Transport System

Transportation is the movement of substances from one part of an organism's body to another.

Small, single-celled organisms with a large surface area-to-volume ratio relies on simple diffusion and cytoplasmic streaming to move materials. However, as organisms grow larger, more complex transport systems become necessary, as simple diffusion is no longer efficient.

Why Transport Systems Are Needed

1. To obtain essential materials like oxygen, water, and nutrients.
2. To move water and minerals from the soil through plant roots to other parts of the plant.
3. To remove metabolic waste, such as carbon dioxide, urea, and water.
4. To transfer hormones from their production site to their target locations.
5. To distribute glucose and other nutrients to various parts of the plant.

Materials Transported in Animals

1. Oxygen
2. Carbon dioxide
3. Urea
4. Excess salts
5. Amino acids
6. Water
7. Fatty acids and glycerol
8. Hormones
9. Sugars
10. Antibodies

Materials Transported in Plants

1. Water
2. Amino acids
3. Manufactured food
4. Minerals
5. Hormones
6. Glucose and lipids

Transport Mediums

1. Cytoplasm: Used by lower unicellular organisms like Amoeba and Paramecium to transport materials.
2. Cell sap or latex: The medium for transporting materials in plants.
3. Blood: The primary medium for transporting materials in most animals.
4. Lymph: Found in higher animals, lymph is a fluid rich in white blood cells (lymphocytes). It returns to the bloodstream via the subclavian vein after passing through lymph nodes, where it is purified.

Circulatory Systems

The circulatory system ensures the continuous flow of blood in the body, involving the heart and blood vessels. There are two types:

• Open Circulatory System: Blood vessels lead out of the heart but end in spaces where blood comes in direct contact with cells. This system is found in arthropods and some mollusks.
• Closed Circulatory System: Blood flows within a network of arteries, capillaries, and veins. Blood is confined within vessels and does not directly contact cells. There are two subtypes:
  • Single Circulatory System: Blood passes through the heart once during a complete circulation.
  • Double Circulatory System: Blood passes through the heart twice during one circulation. This includes:
    • Pulmonary Circulation: Blood moves between the heart and lungs.
    • Systemic Circulation: Blood moves between the heart and the rest of the body.

Components of Blood

Blood is a fluid tissue composed of two main parts: blood cells (solid) and plasma (liquid).

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Blood Cells

1. Red Blood Cells (Erythrocytes): Small, disc-shaped cells without a nucleus. They contain hemoglobin, which binds to oxygen in the lungs and releases it in low-oxygen areas. These cells are produced in the bone marrow and live for about 120 days.
2. White Blood Cells (Leucocytes): These cells, produced in the bone marrow, lymph nodes, or spleen, defend the body. Types include:
   • Lymphocytes: Produce antibodies to target and kill germs.
   • Phagocytes: Ingest bacteria, viruses, and dead cells through a process called phagocytosis.
3. Platelets (Thrombocytes): Small cell fragments without a nucleus that aid in blood clotting. Platelets release enzymes that help form fibrin, which seals wounds.

Plasma: A pale yellow liquid mostly made of water, it transports proteins, waste materials, nutrients, gases, hormones, and salts throughout the body.

Transport Tissues in Animals

Blood vessels transport blood throughout the body. They include:

1. Arteries: Thick-walled and elastic vessels that carry oxygenated blood from the heart (except the pulmonary artery, which carries deoxygenated blood).
2. Veins: Wider, thinner-walled vessels with valves to ensure blood flows toward the heart. They carry deoxygenated blood (except the pulmonary vein).
3. Capillaries: Tiny, one-cell-thick vessels that connect arteries and veins and allow material exchange with tissues.
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The Heart

The heart is a muscular organ that pumps blood. It is located in the chest cavity and protected by the ribs and sternum. It consists of four chambers: the left and right atria and the left and right ventricles. The septum divides the heart into two halves.

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Valves like the bicuspid and tricuspid prevent backflow of blood. The heart's contraction and relaxation cycles called heartbeats are powered by cardiac muscles.

Transport in Plants

Unicellular plants rely on diffusion for material exchange, while multicellular plants use vascular tissues for transportation. Plant sap, a fluid in vascular tissues, and cell sap in vacuoles help move substances.

Key Processes

• Water and Mineral Absorption: Water is absorbed via osmosis, and minerals are transported through xylem tissues.
• Translocation: Movement of food substances, like glucose, from leaves to other plant parts via the phloem.
• Transpiration: Loss of water vapor from leaves through stomata, lenticels, or the leaf cuticle. It helps draw water up from the roots.

Factors That Affect the Rate of Transpiration

1. Light: Increased light intensity raises the rate of photosynthesis, which generates heat and increases the rate of transpiration.
2. Humidity: Higher humidity slows down the rate of transpiration, while lower humidity speeds it up.
3. Stomatal Pores: When guard cells are flaccid, the stomata close, reducing transpiration. When guard cells are turgid, the stomata open, allowing transpiration to occur.
4. Wind: Faster wind speeds remove water vapor around leaves more quickly, leading to a higher rate of transpiration.
5. Soil Water: When soil water levels are high, plants absorb more water, which increases the rate of transpiration.

Importance of Transpiration to Plants

• Transpiration aids in the absorption of water and mineral salts from the soil.
• It helps in the movement of water within the plant.
• It provides water for various physiological processes within plant cells.