NCERT-Solutions-Class 7: Science: Transportation in Animals and Plants
NCERT notes along with solutions for class 7: science – Chapter “Transportation in Animals and Plants” are provided here. The notes as well as solutions are very helpful for the students to understand the topic. The solutions will be handy for quickly completing the homework and preparing for exams.
Circulatory System
Key Concept
The circulatory system is a network made up of blood, blood vessels (arteries, veins, and capillaries) and the heart that transports food, water, and oxygen to different parts of our bodies, as well as wastes to areas where they may be removed.- The circulatory system is also called the cardiovascular system.
- The word cardiovascular is made up by combining two words – Cardio means heart and vascular means blood vessels.
- The heart pumps blood into the vessels and the blood vessels circulate the blood throughout the body.
- The circulatory system consists of three main parts:-
1. Blood
2. Blood Vessels
3. Heart
Blood
Key Concept
Blood is a fluid that circulates in our body through blood vessels. Blood consists of red blood cells (RBC), white blood cells (WBC) and platelets floating in a liquid called plasma.
Red Blood Cells (RBC)
- Red Blood Cells or erythrocytes (erythro – Red & cytes – Cells) are tiny disc-like cells (bioconcave) and it does not have any nuclei.
- Red Blood cells are formed from stem cells of bone marrow.
- Red Blood Cells contain a red pigment called haemoglobin which makes blood appear red. Haemoglobin binds with oxygen in the lungs and transports it to every cell.
- RBC also transport carbon dioxide from the body`s cells to the lungs for exchange of gases.
- Each red cell lives for about 4 months (120 days), after which it breaks down.
White Blood Cells (WBC)
- White Blood Cells are also called leukocytes (leuko – White and cytes – Cells).
- White Blood Cells are made in the same bone marrow that makes red blood cells.
- White blood cells form part of the immune system that protects our body against both infectious diseases and foreign invaders.
WBC are of various types. These are categorized into two main groups –
1. Granulocytes
2. Agranulocytes
- Granulocytes – Granulocytes include neutrophils, eosinophils, and basophils.
- Agranulocytes – Agranulocytes include the monocytes and lymphocytes.
Platelets (Thrombocytes)
- Platelets are small, colourless fragments of cells that help in clotting of blood.
- Platelets are made in the bone marrow.
- The platelets collect at a wound site in conjunction with other clotting factors, such as fibrinogen, to form a fibrin clot that prevents blood loss and allows the wound to heal.
Plasma
- The liquid component of blood is called plasma.
- Plasma contains coagulation factors and antibodies.
- Proteins such as fibrinogen, albumin and globulins make up an important part of the plasma.
- Fibrinogen is needed for clotting.
- Albumin transports hormones and fatty acids, buffers pH and maintains osmotic pressures.
- Globulin proteins include antibodies, which combat bacteria and other foreign matter.
- The plasma also contains amino acids, glucose and lipids (fats).
Blood Vessels
- Blood vessels are tubular structures that carry blood throughout the body.
- There are three main types of blood vessels:
- arteries
- veins
- capillaries.
Arteries
Arteries (Pic on the right side/ credit-NCERT Textbook) are fairly wide vessels that carry oxygenated blood (oxygen rich blood), from the heart to the various parts of the body except for pulmonary arteries which carry deoxygenated blood (Carbon dioxide rich blood) from the heart to the lungs.- Arteries have elastic tissue and muscle fibres in their thick walls.
- The arteries divide into smaller vessels called arterioles.
- The arterioles divide repeatedly to form a branching network of microscopic vessels passing between the cells of every living tissue. These final branches are called capillaries.
Veins
Veins (Pic on the right side/ Credit-NCERT Textbook) are the vessels that carry carbon dioxide-rich blood, except pulmonary veins, from all parts of the body back to the heart. - The veins have thin walls, less elastic and less muscular than those of the arteries.
- The blood pressure in veins is steady and is less than that in the arteries.
- Veins have valves that allow blood to flow only in one direction i.e. towards the heart.
Capillaries
Capillaries (Pic on the right side/ Credit-NCERT Textbook) are the smallest blood vessels in the body. - It connects arterioles (small arteries) to venules (small veins).
- The primary function of capillaries is to enable the exchange of oxygen, nutrients, carbon dioxide, and waste products between the blood and surrounding tissues.
Differences between Artery and Veins
| Arteries | Veins |
| It supplies oxygenated blood from heart to different parts of the body except pulmonary artery. | It transport deoxygenated blood from different parts of the body to the heart except pulmonary veins. |
| It has a narrow lumen | It has a wide lumen |
| Blood is under high pressure | Blood is under low pressure |
| It does not have valves as the blood flows in a single direction due to the pumping of the heart. | It has valves to prevent flowing blood from backward flowing. |
Heart
Key Concept
Heart is a pumping organ that pumps blood into the blood vessels so that it can reach every parts of the body. Heart is made up of cardiac muscles.
Location of Human Heart: Our heart is situated in the thoracic cavity, in between the two lungs, slightly tilted to the left.
