IB myp 4-5 Biology – Study notes- All Topics
Topic :Metabolism-Circulation
Topic :Metabolism– Weightage : 21 %
All Questions for Topic : Nutrition,Digestion,Biochemistry and enzymes,Movement and transport,Diffusion,Osmosis,Gas exchange,Circulation,Transpiration and Translocation,Homeostasis
Human Circulatory System
What Is the Circulatory System?
The human circulatory system is the body’s internal transport network. It delivers oxygen, nutrients, and hormones to all body cells and carries away wastes like carbon dioxide and urea.
It Includes:
- Heart – the pumping station
- Blood vessels – the pipelines
- Blood – the transport fluid
Main Functions:
- Transport of oxygen and nutrients to body cells
- Removal of carbon dioxide and waste products
- Circulation of hormones from glands to target organs
- Helps regulate body temperature
- Supports the immune system
Double Circulation in Humans
Humans have two circulation loops:
1. Pulmonary Circulation
- Carries deoxygenated blood from the heart to the lungs
- Returns oxygenated blood to the heart
2. Systemic Circulation
- Sends oxygenated blood to the body
- Returns deoxygenated blood to the heart
Structure and Function of the Heart
Feature | Description |
---|---|
Chambers | 4 – two atria (top), two ventricles (bottom) |
Valves | Prevent backflow (tricuspid, bicuspid, semilunar) |
Right Side | Pumps deoxygenated blood to the lungs |
Left Side | Pumps oxygenated blood to the rest of the body |
Pacemaker (SA node) | Controls heartbeat rhythm |
Heartbeat | Caused by muscle contraction, creates pulse |
Blood Flow Path:
- Body → Right Atrium (via vena cava)
- Right Atrium → Right Ventricle
- Right Ventricle → Lungs (via pulmonary artery)
- Lungs → Left Atrium (via pulmonary veins)
- Left Atrium → Left Ventricle
- Left Ventricle → Body (via aorta)
Types of Blood Vessels
Type | Function | Structure |
---|---|---|
Arteries | Carry blood away from the heart | Thick muscular walls, small lumen, no valves |
Veins | Carry blood to the heart | Thin walls, large lumen, valves to prevent backflow |
Capillaries | Allow exchange between blood and tissues | Very thin (1 cell thick), tiny and branched |
Blood Components & Their Roles
Component | Function |
---|---|
Red Blood Cells (RBCs) | Carry oxygen using hemoglobin |
White Blood Cells (WBCs) | Defend against infections |
Platelets | Help in blood clotting |
Plasma | Transports nutrients, hormones, CO₂, and wastes |
Oxygen Transport & High Altitude
Role of RBCs and Hemoglobin:
- Hemoglobin binds to oxygen in the lungs and releases it in body tissues
- More RBCs = better oxygen delivery
Effect of High Altitude:
- Less oxygen in the air
- Body responds by:
- Increasing heart rate
- Producing more hemoglobin
- Reducing oxygen saturation
Cardiovascular Diseases
- Atherosclerosis: Fatty deposits narrow the arteries
- High cholesterol: Increases blockage risk
- Smoking, high blood pressure, lack of exercise
Treatments
Intervention | Description |
---|---|
Angioplasty | Balloon used to open blocked arteries |
Stents | Mesh tube keeps arteries open |
Statins | Drugs that lower cholesterol levels |
Lifestyle & Heart Health
- Eat a balanced diet (low in saturated fats)
- Do regular exercise
- Avoid smoking
- Manage stress and check blood pressure
Public Responsibility:
- Health campaigns (anti-smoking ads)
- Health education
- Regular checkups
Key Features of the Circulatory System
- Closed system: Blood flows only in vessels
- Double circulation: Blood goes through heart twice
- Efficient: Delivers oxygen quickly
- Responsive: Adjusts to exercise and stress
Xylem and Phloem Transport in Plants
What Are Xylem and Phloem?
Plants have a transport system made up of two main tissues:
- Xylem – moves water and minerals from roots to leaves
- Phloem – moves sugars (food) made during photosynthesis from leaves to other parts of the plant
These two tissues work like highways inside the plant, helping it survive, grow, and stay healthy.
Xylem – Transport of Water and Minerals
Function:
Carries water and dissolved minerals from the roots to the stem and leaves
Key Features:
- Made up of dead, hollow cells joined end to end
- Forms long tubes with no end walls, allowing water to flow easily
- Lignin in the walls makes them strong and waterproof
- Transport is one-way only – from roots upwards
How It Works:
- Water enters the roots by osmosis
- Water moves up due to:
- Root pressure = pushing from below
- Capillary action = narrow tubes draw water up
- Transpiration pull = the main upward force
Phloem – Transport of Sugars (Translocation)
Function:
Carries glucose and other sugars from the leaves (where they are made) to the rest of the plant
Key Features:
- Made of living cells called sieve tube elements
- Sieve tubes have sieve plates at their ends
- Companion cells provide energy for transport
- Transport is two-way – up and down the plant
Process Name:
This movement of sugars is called translocation
Why Is Phloem Important?
