As organisms develop different tissues and organs, transportation is needed to support their specialized functions (e.g., muscle contraction, enzyme activity).
Factors Leading to the Need for a Transport System:
- Size and Complexity: Small, simple organisms rely on diffusion alone for nutrient and gas exchange. However, larger organisms need a transport system due to the difficulty of diffusion over long distances.
- Increased metabolic demands: As an organism grows in size, its cells require more oxygen and nutrients, and produce more waste. Diffusion becomes inefficient for transporting these materials across larger distances.
- Organ specialization: In complex organisms, cells become specialized, and their functions often require specific nutrients, gases, or hormones that need to be transported efficiently to different body parts.
B. Materials for Transportation
Various substances are transported within plants and animals to ensure proper functioning, growth, and survival. These materials include:
- Excretory Products
- Waste Products: Nitrogenous wastes (e.g., urea, uric acid) are excreted and transported to the excretory organs (e.g., kidneys in animals, vacuoles in plants) for elimination.
- Forms of Transport: Excretory products are transported through blood (in animals) or vacuoles and xylem/phloem (in plants).
- Gases
- Oxygen and Carbon Dioxide: Oxygen is transported from the lungs to body cells (in animals) or from the leaves to other parts of the plant. Carbon dioxide is transported in the opposite direction, from body cells to the lungs (in animals) or from the plant to the atmosphere.
- Forms of Transport: In animals, oxygen is transported by red blood cells (hemoglobin). In plants, gases move through stomata and other tissues.
- Manufactured Food (In Plants)
- Glucose: Plants produce glucose through photosynthesis. This glucose is then transported to non-photosynthesizing parts of the plant, such as roots, stems, and fruits.
- Forms of Transport: Glucose is transported via the phloem in plants, a process called translocation.
- Digested Food (In Animals)
- Nutrients: After food is digested in the alimentary canal, nutrients like glucose, amino acids, and fatty acids are absorbed into the bloodstream.
- Forms of Transport: Nutrients are transported by blood to various tissues and organs for assimilation and storage.
- Nutrients
- Minerals and Vitamins: Essential for various biochemical processes in plants and animals.
- Forms of Transport: In animals, nutrients are transported through the circulatory system. In plants, minerals are transported through the xylem.
- Water
- Importance: Water is vital for maintaining cellular functions, nutrient transport, and temperature regulation.
- Forms of Transport: In plants, water is transported via the xylem from roots to leaves. In animals, water is transported through blood and lymph.
- Hormones
- Signaling Molecules: Hormones regulate growth, metabolism, and other body functions in both plants and animals.
- Forms of Transport: In animals, hormones are transported via the bloodstream. In plants, hormones like auxin are transported through phloem and specialized plant tissues.
Summary of Transportation Materials
| Material | Source | Forms of Transport | Destination |
|---|---|---|---|
| Excretory Products | Cells (e.g., nitrogenous wastes) | Blood (animals), vacuoles (plants) | Excretory organs (kidneys, vacuoles) |
| Gases (Oxygen & COâ‚‚) | Lungs/Leaves | Blood (animals), stomata (plants) | Cells (animals), atmosphere (plants) |
| Manufactured Food | Leaves | Phloem (plants) | Roots, stems, fruits (plants) |
| Digested Food | Alimentary canal | Blood (animals) | Cells and tissues (animals) |
| Nutrients | Digestive system (animals), soil (plants) | Blood (animals), xylem (plants) | Cells and tissues (both) |
| Water | Soil (plants), body fluids (animals) | Xylem (plants), blood (animals) | Cells (both) |
| Hormones | Glands (animals), tissues (plants) | Blood (animals), phloem/xylem (plants) | Target tissues (both) |
C. Channels for Transportation
i. Mammalian Circulatory System (Heart, Arteries, Veins, and Capillaries)
The mammalian circulatory system is a closed, double circulatory system consisting of the heart, arteries, veins, and capillaries. It is responsible for transporting oxygen, nutrients, hormones, and waste products throughout the body.
- Heart:
The heart pumps blood throughout the body. It consists of four chambers:- Left atrium: Receives oxygenated blood from the lungs.
- Right atrium: Receives deoxygenated blood from the body.
- Left ventricle: Pumps oxygenated blood to the body.
- Right ventricle: Pumps deoxygenated blood to the lungs for oxygenation.
- Arteries:
- Carry oxygenated blood from the heart to the body (except for the pulmonary artery, which carries deoxygenated blood).
- Have thick, elastic walls to withstand high pressure.
- Major arteries include the aorta, which carries oxygen-rich blood to the body.
- Veins:
- Carry deoxygenated blood back to the heart (except for the pulmonary veins, which carry oxygenated blood).
- Have thinner walls than arteries and contain valves to prevent backflow.
- Major veins include the superior and inferior vena cava, which return deoxygenated blood to the right atrium.
