Transportation in Animals and Plants NCERT Solutions - Class 7 Science

1. Match structures in Column I with functions given in Column II.

Ans: 

(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. 

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

Ans: Arteries

2. Haemoglobin is present in _________ cells. 

Ans: Red blood

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

Ans: Capillaries

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

Ans: Heartbeat

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

Ans: Urea

6. Sweat contains water and _________. 

Ans: Salts

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

Ans: Urine

8. The water reaches great heights in the trees because of suction pull caused by _________. 

Ans: Transpiration

3. Choose the correct option:

1. In plants, water is transported through 

1. xylem 

2. phloem 

3. stomata 

4. root hair

Ans: (i) xylem

Xylem is a type of vascular tissue in plants that helps in the transport of water along with the dissolved nutrients from roots to other parts of the plant.

2. Water absorption through roots can be increased by keeping the plants 

1. in the shade 

2. in dim light 

3. under the fan 

4. covered with a polythene bag 

Ans: (iii) under the fan 

By placing the plants under a fan, there is an increase in the loss of water by transpiration, which in turn increases the rate of absorption of water through the roots.

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

Ans: 

• The transport of materials is important in a plant or in an animal, because their cells, which is the basic unit of life, require a constant supply of nutrients, oxygen, and water for the production of energy and its release during respiration. The cells need nutrients and oxygen for their metabolic processes. 

• Also, transportation is needed to carry away the waste products produced by the cells due to their metabolic activities. 

• Thus without transportation, the cells will neither receive the nutrients and oxygen nor be able to remove their metabolic wastes.

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

Ans: The main role of platelets in our body is to help in the clotting of blood that helps to stop any bleeding. Without platelets, clotting will not occur. Thus, if an injury or a cut happens on the body, without platelets to form a clot, there will be severe blood loss due to excessive bleeding, which can also result in death.

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

Ans: Stomata are the tiny openings in the surface of plants, found mainly on the lower surface leaves, and are also sometimes found on the plant stems too. Stomata are pores surrounded by specialized parenchymal cells, called guard cells that are used to control the gas exchange with the change in environmental conditions.

Stomata have two main functions:

• They help in gas exchange for the processes of respiration and photosynthesis.

• They also help in regulating water movement through transpiration. 

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

Ans: 

• Transpiration is the movement of water through a plant and its evaporation from leaves. Simply put, it is the loss of water from a plant in the form of water vapour. Thus transpiration serves a very useful function in plants.

• This loss of water from the aerial parts of the plant creates a ‘transpiration pull’ that helps in the rise of water absorbed by the roots to higher parts of the plant. 

• Another useful function of transpiration is helping in the cooling effect of plants, preventing drying out in the hot sun. 

8. What are the components of blood? 

Ans: Blood has two parts:

1. Fluid part – Plasma, which is majorly composed of water and contains chemicals, proteins, enzymes, salts, and gases dissolved in it.

2. Cellular part – RBC, WBC, and platelets.

1. RBCs – Red Blood Cells, which are responsible for carrying oxygen and carbon dioxide with the help of haemoglobin to and from the cells.

2. WBCs – White Blood Cells, which are a part of the immune system and maintain the immune response.

3. Platelets are responsible for the clotting of blood.

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

Ans: 

• Blood is a connective tissue that connects all parts of the body. 

• Blood helps to carry oxygen from the lungs to the cells and carbon dioxide produced by the cells is carried away from them to the lungs. 

• It also helps to carry nutrients to various parts of the body for their absorption. 

• Blood contains plasma that helps in clotting. It also helps in maintaining body temperature.

• WBCs that are responsible for the immune response are present in the blood, which helps us fight against diseases.

• Blood is also involved in the transport of hormones and the waste materials produced by the cells.

10. What makes the blood look red? 

Ans: Blood appears red due to the presence of a pigment called haemoglobin, in the red blood cells. Hemoglobin is a protein complex containing iron that helps in the transport of oxygen in the human body. Iron is found abundant in our blood, which tends to reflect red light, making the blood look red. Thus we can say that hemoglobin makes the blood look red.

11. Describe the function of the heart. 

Ans: 

• The heart is said to be a vital organ in our body, which functions as a pump, pumping blood throughout the body. 

• The heart is a part of the human circulatory system through which it pumps blood to transport nutrients, hormones, and oxygen to the cells via systemic circulation, and transports away carbon dioxide and other waste materials produced by the cells for their elimination.

• The heart pumps oxygenated blood from the lungs to organs and deoxygenated blood from the organs to the lungs for gas exchange. 

• The heart also maintains blood pressure.

12. Why is it necessary to excrete waste products? 

Ans: Waste products are produced as a result of metabolic processes in the cells, and they tend to be toxic. If they are not excreted, it will result in their buildup and accumulation in the cells that can result in toxicity and cause damage to cells and organs by preventing them from functioning normally. Thus we need to eliminate these waste products from our body by the process of excretion, with the help of kidneys.

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

Ans:

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Chapter 11 – Transportation in Animals and Plants

NCERT Solutions for Class 7 Science Chapters

11.1 Circulatory System

We all know that blood flows out whenever we get a cut. Blood is defined as the fluid that flows through the blood vessels. It transports oxygen from the lungs to various parts of the body. It also transports digested food from the alimentary canal (small intestine) to other parts. It is also the means of transport of waste material from different parts of the body to the excretory system. Blood contains several types of cells. The fluid component of blood is called plasma.

Amongst the different types of cells present in the blood, red blood cells (RBCs) form the major part. RBC contains hemoglobin, which imparts the red colour to the blood. The main function of hemoglobin is to bind and transfer oxygen to different parts of the body. Without hemoglobin, oxygen will not be transported efficiently.

