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Biology · Class 9 · Chapter 9: Transport

8 min

Key points

Transport is the movement of substances from one place to another in living organisms
Plants have two main transport systems: Xylem (transports water and minerals upward) and Phloem (transports prepared food)
Transpiration is the loss of water in the form of water vapors from aerial parts of plants, mainly through stomata
Root pressure and transpiration pull are the two main forces responsible for water movement in plants
Blood is the main transport medium in humans consisting of plasma, RBCs, WBCs and platelets
Heart is a muscular organ with four chambers - two atria and two ventricles
Single circulation occurs in fish while double circulation occurs in mammals including humans
Arteries carry blood away from heart, veins carry blood toward heart, capillaries connect arteries and veins
Lymphatic system helps in drainage of tissue fluid and defense against diseases

Definitions

Transport: The movement of substances from one place to another in living organisms
Transpiration: The loss of water in the form of water vapors from aerial parts of plants, mainly through stomata
Root Pressure: The pressure developed in roots due to active absorption of water and minerals from soil
Blood: A liquid connective tissue that transports substances throughout the body
Lymph: A colorless fluid containing lymphocytes that bathes the tissues and drains through lymphatic vessels

Worked example

Define osmosis and explain how it occurs in plant cells. Also mention two factors that affect the rate of osmosis. (6 marks)

Osmosis is the movement of water molecules from a region of higher water potential to a region of lower water potential through a selectively permeable membrane. In plant cells, water moves through the cell membrane into the cell when the cell has lower water potential than the surrounding solution, causing the cell to become turgid. The process occurs due to the kinetic energy of water molecules. Two factors affecting rate of osmosis are: (1) Temperature - higher temperature increases kinetic energy and rate of osmosis (2) Concentration gradient - greater difference in water potential increases the rate of osmosis.

Common mistakes

Students confuse xylem and phloem functions - remember xylem carries water UP, phloem carries food
Writing veins carry oxygenated blood - remember veins carry deoxygenated blood except pulmonary vein
Forgetting to mention stomata when defining transpiration
Confusing single and double circulation - fish have single, mammals have double
Not drawing proper labels in heart diagram - always label all 4 chambers and major vessels

Quick recap

Transport is the movement of substances in living organisms through passive transport (diffusion, osmosis, facilitated diffusion - no energy needed) and active transport (requires ATP energy). Osmosis is water movement through selectively permeable membrane from high to low water potential. Transpiration is water loss from plant leaves through stomata, controlled by guard cells.

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