Comparative advantage is a fundamental concept in international trade and economics, introduced by the British economist David Ricardo in 1817. It explains how and why countries engage in trade, even when one country can produce all goods more efficiently than another. The theory posits that countries should specialize in producing goods where they have the lowest opportunity cost, thereby maximizing global efficiency and benefiting all parties involved. This principle underpins much of modern economic policy and global trade practices. Theoretical Foundations Absolute vs. Comparative Advantage Before delving into comparative advantage, it's essential to understand its distinction from absolute advantage. Absolute advantage occurs when a country can produce a good using fewer resources than another country. In contrast, comparative advantage focuses on opportunity costs—the cost of forgoing the next best alternative when making a decision. A country has a comparative advantage in producing a good if it has a lower opportunity cost compared to others. David Ricardo's Model Ricardo's model simplifies the complexities of international trade by assuming two countries and two goods. He demonstrated that even if one country holds an absolute advantage in producing both goods, trade can still be beneficial if each country specializes in the good where it has a comparative advantage. This specialization leads to more efficient resource allocation and increased overall production. Opportunity Cost and Its Role Opportunity cost is central to the concept of comparative advantage. It represents the value of the next best alternative foregone when a decision is made. By comparing opportunity costs, countries can determine in which goods they have a comparative advantage. This analysis encourages specialization and trade, leading to a more efficient global economy. Real-World Applications Case Study: Portugal and England Ricardo's original example involved Portugal and England. Portugal could produce both wine and cloth more efficiently than England. However, the opportunity cost of producing wine was lower in Portugal, while England had a lower opportunity cost in producing cloth. By specializing and trading, both countries could consume more of both goods than if they tried to produce everything domestically. Modern Examples United States and Bangladesh: The U.S. specializes in high-tech industries like software and aerospace, while Bangladesh focuses on textile manufacturing. Despite the U.S. having the capability to produce textiles efficiently, its opportunity cost is higher due to the potential loss in high-tech production. Therefore, both countries benefit by specializing and trading. Brazil and Canada: Brazil's favorable climate makes it ideal for coffee production, while Canada's vast forests make it a leader in timber production. By specializing in these areas and trading, both nations can enjoy a greater variety of goods at lower costs. ,,....

1. NON SPECIFIC IMMUNE SYSTEM
BY: ISHA JAFFAR

2. NON SPECIFIC DEFENCE
Response to all the microbes and does not act against particular microbe.
None specific defense is shown by
1. Skin and mucous membrane
• Skin act as barrier
• Bacteria and virous cannot penetrate it
• Skin has glands. These glands oil and sweat. They keep the PH of skin from 3 to 5.
• Saliva, tear and mucous secretion bathe the exposed surfaces and remove the bacteria and virous.
• Saliva and mucous secretions have antimicrobial proteins called lysozymes. Lysozyme is an enzyme. It attacks on the
walls of bacteria and destroy them.
• Mucous is a thick fluid.
• The gastric juice is produced by stomach. It is highly acidic. It kills most the microbes present in the food.

3. 2. Phagocytic white blood cells and natural killer cells
The internal mechanism of nonspecific defense mostly depends on phagocytosis.
Following white blood cells play role in the internal nonspecific defense.
1. Neutrophils
• Phagocytic cells called neutrophils. They are about 60% to 70% of the total blood cells.
• Neutrophils leave the blood and infected tissue by amoeboid movement.
• They destroy the microbes there.
2. Monocytes
• 5 % of the white blood cells.
• Provide effective phagocytic defense. circulate in the blood for a few hours after maturing. They are
enlarged and developed into macrophages.
• Some macrophages live permanently in organs and connective tissues. They are called alveolar
macrophages in lungs. They are called Kupffers cells in liver
3. Eosinophils
• 1.5% of white blood cells. They are only limited phagocytic activity.
• Contain destructive enzymes within cytoplasmic granules.

4. 3. Antimicrobial proteins
• These protein attack directly the invading pathogens.
TYPES
1. Complement
• Group of 20 proteins. Work with other defense mechanism.
• Destroy microbes by lysis
2. Interferon
• Produced by virous infected cells.
• Produce resistance in the other cells against the attack of virous
• Some interferon produced by recombinant DNA technology.
• They are used against Hepatitis and Cancer.

5. 4. Inflammatory response
• Response shown by tissues, injured by physical injury is called inflammatory response.
• Type of nonspecific response.
• Small blood vessels near the injury dilate.
• They increase the blood supply to injured part.
• It causes edema(swelling).
• Inflammatory process is started by chemical signals.
• One of the chemical signal is histamine.
• Histamine is released by basophils or mast cells.
• It causes vasodilation.
• Some white blood cells also release prostaglandins.
• They increase the temperature of the swelled part.
• Now pathogens reach the spot.
• Some white blood cells also released pyrogens.