Blood also contains white blood cells. The main function of the white blood cells is to maintain immunity against germs and pathogens that can enter our bodies by various means.

Even after getting cut, you will observe that the blood flow is stopped after a few minutes, and a blood clot is formed at the cut site. Blood clotting is performed by another type of blood cells called blood platelets.

Two types of vessels are present in the human body. They are called veins and arteries. Arteries mainly carry blood to different parts of the body. Veins carry blood from different parts of the body to the heart. As we inhale, the lung is filled with oxygen. The oxygen is taken up from the lungs by the veins and transported to the heart. The heart pumps the oxygenated blood to different parts of the body through the arteries.

Similarly, the different cells of the body use this oxygen and release carbon dioxide. The carbon dioxide is taken up by the veins and is returned to the heart. Another set of arteries carries the deoxygenated blood from the heart to the lungs. The pressure at which the heart pumps the blood is very high. For that reason, arteries have thick muscular and elastic walls.

However, the veins do not have to endure the high pressure of blood flow through them. That is why veins have thin walls. Moreover, the veins contain valves that ensure that the blood flows in one direction only, i.e., towards the heart. 

When the arteries reach the tissues, they divide into smaller, finer vessels called arterioles, which further subdivide to form extremely thin capillaries. These capillaries are the site of exchange of oxygen and carbon dioxide between the blood and the cells of the tissue. These capillaries then rejoin and form venules, which further rejoin to form veins. The veins then empty the blood into the heart. 

The heart is an essential organ of the body which pumps blood to different parts of the body in a non-stop manner. It is located in the middle of the chest cavity. However, you will feel your heartbeat to the left side of your chest. You observe this phenomenon because its lower tip is tilted towards the left. You will find that your heart and your fist are almost the same sizes.

There are four chambers of the heart. The upper two chambers are called the auricles (or the atria, singular atrium). The lower two chambers are called the ventricles. These chambers function together to prevent the mixing of the oxygenated and the deoxygenated blood with the help of the partition between the chambers. 

The walls of the four chambers of the heart are made up of muscles that relax and contract in a rhythmic manner. This process of contraction and relaxation in a rhythm forms the heartbeat. You can feel the heartbeat by placing your hand on the left side of your heart. Doctors listen to the heartbeat with the help of a stethoscope. The stethoscope amplifies the heartbeat. It has a chest piece carrying a sensitive diaphragm, a tube connecting the chest piece with two earpieces. By listening to the amplified heartbeat, doctors can identify any change in the heartbeat pattern, which can be linked to conditions of any disease. 

Other organisms can also contain blood, despite not having a proper circulatory system. For example, in hydra and sponges, water entering the body brings food and oxygen and picks up carbon dioxide and waste products as it leaves the body. Water performs the function of the blood in the body of these organisms.

11.2 Excretion in Animals

The waste products of the body are transferred to the blood. However, a mechanism for filtering the blood to remove the waste product is necessary. The filtering of blood is done by the blood capillaries present in the kidneys. 

The blood going to the kidneys contains both useful and waste materials. The useful products are filtered out back into the blood, while the wastes are dissolved in water and excreted as urine. The urine is transferred from the kidneys into the tubular ureters, which pour it into the urinary bladder. The urine is then passed out from the bladder through an opening at the mouth of a muscular tube known as the urethra. The excretory system comprises the kidneys, ureters, urinary bladder, and the urethra.

An adult human body normally produces about 1-1.8 liter of urine every day. The urine contains 2.5% of urea, 2.5% of other waste components, and 95% of water. 

Another form of excretion is sweating. Sweating consists of water and salts of the body. The round patches formed at the underarm of our clothes is due to the salt present in the sweat. Sweat functions to cool off our bodies. 

The availability of water determines how waste chemicals are excreted from the body. Aquatic animals like several fishes excrete waste products in the form of ammonia. Some animals like lizards, birds, excrete waste in the form of uric acid, which is a white-coloured semi-solid compound. Humans majorly excrete waste in the form of urea.

If a person suffers from kidney failure due to infection, injury, and other reasons, the waste products of the body accumulate in the blood. This is a life-threatening condition. Dialysis is performed for such a person, where the blood is filtered with the help of an artificial kidney.

11.3 Transport of Substances in Plants

You have learned by now that plants take water, nutrients, and minerals from the soil with the help of the roots and send it to the leaves. The leaves produce the food of the plant with sunlight and carbon dioxide through the process of photosynthesis. Every cell in a living being produces energy by the breakdown of glucose, obtained from their food. The food prepared by the leaves is transported to different parts of the plant. 

Plants absorb water and minerals with the help of root hairs present on the roots. The root hairs provide increased surface area for more absorption of water, nutrients, and minerals by being in contact with them. Plants have pipe-like vessels called xylem to transport water and nutrients from the roots to the leaves. The tube consists of specialized cells forming a vascular tube. It forms a network of different channels that ultimately transfer to the leaves. 

The food prepared in the leaves is transported to different parts of the plant by another set of vascular tissue called the phloem. Therefore, xylem and phloem take care of the transport of substances in the plant body.

10.4 What Do We Breathe Out

The water that is absorbed by the plants is not completely utilized in the food-making process. A large portion of the absorbed water is given out by the plants by a process called transpiration. Transpiration takes place through the stomata of the leaves. This evaporation of water from the leaves creates a suction pull strong enough to pull water up the xylem through great heights. Transpiration also plays a role in the cooling of plants.

Exercise 10.4 total Solutions: 15 Questions (13 short questions and 2 Long questions).

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