- Capillaries:
- Microscopic blood vessels that connect arteries and veins.
- Exchange gases, nutrients, and waste products between blood and body tissues.
ii. Functions of Specific Blood Vessels
- Hepatic Portal Vein:
- Carries nutrient-rich blood from the digestive organs to the liver for detoxification and storage.
- Enables the liver to regulate blood composition before returning it to the general circulation.
- Pulmonary Vein and Artery:
- Pulmonary artery: Carries deoxygenated blood from the right ventricle to the lungs for oxygenation.
- Pulmonary vein: Carries oxygenated blood from the lungs to the left atrium of the heart.
- Aorta:
- The largest artery in the body, carrying oxygenated blood from the left ventricle to the rest of the body.
- Renal Artery and Vein:
- Renal artery: Carries oxygenated blood to the kidneys, where waste filtration and water balance occur.
- Renal vein: Carries filtered blood back from the kidneys to the inferior vena cava.
D. Plant Vascular System (Phloem and Xylem)
The vascular system in plants consists of xylem and phloem, which are responsible for the transport of water, minerals, and food throughout the plant.
- Xylem:
- Transports water and dissolved minerals from the roots to the rest of the plant.
- Composed of vessel elements, tracheids, and fibers.
- Xylem transport occurs through transpiration pull, root pressure, and capillary action.
- Xylem tissue is lignified, which provides structural support to plants.
- Phloem:
- Transports the products of photosynthesis (mainly sugars like sucrose) from the leaves to other parts of the plant.
- Composed of sieve tube elements, companion cells, phloem fibers, and phloem parenchyma.
- Phloem transport occurs through active transport mechanisms and the pressure flow hypothesis.
E. Media and Processes for Transportation
- Media of Transportation:
- Cytoplasm: A gel-like substance within the cell that allows the diffusion of nutrients and waste products.
- Cell Sap: The liquid found in vacuoles of plant cells, transporting nutrients and waste.
- Body Fluids: In animals, body fluids such as interstitial fluid and lymph help transport nutrients and waste between cells and tissues.
- Blood: The main transport medium in animals, carrying gases, nutrients, waste, and hormones to and from cells.
- Composition and Functions of Blood and Lymph:
- Blood: Composed of plasma (water, proteins, and dissolved gases), red blood cells (carry oxygen), white blood cells (immune response), and platelets (blood clotting).
- Lymph: Composed of lymphocytes (immune function), water, and dissolved substances, it helps in the immune response and the transport of fats from the digestive system.
- Mechanisms of Transportation:
- Diffusion: Movement of particles from an area of high concentration to an area of low concentration. Used in gas exchange and nutrient uptake.
- Osmosis: Movement of water across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration.
- Plasmolysis: The shrinkage of the cytoplasm in plant cells due to water loss.
- Turgidity: The rigidity of plant cells due to water uptake, maintaining plant cell structure.
- Comparing Mechanisms of Transportation in Plants and Animals:
- Open Circulatory Systems in Animals: Found in arthropods and mollusks, where body fluids (hemolymph) directly bathe tissues and organs for exchange of nutrients and gases. There is no distinction between blood and interstitial fluid.
- Transpiration Pull in Plants: The process by which water is drawn up from the roots through the xylem due to the evaporation of water from the leaves.
- Root Pressure in Plants: The pressure generated by the osmotic uptake of water into the roots, pushing water up the plant.
- Active Transport in Plants: The process by which plant cells use energy to move ions and other substances across cell membranes, allowing nutrient uptake from the soil.
Summary Table: Comparison of Transportation Mechanisms
| Mechanism | In Animals | In Plants |
|---|---|---|
| Diffusion | Gases (oxygen, carbon dioxide) across cell membranes | Gas exchange through stomata in leaves |
| Osmosis | Water movement between cells | Water uptake by roots and movement through tissues |
| Plasmolysis | Not applicable in most animals | Occurs when plant cells lose water and shrink |
| Turgidity | Not applicable in animals | Plant cells become turgid with water intake |
| Open Circulatory System | Arthropods and mollusks (hemolymph) | Not applicable |
| Transpiration Pull | Not applicable | Water drawn through xylem from roots to leaves |
| Root Pressure | Not applicable | Osmotic pressure in roots pushes water upwards |
| Active Transport | Absorption of ions in cells (e.g., in kidneys) | Uptake of minerals in roots |
Conclusion
In both plants and animals, transportation is essential for the survival and functioning of the organism. The mechanisms involved in transportation, whether it is the mammalian circulatory system or the plant vascular system, ensure that nutrients, gases, water, and waste are properly distributed and eliminated. The various media (blood, lymph, cytoplasm, cell sap) and processes (diffusion, osmosis, active transport) facilitate the movement of materials within and across cells, maintaining homeostasis and promoting growth.