- Supplies growing parts like buds and fruits
- Sends sugars to roots for storage
- Helps repair damaged parts of the plant
Differences Between Xylem and Phloem
Feature | Xylem | Phloem |
---|---|---|
Type of transport | Water and minerals | Sugars and other nutrients |
Direction | One-way (roots to leaves) | Two-way (depends on need) |
Cell type | Dead cells | Living cells |
Cell structure | Hollow tubes with thick walls | Sieve tubes with sieve plates |
Energy required | Passive (no energy used) | Active (needs energy) |
Why Is This Transport System Important?
- Helps plants grow taller and reach sunlight
- Keeps leaves firm by maintaining water pressure
- Supplies all plant parts with the substances they need
- Supports photosynthesis, growth, storage, and repair
Real-Life Example
If you cut a celery stalk and place it in colored water, the color moves up through the xylem. This shows how water travels inside the plant.
If the leaves are removed or damaged, less translocation happens – affecting growth in roots and fruits.
Transpiration Stream
What is Transpiration?
Transpiration is the loss of water vapor from plant leaves, mainly through tiny pores called stomata. It’s a natural process that:
- Helps pull water upward from roots
- Cools the plant
- Transports minerals
- Supports photosynthesis
Role of Stomata:
- Stomata are small openings on the underside of leaves.
- They allow carbon dioxide in and water vapor out.
- Guard cells control stomatal opening and closing.
- When open, water evaporates = transpiration happens!
What is the Transpiration Stream?
The transpiration stream is the continuous flow of water from roots → stem → leaves, driven by water loss from the leaves.
Step-by-Step Flow:
- Water uptake by roots (osmosis)
- Transport upward through xylem vessels
- Evaporation from leaf surface via stomata
- Transpirational pull creates upward suction
🌡️ Factors That Affect Transpiration
Factor | What It Does | Effect on Transpiration |
---|---|---|
Light | Opens stomata for photosynthesis | ⬆ Increases |
Wind | Removes humid air from leaf surface | ⬆ Increases |
Temperature | Speeds up evaporation | ⬆ Increases |
Humidity | Adds moisture to surrounding air | ⬇ Decreases |
How Do We Measure Transpiration?
We use a tool called a potometer – it measures the rate of water loss in plants.
Types of Potometers:
- Bubble Potometer: Tracks movement of air bubble to measure rate (e.g. cm/h)
- Mass Potometer: Measures weight loss – more accurate in sealed systems
Investigating Transpiration
Try These Experiments:
- Use a fan to vary wind speed
- Compare leaves of different surface areas
- Use sealed beakers to track water loss
- Change light intensity or temperature and record results
Hypothesis Example:
“If fan speed increases, the rate of transpiration will increase because wind removes water vapor faster from the leaf surface.”
Graph Interpretation Skills
- Plot transpiration rate vs. environmental factor
- Spot patterns (e.g., higher temp = faster loss)
- Compare control vs. test groups
- Suggest improvements (e.g., repeat trials, keep light constant)
Transpiration and Forest Ecosystems
Biotic Pump Hypothesis:
- Forests transpire large amounts of water
- Water vapor rises, cools, and forms clouds
- This pulls in moist air from oceans → causes rainfall
Case Study: Atlantic Forest
- Deforestation reduces transpiration
- Less water vapor = fewer clouds
- Rainfall drops, increasing risk of drought
Water Cycle in Forests:
- Water evaporates from leaves
- Rises and cools → forms clouds
- Clouds rain → repeats the cycle
Scientific Thinking Skills
Skill | Example Task |
---|---|
Designing a method | Set up a potometer with fan and thermometer |
Building a hypothesis | Predict how temperature affects bubble speed |
Interpreting graphs | Describe trends and reasons for results |
Evaluating methods | Suggest control variables and improvements |
Explaining forest impact | Link transpiration with rainfall patterns |
Key Points to Remember
- Transpiration: Water loss from leaves via stomata
- Transpiration Stream: Continuous water flow from root to leaf
- Xylem: Transports water upwards
- Potometers: Used to measure transpiration rate
- Environmental factors: Light, wind, humidity, and temperature affect transpiration
- Forests: Vital for rainfall due to transpiration
- Scientific skills: Design, predict, measure, evaluate, and explain