Transportation in Animals and Plants
"'A city needs roads to transport goods. A body needs CIRCULATORY and VASCULAR systems to transport substances to every cell.'"
1. Need for Transportation
In SINGLE-CELLED organisms (Amoeba), substances diffuse directly through the cell membrane. In MULTI-CELLULAR organisms (humans, trees), diffusion is too SLOW — a specialised TRANSPORT system is needed.
What needs to be transported:
- Oxygen → to all cells for respiration
- Nutrients (glucose, amino acids) → from digestive system to cells
- Hormones → chemical messengers
- Waste products (CO₂, urea) → to excretory organs
- Water and minerals (in plants) → from roots to leaves
2. The Circulatory System in Humans
'The heart is a MUSCULAR PUMP that beats continuously. Together with BLOOD VESSELS and BLOOD, it forms the CIRCULATORY SYSTEM.'
Components
| Component | Description | Function |
|---|---|---|
| Heart | Muscular organ (size of a fist) | PUMPS blood throughout the body |
| Blood | Fluid connective tissue | CARRIES oxygen, nutrients, waste |
| Blood vessels | Arteries, veins, capillaries | PATHWAYS for blood flow |
Blood — The Transport Fluid
| Component | % of Blood | Function |
|---|---|---|
| Plasma | 55% | Liquid part. Carries dissolved nutrients, hormones, waste |
| Red blood cells (RBCs) | 44% | CONTAIN HAEMOGLOBIN (iron-rich) that BINDS oxygen. Give blood its RED colour. |
| White blood cells (WBCs) | <1% | FIGHT infections. Part of the immune system. |
| Platelets | <1% | CLOT blood at injury sites to PREVENT bleeding |
Haemoglobin: 'The iron-containing protein in RBCs that BINDS to oxygen in the lungs and RELEASES it in the tissues. This is why blood is RED — oxyhaemoglobin is bright red, deoxyhaemoglobin is dark red.'
Blood Vessels
| Vessel | Direction of Flow | Wall Thickness | Valves? | Pulse? |
|---|---|---|---|---|
| Arteries | AWAY from heart | Thick, elastic | NO | YES |
| Veins | TOWARD heart | Thin | YES | NO |
| Capillaries | Between arteries and veins | ONE cell thick | NO | NO |
Pulse: 'The EXPANSION and CONTRACTION of an artery WALL due to the surge of blood with each heartbeat. You can feel it at the WRIST (radial artery) or NECK (carotid artery).'
The Heart
Structure: Four chambers:
- Upper chambers: RIGHT ATRIUM and LEFT ATRIUM (receive blood)
- Lower chambers: RIGHT VENTRICLE and LEFT VENTRICLE (pump blood out)
Heartbeat:
- Deoxygenated blood from body → Right atrium → Right ventricle → → LUNGS (for oxygenation)
- Oxygenated blood from lungs → Left atrium → Left ventricle → → BODY
'The left ventricle has the THICKEST wall because it must pump blood to the ENTIRE body — it is the strongest chamber.'
Heartbeat rate: 'About 72-80 beats per minute at rest. Children have FASTER heart rates (90-100 bpm). The heart beats about 100,000 times PER DAY!'
Double Circulation
| Circuit | Path | Function |
|---|---|---|
| Pulmonary circulation | Heart → Lungs → Heart | Oxygenates blood, removes CO₂ |
| Systemic circulation | Heart → Body → Heart | Delivers O₂ and nutrients, collects waste |
3. Excretion in Humans
Excretion: The removal of NITROGENOUS waste products from the body.
Main organs:
| Organ | Waste Removed |
|---|---|
| Kidneys | Urea, excess water, salts (as URINE) |
| Lungs | Carbon dioxide |
| Skin | Excess water and salts (as SWEAT) |
| Liver | Breaks down haemoglobin → bile pigments |
The Excretory System
Kidneys: Two bean-shaped organs in the lower back. Each kidney contains about 1 MILLION filtering units called nephrons.
Path of urine: Kidneys → Ureters → Urinary bladder → Urethra
Function of kidneys:
- FILTER blood (remove urea, excess water, salts)
- REABSORB useful substances (glucose, some water, minerals)
- Form URINE for excretion
AP Context: 'In the hot summer months of AP (March-May), people sweat MORE. Drinking adequate water is essential to keep the kidneys functioning and prevent dehydration and kidney stones.'
