9th Class Biology Chapter 9 Notes cover Unit 9 “Transport” from the Punjab Board syllabus. This chapter explains how materials move within plants and humans, including water transport, transpiration, blood composition, and the human circulatory system. These notes help matric students revise the chapter quickly with clear, exam-focused answers.
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Transport is one of the longest chapters in 9th Class Biology, so breaking it into plant transport and human transport makes revision much easier.
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Why Transport Is Necessary
In unicellular and simple organisms, diffusion works well because every cell is in direct contact with the environment. In complex multicellular bodies, cells are far apart from the environment, so a comprehensive transport system becomes necessary to move materials to and from cells.
9th Class Biology Chapter 9 Notes: Transport in Plants
Role and Absorption of Water
Water is vital for plant life because it is needed for:
- Photosynthesis
- Turgor (cell rigidity)
- Regulation of internal temperature
Land plants absorb water and minerals from soil through roots, transporting them to aerial parts via xylem. Vascular tissues (xylem and phloem) carry water and food throughout the plant body.
Structure and Function of Root Hairs
Root hairs are extensions of epidermal cells that provide a large surface area for absorption. Since root hair cytoplasm has a higher salt concentration than soil water, water enters by osmosis, while salts enter by diffusion or active transport.
What Is Transpiration?
Transpiration is the loss of water from the plant surface through evaporation. It mainly occurs through stomata, though some loss happens through the cuticle and lenticels.
Opening and closing of stomata depends on guard cells:
- When guard cells absorb water and become turgid, stomata open
- When guard cells lose water and become flaccid, stomata close
This process is controlled by potassium ion (K⁺) movement into guard cells, which draws in water and increases turgidity.
Factors Affecting Rate of Transpiration
Several factors influence how fast transpiration occurs:
- Light – higher light increases stomatal opening and transpiration rate
- Temperature – rate doubles with every 10°C rise, but very high heat (40-45°C) closes stomata
- Air humidity – dry air increases transpiration; humid air reduces it
- Air movement – wind increases evaporation from leaf surfaces
- Leaf surface area – more surface area means more stomata and more transpiration
Significance of Transpiration
Transpiration is called a “necessary evil” — it can cause wilting and death during drought, but it’s also essential because it:
- Creates transpirational pull for water and salt conduction
- Produces a cooling effect on the plant
- Allows gaseous exchange through wet leaf surfaces
Cohesion-Tension Theory
This theory explains how water rises to great heights in plants. As a leaf transpires, water moves from xylem to mesophyll cells, creating a pulling force called transpirational pull. This works because:
- Water is held in narrow xylem tubes
- Water molecules adhere to xylem walls (adhesion)
- Water molecules cohere to each other (cohesion)
Transport of Food (Pressure-Flow Mechanism)
Phloem transports food, mainly in the form of sucrose, in a two-way pressure-flow mechanism:
- Sources – exporting organs like mature leaves that produce sugar
- Sinks – areas of active growth or storage, like roots and developing fruits
At the source, sugar is actively loaded into sieve tubes, drawing water in by osmosis and creating pressure that pushes the solution toward the sink.
9th Class Biology Chapter 9 Notes: Transport in Humans
Human transport involves two systems: the blood circulatory system and the lymphatic system. Humans have a closed circulatory system, meaning blood never leaves the network of arteries, veins, and capillaries.
Composition of Blood
Blood is a specialized connective tissue made of plasma (55%) and blood cells (45%). An adult has about 5 litres of blood.
Plasma is 90-92% water and contains:
- Salts (mainly sodium chloride)
- Proteins (antibodies, fibrinogen, albumin)
- Digested food, hormones, and nitrogenous wastes
- Respiratory gases (O₂ and CO₂)
Types of Blood Cells
| Cell Type | Number (per mm³) | Function |
|---|---|---|
| Red Blood Cells (RBCs) | 5-5.5 million (male) | Transport O₂ and CO₂ via haemoglobin |
| White Blood Cells (WBCs) | 7000-8000 | Body defence against infection |
| Platelets | 250,000 | Blood clotting |
WBCs are divided into granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (monocytes, lymphocytes).
