Transportation in Animals and Plants 

Introduction

All living organisms require food, water, and oxygen to survive. These substances need to be transported to different parts of the body, and waste materials must be removed. This process is called transportation.

Circulatory System

In animals, the transportation of substances is carried out by the circulatory system, which consists of the heart, blood, and blood vessels. The heart pumps blood through the blood vessels to transport essential substances to body cells and carry wastes away for removal.

Blood

Blood is a red-coloured fluid that flows inside blood vessels. It performs several important functions:

1. Transports digested food from the small intestine to all parts of the body.

2. Carries oxygen from the lungs to body cells.

3. Transports waste materials to organs like kidneys for removal.

4. Protects the body from diseases.

Components of Blood

• Plasma: The liquid part of blood that carries food, water, salts, hormones, and waste materials.

• Red Blood Cells (RBCs): Contain haemoglobin, which binds with oxygen and carries it to all parts of the body. Gives blood its red colour.

• White Blood Cells (WBCs): Fight germs and protect the body from diseases.

• Platelets: Help in blood clotting. Platelets form a clot at the site of a cut to prevent excessive bleeding.

Blood Clotting

When the body is injured, blood flows out from the cut. Platelets gather at the wound and form a dark red clot, which stops the bleeding.

Blood Vessels

Blood vessels are tubes that carry blood throughout the body. During inhalation, fresh oxygen enters the lungs. This oxygen must be transported to all parts of the body. At the same time, blood picks up waste materials, including carbon dioxide, from the cells. Blood carrying waste returns to the heart and is then sent to the lungs for removal of carbon dioxide.

There are two main types of blood vessels: arteries and veins.

Arteries

• Carry oxygen-rich blood from the heart to all parts of the body.

• Blood flows at high pressure, so arteries have thick, elastic walls.

• Arteries branch into smaller vessels called capillaries, which reach the tissues.

Activity 11.1 – Pulse Rate:

1. Place your middle and index fingers on the inner side of your wrist.

2. Feel the throbbing movement. This is called the pulse and is due to blood flowing in the arteries.

3. Count the number of beats in one minute. This is your pulse rate.

4. A resting person usually has a pulse rate of 72–80 beats per minute.

5. You can also find pulse at other places like the neck or behind the knee.

6. Record your pulse rate and compare it with classmates.

Veins

• Carry carbon dioxide-rich blood from all parts of the body back to the heart.

• Have thin walls and valves to ensure blood flows only toward the heart.

• Capillaries join up to form veins, which eventually empty into the heart.

Capillaries

• Extremely thin blood vessels where exchange of substances occurs between blood and tissues.

• Connect arteries and veins to complete the circulation loop.

Heart

The heart is a vital organ that beats continuously, acting as a pump for the transport of blood. This blood carries oxygen, nutrients, and waste materials throughout the body. Despite working non-stop for years, the heart never stops pumping.

The heart is located in the chest cavity, with its lower tip slightly tilted towards the left. The size of the heart is roughly equal to the size of your fist.

To prevent mixing of oxygen-rich blood with carbon dioxide-rich blood, the heart has four chambers:

• Atria (singular: atrium): The two upper chambers

• Ventricles: The two lower chambers

A partition between the chambers ensures that oxygen-rich blood and carbon dioxide-rich blood remain separate.

Blood Flow through the Heart

• Blood from the body enters the right side of the heart and is pumped to the lungs.

• In the lungs, blood picks up oxygen and releases carbon dioxide.

• Oxygen-rich blood returns to the left side of the heart and is pumped to the rest of the body.

This continuous flow ensures that all body cells receive oxygen and nutrients while removing waste materials efficiently.

Heartbeat

The walls of the heart chambers are made of muscles. These muscles contract and relax rhythmically, and this rhythmic movement is called a heartbeat. Heartbeats continue every moment of our life. You can feel your heartbeat by placing your hand on the left side of your chest. Doctors use a stethoscope to listen to heartbeats. A stethoscope amplifies the sound of the heart and helps doctors assess the condition of the heart. It has a chest piece with a diaphragm, two ear pieces, and a connecting tube.

Activity 11.2 – Model Stethoscope:

1. Take a small funnel (6–7 cm diameter) and fix a rubber tube (50 cm long) on its stem.

2. Stretch a rubber sheet or balloon over the mouth of the funnel and secure it with a rubber band.

3. Place the open end of the tube on your ear and the mouth of the funnel on your chest near the heart.

4. Listen for the regular thumping sound – this is your heartbeat.

5. Count your heartbeat for one minute while resting and after running for 4–5 minutes. Record your pulse rate and heartbeat in a table and compare the results.

Key Point: Each heartbeat generates one pulse in the arteries. The pulse rate per minute indicates the rate of heartbeat. The rhythmic beating of the heart chambers maintains circulation and transport of substances throughout the body.