Dialysis — Artificial Kidney
'When kidneys FAIL, a DIALYSIS machine filters the blood. Blood is passed through a machine that removes waste and excess water, and the clean blood is returned to the body.'
4. Transportation in Plants
'Plants need to transport WATER and MINERALS from roots to leaves, and FOOD from leaves to the rest of the plant.'
Xylem — Water and Mineral Transport
Xylem: Tubes of dead cells that form CONTINUOUS columns from roots to leaves.
Direction: ROOTS → UPWARD to STEMS → LEAVES.
How water rises: Three forces work together:
- Transpiration pull — water EVAPORATES from leaves through stomata, creating a SUCTION that pulls water up from the roots.
- Root pressure — roots push water up (minor force).
- Capillary action — water climbs narrow tubes.
'Transpiration is the LOSS of water vapour from plant leaves. It acts like a STRAW — as water evaporates from the top, more water is pulled up from below.'
Phloem — Food Transport
Phloem: Tubes of LIVING cells that transport food (glucose) from leaves to all parts of the plant.
Direction: LEAVES (source) → ALL parts of the plant (roots, stems, fruits, growing tips).
Translocation: The movement of FOOD through phloem. 'Sucrose (table sugar) is the main form of transported food. The food is used for ENERGY (respiration) or stored (as starch in roots, fruits, seeds).'
Comparison: Xylem vs Phloem
| Feature | Xylem | Phloem |
|---|---|---|
| What it transports | Water and MINERALS | FOOD (sucrose) |
| Direction | Upward (roots → leaves) | UP and DOWN (leaves → all parts) |
| Cells | DEAD cells (at maturity) | LIVING cells |
| Driving force | Transpiration pull | Energy-requiring process |
| Found in | Roots, stems, leaves | Roots, stems, leaves |
5. Common Mistakes and Fixes
| Mistake | Why It Is Wrong | Correct Approach |
|---|---|---|
| Arteries carry ONLY oxygenated blood | Pulmonary artery carries DEOXYGENATED blood to lungs | Arteries carry blood AWAY from heart — composition varies |
| All veins carry deoxygenated blood | Pulmonary vein carries OXYGENATED blood from lungs | Veins carry blood TOWARD the heart |
| Phloem carries water | Phloem carries FOOD, not water | XYLEM carries water; phloem carries food |
| Excretion and digestion waste are the same | Digestion waste (faeces) = UNDIGESTED food. Excretion waste (urine) = BODY's metabolic waste | They are DIFFERENT processes with different waste products |
| Heart pumps only oxygenated blood | Heart pumps BOTH oxygenated and deoxygenated blood (separate chambers) | The RIGHT side handles deoxygenated; the LEFT side handles oxygenated |
6. AP SSC Exam Focus
| Topic | Marks | Question Type |
|---|---|---|
| Heart structure and function | 3-4 | Label diagram, explain |
| Blood and blood vessels | 2-3 | Types, functions, differences |
| Excretory system | 2-3 | Parts, functions |
| Xylem and phloem | 3-4 | Compare, transport direction |
| Transpiration | 2-3 | Process and importance |
Quick Self-Test
Q1. Why do we need a transport system in our body? A1. Our body has millions of cells that need oxygen, nutrients, and waste removal. Diffusion is too slow — a circulatory system efficiently transports these substances.
Q2. Which blood vessel carries deoxygenated blood away from the heart? A2. The PULMONARY ARTERY carries deoxygenated blood from the heart to the lungs.
Q3. What is the function of haemoglobin? A3. Haemoglobin in red blood cells binds to oxygen in the lungs and releases it to body tissues.
Q4. What is transpiration and how does it help plants? A4. Transpiration is the loss of water vapour from leaves. It creates a SUCTION (transpiration pull) that draws water and minerals up from the roots through the xylem.
Q5. What is the difference between xylem and phloem? A5. Xylem transports water and minerals upward (roots → leaves). Phloem transports food (sucrose) from leaves to all parts of the plant.
Q6. Name the four chambers of the heart. A6. Right atrium, right ventricle, left atrium, left ventricle.
Q7. What is the role of platelets in blood? A7. Platelets help in BLOOD CLOTTING at the site of an injury, preventing excessive bleeding.