Blood Disorders
- Leukaemia – uncontrolled production of abnormal WBCs due to bone marrow mutation
- Thalassaemia – genetic defect in haemoglobin production, requiring regular blood transfusion
Blood Group Systems
ABO System: Discovered by Karl Landsteiner in 1900, based on antigens A and B on RBC surfaces:
- Blood group A – has antigen A
- Blood group B – has antigen B
- Blood group AB – has both antigens (universal recipient)
- Blood group O – has no antigens (universal donor)
Rh System: Based on Rh factor presence (Rh positive) or absence (Rh negative) on RBCs.
The Human Heart – 9th Class Biology Chapter 9 Notes
Structure of the Heart
The heart is a muscular pumping organ located between the lungs, enclosed in a protective sac called the pericardium. It has four chambers:
- Right and left atria – upper thin-walled chambers
- Right and left ventricles – lower thick-walled chambers (left ventricle is the strongest)
The Heart as a Double Pump
The heart receives deoxygenated blood from the body and pumps it to the lungs, while simultaneously receiving oxygenated blood from the lungs and pumping it to the whole body. Valves prevent backflow:
- Tricuspid valve – between right atrium and right ventricle
- Bicuspid valve – between left atrium and left ventricle
- Semilunar valves – at the base of pulmonary trunk and aorta
Cardiac Cycle and Heartbeat
One complete cardiac cycle includes:
- Cardiac diastole – chambers relax and fill with blood
- Atrial systole – atria contract, pushing blood to ventricles
- Ventricular systole – ventricles contract, pumping blood to lungs and body
The “lubb-dubb” sound comes from valves closing during these phases. Normal heart rate is about 70-75 beats per minute.
Blood Vessels
| Vessel | Function | Structure |
|---|---|---|
| Arteries | Carry blood away from heart | Thick, elastic walls |
| Veins | Carry blood toward heart | Thinner walls, have valves |
| Capillaries | Exchange materials | Single-cell thick walls |
Pulmonary and Systemic Circulation
- Pulmonary circulation – carries deoxygenated blood from heart to lungs and oxygenated blood back
- Systemic circulation – carries oxygenated blood from heart to body tissues and deoxygenated blood back
Cardiovascular Disorders
Common cardiovascular disorders include:
- Atherosclerosis – narrowing of arteries due to fatty deposits (plaques)
- Arteriosclerosis – hardening of arteries due to calcium deposits
- Myocardial infarction (heart attack) – blood supply interruption causing tissue death, with symptoms like severe chest pain radiating to the arm or jaw
Major risk factors include high cholesterol, hypertension, smoking, obesity, and a sedentary lifestyle.
FAQs
Q1. What topics are covered in 9th Class Biology Chapter 9 Notes?
9th Class Biology Chapter 9 Notes cover Transport, including water and food movement in plants, transpiration, cohesion-tension theory, blood composition, blood groups, and the structure and function of the human heart.
Q2. What is transpiration and why is it important?
Transpiration is the loss of water from plant surfaces through evaporation, mainly via stomata. It’s important because it creates transpirational pull, which draws water and minerals upward from roots to the rest of the plant.
Q3. What is the difference between arteries and veins?
Arteries carry blood away from the heart under high pressure with thick elastic walls, while veins carry blood toward the heart under low pressure and contain valves to prevent the backflow of blood.
Q4. Who is a universal blood donor and universal recipient?
People with blood group O are universal donors because their RBCs have no antigens, so they can donate to any blood group. People with blood group AB are universal recipients since they can receive blood from any group.
Q5. What causes a heart attack (myocardial infarction)?
A heart attack occurs when blood supply to part of the heart muscle is interrupted, usually due to a blood clot in the coronary arteries. This leads to tissue death and is often marked by severe chest pain.
Q6. What is the cohesion-tension theory in plants?
The cohesion-tension theory explains how water rises in plants. Transpiration creates a pulling force called transpirational pull, and cohesion between water molecules along with adhesion to xylem walls allows continuous water columns to move upward.