Special Note: Some animals, like sponges and Hydra, do not have a circulatory system. Water entering their bodies brings food and oxygen, and water leaving carries away wastes and carbon dioxide. These animals do not need blood or a circulatory fluid.

11.2 Excretion in Animals

Apart from carbon dioxide and undigested food, the body produces other waste materials that are harmful if they accumulate. These wastes are produced when cells perform their normal functions. Since these wastes are toxic, they need to be removed from the body.

The process of removing cellular wastes from the body is called excretion. The organs and structures that carry out this process form the excretory system.

• Excretion helps maintain internal balance in the body.

• Waste removal prevents toxicity and keeps the organism healthy.

• Examples of wastes: urea, salts, excess water, and other metabolic by-products.

Excretory System in Humans

The human body removes wastes present in the blood through the excretory system. This system filters blood, separating useful substances from harmful wastes.

Kidneys

• Blood reaches the two kidneys, which contain blood capillaries that filter the blood.

• Useful substances like glucose, salts, and water are reabsorbed into the blood.

• Wastes dissolved in water are removed as urine.

Urine Transport

• From the kidneys, urine flows through ureters into the urinary bladder.

• The bladder stores urine until it is released through the urethra at the urinary opening.

• An adult passes about 1–1.8 L of urine in 24 hours. Urine consists of roughly 95% water, 2.5% urea, and 2.5% other wastes.

Sweat

• Sweat is another way the body removes wastes like water and salts.

• During hot weather, white patches on clothes, especially underarms, are due to salts in sweat.

• Sweating also helps cool the body through evaporation, similar to how water cools in an earthen pot.

11.3 Transport of Substances in Plants

Plants absorb water and mineral nutrients from the soil through their roots. These substances are transported to the leaves, where photosynthesis occurs and food is prepared using water and carbon dioxide.

Food provides energy to every cell of the plant. Cells use this energy for vital life processes. Therefore, it is essential that the food prepared in the leaves reaches all parts of the plant, including those that cannot make food.

Transport of Water and Minerals in Plants

Plants absorb water and minerals from the soil through their roots. The roots have root hairs that increase the surface area for absorption. Root hairs are in contact with water present between soil particles.

Water and mineral nutrients move from the root to the leaves through a special transport system in plants. Plants have pipe-like vessels made of specialized cells forming the vascular tissue. Vascular tissue is a group of cells that perform a specialized function in an organism.

The vascular tissue responsible for transporting water and minerals is called the xylem. Xylem forms a continuous network of channels connecting the roots, stem, branches, and leaves, allowing water to reach the entire plant.

Leaves synthesize food, which needs to be transported to other parts of the plant. This is done by another vascular tissue called the phloem. Together, xylem and phloem transport water, nutrients, and food in plants.

Activity 11.3 – Observing Water Movement:

1. Take a large potato and peel off its outer skin.

2. Cut one end to make the base flat.

3. Make a deep, hollow cavity on the opposite side and fill half with sugar solution.

4. Mark the level of the solution using a pin in the potato wall.

5. Place the potato in a dish with a small amount of water, ensuring the water level is below the pin.

6. Leave it for a few hours.

Observation: The level of sugar solution increases. This shows that water moves from one cell to another over short distances, similar to how water moves from the soil into the xylem vessels in roots.

Transpiration in Plants

Plants absorb water and mineral nutrients from the soil, but not all the water is used for growth and photosynthesis. The excess water evaporates from the leaves through tiny pores called stomata. This process is called transpiration.

Keywords – Meanings

• Ammonia: A toxic nitrogenous waste produced by the breakdown of proteins.

• Artery: Blood vessel that carries oxygen-rich blood away from the heart to the body.

• Blood: Red fluid in the body that transports oxygen, food, and waste.

• Blood vessels: Tubes that carry blood throughout the body (arteries, veins, capillaries).

• Capillary: Tiny blood vessels where exchange of substances occurs between blood and tissues.

• Circulatory system: The system of heart, blood, and blood vessels that transports substances in the body.

• Dialysis: A medical process to filter blood when kidneys fail.

• Excretion: Process of removing waste products produced by cells.

• Excretory system: Organs that remove wastes from the body (kidneys, ureters, bladder, urethra).

• Haemoglobin: Red pigment in RBCs that carries oxygen.

• Heartbeat: The contraction and relaxation of heart muscles.

• Kidneys: Organs that filter blood to remove wastes and produce urine.

• Phloem: Plant tissue that transports food from leaves to other parts.

• Plasma: Liquid part of blood that carries food, water, hormones, and waste.

• Platelets: Blood cells that help in clotting to stop bleeding.

• Pulse: The throbbing of arteries caused by heartbeats; number of beats per minute.

• Red blood cell (RBC): Cell in blood that carries oxygen using haemoglobin.

• Root hair: Tiny hair-like structure on roots that absorbs water and minerals.

• Stethoscope: Instrument used to listen to heartbeats and breathing.