Size of the Human Heart – Human heart is about the size of a clenched fist.
Structure of the Human Heart
- Our heart (Pic on the right side- credit: NCERT Textbook) contains four chambers: two small upper chambers called atria (single Atrium) and two bigger lower chambers called ventricles.
- The right and left atria are separated by a thin, muscular wall known as the interatrial septum, while the left and right ventricles are separated by a thicker wall known as the interventricular septum.
- The atrio-ventricular septum is a thick fibrous structure that separates the atrium and ventricles on the same side. However, each of these septa has an entrance that connects two chambers on the same side.
- The tricuspid valve, made up of three muscular flaps or cusps, guards the opening between the right atrium and right ventricle. The left atrium and left ventricle are guarded by a bicuspid or mitral valve.
- The openings of the right and the left ventricles into the pulmonary artery and the aorta respectively are provided with the semilunar valves.
- The valves in the heart allows the flow of blood only in one direction, i.e., from the atria to the ventricles and from the ventricles to the pulmonary artery or aorta. These valves prevent any backward flow.
Do You Know?
Humans have a double circulatory system, which means the blood passes through the heart twice on each loop around the body. It travels from the heart to the lungs, from the lungs to the heart and from the heart to the rest of the body before returning to the heart.Flow of blood through heart
Do You Know?
Animals such as sponges and Hydra do not possess any circulatory system. The water in which they live brings food and oxygen as it enters their bodies. The water carries away waste materials and carbon dioxide as it moves out. Thus, these animals do not need a circulatory fluid like the blood.
Blood Pressure
When the heart contracts it pushes blood into blood vessels which creates blood pressure.
A blood pressure reading consists of two values:
• Systolic value – blood pressure while the heart is squeezing.
• Diastolic value – blood pressure while the heart is relaxing.
The average blood pressure for an adult is 120/80 mmHg. The first number is the systolic value and the second number is the diastolic value.
Heartbeat
- One complete contraction (systole) and relaxation (diastole) of the atrium and ventricles of the heart constitute a heartbeat.
- The heart normally beats 72 – 75 times per minute.
- A stethoscope is used to hear the sound of the heartbeat.
- The volume of blood pumped out of the heart with every beat is 0.07 litres.
Stethoscope
Stethoscope is a device used by doctors to amplify the sound of the heart. It consists of a chest piece that carries a sensitive diaphragm, two ear pieces and a tube joining the parts. Doctors can get clues about the condition of your heart by listening through a stethoscope.
In order to hear the sound within the body, either the diaphragm or bell can be used.
1. Closed diaphragm – High frequency lung sounds.
2. Open bell – low frequency heart sounds.
Excretion in Animals
- When our cells perform their functions, certain waste products are released. These are toxic and hence need to be removed from the body.
- For example – Urea is a toxic substance produced in the liver. Urea is removed from the body by the kidneys.
- The process of removal of wastes produced in the cells of the living organisms is called excretion. The parts involved i.e. kidneys, ureters, bladders and urethra in excretion form the excretory system.
Do You Know?
- An adult human normally passes about 1 -1.8 l of urine in 24 hrs.
- The urine consists of 95% of water, 2.5% of urea and 2.5 % other waste products.
Excretory system in humans
In humans the excretory system involves one pair of kidneys, one pair of ureters, a urinary bladder and a urethra.
How the wastes remove from the blood?
Kidneys play a vital role in removing waste products from the blood by filtering out the waste materials i.e. urea. Alongwith urea, the kidneys also remove excess water and ions from the blood in the form of urine.
Kidneys filter blood in a three-step process.
1. Filtration – filtration is carried out in Glomerules (a part of nephron). As the blood flows through glomerules, almost all constituents of plasma pass through it except plasma protein. The filtrate mainly consists of water with dissolved salts, glucose, urea and uric acid.
2. Reabsorption – The filtrate from the glomerules now collects in the renal capsule (Bowman`s Capsule) and trickle down in the renal tubule. As it does so, the capillaries that surround the renal tubule absorb back into the blood those substances which the body needs. First, all the glucose is reabsorbed, with much of the water. Then some of the salts are taken back to keep the correct concentration in the blood.
3. Secretion -Salts not needed by the body are left to pass on down the kidney tubule together with the urea and uric acid. So, these nitrogenous waste products, excess salts and water continue down the renal tube into the pelvis of the kidney. From here the fluid, now called urine, passes down the ureter to the urinary bladder and is then removed from the body through urethra.
Transport of substances in plants
- The transportation system in plants mainly involves transport of water, minerals and food throughout the plant.
- Plants transport these things through a special kind of tissue called Vascular tissue.
- Vascular tissue is a complex tissue formed from two or more cells mainly Xylem and Phloem.
Xylem
- It is a vascular tissue that is responsible for transportation of water and minerals from the roots to the leaves of the plants.
- The flow of water is unidirectional and in the upward direction.
- Xylem contains dead cells arranged end to end forming continuous vessels.
- Xylem have a hollow central space or lumen through which the water passes.
- Xylem is composed of four basic types of cells (tracheid, vessel, xylem fibre and xylem parenchyma).
Phloem
- It is responsible for the transportation of food/ glucose from the leaves to other parts of the plants.
- The transportation is bi-directional i.e. both in the upward and downward direction.
- The Phloem consists of living cells (except phloem fibre) at all stages of development.
- Phloem is composed of four basic types cells – sieve tubes, companion cells, phloem fibre and phloem parenchyma.
- How water and nutrients absorbed by the roots are transported to the leaves?
Principle
- Water moves from an area of higher total water potential to an area of lower total water potential.
- Transpiration creates negative pressure (tension) at the leaf surface. This tension helps Xylem to pull up water from the roots and transport it to the leaves of the plant.
- Plant root hairs pass between soil particles to reach soil water. The soil water has a greater water potential than the inside of the root hair cell. This allows water to enter the root hair cells via osmosis (Osmosis-movement of water/ other solutes from higher concentration to lower concentration region). Water from the root hair cell goes into the root cortex, which is the root’s outer layer. Continuing in this manner, a gradient of water potential is established throughout the root cortex. Xylem takes up the water along with minerals from the root and transports it to the leaves.
Solution of the exercise
1. Match structures given in Column I with functions given in Column II.
| Column I | Column II |
|---|---|
| (i) Stomata | (a) Absorption of water |
| (ii) xylem | (b) Transpiration |
| (iii) Root hairs | (c) Transport of food |
| (iv) Phloem | (d) transport of water |
| —–. | (e) Synthesis of carbohydrates |
| Column I | Column II |
|---|---|
| (i) Stomata | (b) Transpiration |
| (ii) xylem | (d) Transport of water |
| (iii) Root hairs | (a) Absorption of water |
| (iv) Phloem | (c) transport of food |
2. Fill in the blanks.
(i) The blood from the heart is transported to all parts of the body by the ………….
(ii) Haemoglobin is present in ………………………………cells.
(iii) Arteries and veins are joined by a network of ……………………………
(iv)The rhythmic expansion and contraction of the heart is called…………………………………
(v)The main excretory product in human beings is …………………………………
(vi) Sweat contains water and ………………………………………
(vii)Kidneys eliminate the waste materials in the liquid form called…………………………………
(viii) Water reaches great heights in the trees because of suction pull caused by ………………………
Sol:
(i) Arteries
(ii) Red blood
(iii) Capillaries
(iv) Heartbeat
(v) Urea
(vi) Salts
(vii) Urine
(viii) transpiration
3. Choose the correct option:
(i) xylem
(ii) phloem
(iii) stomata
(iv) root hair
(i) in the shade
(ii) in dim light
(iii) under the fan
(iv) covered with a polythene bag
(a) (i) Xylem
(b) (iii) under the fan
4. Why is transport of materials necessary in a plant or in an animal? Explain.
Transport of materials is necessary in plants and animals because:
- Every cell of plants and animals needs a regular supply of nutrients and oxygen to release energy through respiration.
- Waste products generated by cells need to be transported to the excretory organs because the accumulation of these waste products causes harmful effects on the organism’s body.
5. What will happen if there are no platelets in the blood?
Platelets are responsible for clotting of blood. If there are no platelets, the blood will not clot in the event of injury. This will result in enormous loss of blood from the body and ultimately death.
6. What are stomata? Give two functions of stomata.
Stomata are tiny pores that are present on the surface of leaves. The two main functions of stomata are:
- Stomata helps in the exchange of gases (carbon dioxide and oxygen).
- Evaporation of water through leaves occurs due to stomata.
7. Does transpiration serve any useful function in the plants? Explain.
Transpiration serves a very useful function in plants.
- It creates a suction pull which transfers water to a great height.
- Transpiration also helps to cool the plant due to evaporation of water.
8. What are the components of blood?
The main components of blood are:
- Plasma
- Red blood cells
- White blood cells
- Platelets
9. Why is blood needed by all the parts of a body?
Blood is needed by all parts of the body because it is one of the important components of the transportation system of our body. It performs the following important functions:
- It transports food, water and oxygen to every cell of our body.
- It transports wastes to parts from where they can be removed.
- It helps in maintaining the heat of our body.
- It carries RBC which protects our body from germs.
10. What makes the blood look red?
Red Blood Cells contain a red pigment called haemoglobin which makes blood appear red.
11. Describe the function of the heart.
The heart plays many functions in the body. The main functions of the heart are:
- The heart is a pumping organ that pumps oxygenated blood throughout the body.
- The heart receives deoxygenated blood from the body and sends it to the lungs for oxygenation.
- The heart helps in maintaining blood pressure.
- The heart also helps in sending hormones and nutrients to different parts of the body.
12. Why is it necessary to excrete waste products?
The cells of our body produce some waste products like Urea which are toxic in nature. If not excreted out from the body, it can cause damage to cells and hence prove fatal. Therefore, it is necessary to excrete out waste products from our body.
13. Draw a diagram of the human excretory system and label the various parts.
In humans the excretory system involves one pair of kidneys, one pair of ureters, a urinary bladder and a urethra.