• Sweat: Liquid secreted by skin to remove water and salts and cool the body.

• Tissue: Group of cells performing a specific function.

• Urea: Nitrogenous waste formed in the liver and removed by kidneys.

• Ureter: Tube that carries urine from the kidney to the bladder.

• Urethra: Tube that carries urine out of the body from the bladder.

• Uric acid: Nitrogenous waste excreted in smaller animals and humans.

• Urinary bladder: Organ that stores urine until it is excreted.

• Vein: Blood vessel that carries carbon dioxide-rich blood to the heart.

• White blood cell (WBC): Blood cell that fights germs and infections.

• Xylem: Plant tissue that transports water and minerals from roots to leaves.

Exercises: Transportation and Excretion

1. Match the following

Answer Key (correct matching):

• Stomata → Transpiration

• Xylem → Transport of water

• Root hairs → Absorption of water

• Phloem → Transport of food
  
  

2. Fill in the blanks

1. The blood from the heart is transported to all parts of the body by the arteries.

2. Haemoglobin is present in red blood cells (RBCs).

3. Arteries and veins are joined by a network of capillaries.

4. The rhythmic expansion and contraction of the heart is called heartbeat.

5. The main excretory product in human beings is urea.

6. Sweat contains water and salts.

7. Kidneys eliminate the waste materials in the liquid form called urine.

8. Water reaches great heights in the trees because of suction pull caused by transpiration.
   
   

3. Choose the correct option

(a) In plants, water is transported through:

• (i) Xylem ✅

• (ii) Phloem

• (iii) Stomata

• (iv) Root hair
  
  

(b) Water absorption through roots can be increased by keeping the plants:

• (i) in the shade

• (ii) in dim light

• (iii) under the fan

• (iv) covered with a polythene bag ✅
  
  

4. Why is transport of materials necessary in a plant or in an animal?

• Transport ensures that oxygen, nutrients, and water reach every cell, and wastes are removed efficiently. Without transport, cells cannot survive.
  
  

5. What will happen if there are no platelets in the blood?

• Blood would not clot, and even small cuts could lead to excessive bleeding.
  
  

6. What are stomata? Give two functions of stomata.

• Stomata are tiny pores on leaves.

• Functions:

  1. Transpiration – release water

  2. Gas exchange – intake of carbon dioxide and release of oxygen
     
     

7. Does transpiration serve any useful function in plants? Explain.

• Yes. Transpiration helps in:

  • Pulling water from roots to leaves

  • Cooling the plant during hot weather
    
    

8. What are the components of blood?

• Plasma, red blood cells, white blood cells, platelets
  
  

9. Why is blood needed by all parts of the body?

• Blood carries oxygen, nutrients, and hormones to all cells and removes wastes.
  
  

10. What makes the blood look red?

• Presence of haemoglobin in red blood cells.
  
  

11. Describe the function of the heart.

• The heart pumps blood throughout the body. It maintains circulation, ensuring oxygen and nutrients reach all cells and wastes are removed.
  
  

12. Why is it necessary to excrete waste products?

• Wastes like urea and carbon dioxide are toxic. Excretion prevents poisoning and maintains internal balance.
  
  

13. Draw a diagram of the human excretory system and label the parts:

• Kidneys, ureters, urinary bladder, urethra
  
  

Extended Learning – Activities and Projects

1. Find out about blood groups and why they are important in blood transfusions.

Blood Groups and Their Importance in Blood Transfusions

Blood Groups:

• Blood is divided into different groups based on the presence or absence of certain antigens on the surface of red blood cells.

• The main blood group system is ABO, which has four types: A, B, AB, and O.

• Another important factor is the Rh factor, which can be positive (+) or negative (−).

Importance in Blood Transfusions:

• During a blood transfusion, blood from a donor is given to a patient.

• Matching blood groups is crucial because mismatched blood can cause clumping of RBCs and dangerous reactions.

• Example:

  • Type O blood is called a “universal donor” because it can be given to people of any ABO group.

  • Type AB blood is a “universal recipient” because people with AB blood can receive any ABO type.
    
    

2. Learn about ECG (Electrocardiogram) – a test used by doctors to check heart activity. You can visit a doctor or refer to reliable online sources, e.g., HowStuffWorks – ECG.

What is an ECG?

• An ECG is a test that measures the electrical activity of the heart.

• It helps doctors check if the heart is beating normally and if there are any heart problems.
  
  

How it works:

• Small electrodes are placed on the chest, arms, and legs.

• The electrodes detect electrical signals that trigger the heart to contract and pump blood.

• The signals are displayed on a screen or printed on paper as waves.
  
  

Why it is important:

• Detects heart rhythm problems (arrhythmia).

• Shows damage to the heart muscles after a heart attack.

• Helps monitor the effectiveness of heart medications.

Download the Goa Board Std 7 Science Part II Textbook PDF. Includes all lessons from the official syllabus.