Kerala Syllabus Class 7 Basic Science: Chapter 05 Human Body: A Wonder Digestion and Respiration - Questions and Answers


Questions and Answers for Class 7 Basic Science (English Medium) മനുഷ്യശരീരം ഒരു വിസ്‌മയം: ദഹനവും, ശ്വസനവും | Text Books Solution Basic Science (English Medium) Chapter 05 Human Body: A Wonder  Digestion and Respiration - Teaching Manual | Teachers Handbook

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ഈ ബ്ലോഗ് അഡ്‌മിൻറ രേഖാമൂലമുള്ള അനുമതിയില്ലാതെ ഈ ബ്ലോഗിൽ നൽകിയിരിക്കുന്ന ചോദ്യോത്തരങ്ങൾ, ഇതേരീതിയിലോ പി.ഡി.എഫ് രൂപത്തിലോ, മറ്റേതെങ്കിലും ഡിജിറ്റലോ, പ്രിന്റഡ് ഉൾപ്പെടെയുള്ള ഏതെങ്കിലും രൂപങ്ങളിലേക്കോ മാറ്റി മറ്റൊരു വെബ്സൈറ്റിലോ, ബ്ലോഗിലോ, യുട്യൂബ്, സോഷ്യൽ മീഡിയാ ഗ്രൂപ്പുകളിലോ ഉൾപ്പെടെ ഒരിടത്തും പ്രചരിപ്പിക്കാൻ പാടില്ലാത്തതാകുന്നു.

Std 7: Basic Science Chapter 05: Human Body: A Wonder Digestion and Respiration - Questions and Answers
♦ Compile a list of the organisms you have observed and their respective food.
Name of the organism Food
• Cow• Grass
• Straw
• Goat• Leaves
• Banana peel
• Cat• Mice 
• Fish 
• Bear• Honey 
• Fish
• Rabbit• Carrot
• Leaves 
• Human• Cooked rice
• Fish
♦ Classify the living organisms into herbivore, carnivore and omnivore. 
 Herbivores
(eat plants)		 Carnivores
(eat meat):		 Omnivores
(eat both plants and meat)
 • Cow
 • Elephant
 • Rabbit
 • Deer 
 • Giraffe		 • Lion
 • Tiger
 • Tiger
 • Shark
 • Wolf		 • Human
 • Bear
 • Pig
 • Crow
 • Dog

♦ What is Nutrition?
Nutrition is the process by which organisms obtain and utilize food.

♦ What is Ingestion?
• There are 5 stages in nutrition. 
• The first stage is ingestion. 
• The food first reaches the mouth. 

♦ What are the changes that occur to food in the mouth?
● It mixes with saliva.
● Food is chewed with the help of teeth
● Digestion begins in the mouth

♦ What is the role of lips, tongue and teeth in ingestion?
• Lips - To prevent food from spilling out
• Tooth - to chew 
• Tongue - to move food between the teeth, to taste

♦ ------------ is the outermost layer of the tooth. 
Enamel 

♦ The hardest substance in the human body.
Enamel 

♦ Teeth
• Teeth are used to masticate food. 
• The structure and arrangement of teeth is suitable for biting, chewing and grinding food.
• Enamel is the outermost layer of the tooth. 
• It is also the hardest substance in the human body.

♦ What is Milk Teeth?
• In infants, teeth development starts around the age of six months. These teeth are known as milk teeth. 
• Ten milk teeth each develop at the upper and lower jaws (in total 20).

♦ What is Permanent Teeth?
• Permanent teeth are those that replace milk teeth when they fall off. 
• If permanent teeth break or fall off, new teeth will not grow in its place.
♦ Tabulate the position and use of different types of teeth.
 Different types
of teeth 		 Position and number Uses
 • Incisor • Eight incisors in front;
four in the upper jaw and
four in the lower jaw.		 • To bite and tear
food items. 
 • Canine • Four canines adjacent to
incisors on both sides; two
in the upper and two in the
lower jaws.		 • To tear and
cut food.
 • Premolar • Eight premolars adjacent to
canines; two on both sides, in
the upper and lower jaws.		 • To chew and
grind food.
 • Molar • Twelve molar teeth near the
premolars on both sides at the back.
Six in the upper jaw and six
in the lower jaw.		 • To chew and
grind food.

♦ The generic name for molars and premolars is --------------.
molars

♦ How closely is the shape of the teeth related to their food habits in carnivorous and herbivorous animals?
• The canines of carnivores are much developed and it helps in biting and tearing meat. 
• Incisors in herbivores help to bite and tear the food and premolars and molars, to masticate the food.

♦ Tooth Decay
Tooth enamel is a calcium compound. It reacts with acid and gets damaged gradually, causing tooth decay.

♦ What is the reason for dental caries?
If we don’t clean the mouth properly after having food, bacteria will feed on the food particles struck between the teeth. This will result in lactic acid production and damage the teeth. 

♦ Lactic acid is a very weak acid. How does it cause tooth decay? 
Enamel is a calcium compound, it reacts with lactic acid and causes tooth decay.

♦ What are the functions of the tongue?
• Helps in swallowing.
• Tongue helps to move food inside the mouth so that teeth can chew it.
• The taste buds on the tongue help us to sense taste.

♦ Saliva also plays an important role in the digestive process. Saliva is produced from ----------------.
Salivary glands

♦ To which part of the digestive system does food first reach from the mouth?
Oesophagus
♦ What is oesophagus?
• The oesophagus is a long tube that connects the mouth to the stomach. 
• It is made of muscles.
• The chewed food reaches the stomach through the oesophagus.

♦ What is peristalsis?
The wave-like movement of the oesophageal wall helps food to reach the stomach. This movement is called peristalsis.

♦ What is Digestion?
• Digestion is the process in which the organic factors present in the food are broken down to simple components that can be absorbed by the body. 
• Digestion is the second stage of nutrition.

♦ What are the changes that occur to food in the stomach?
• Digestion is the second stage of nutrition. 
• It takes place partially in the stomach where food remains for 4 to 5 hours. 
• Due to the peristaltic movement of the stomach wall, the food is turned into a paste form. 
• Gastric juice, produced by glands in the stomach wall facilitates digestion. • Stomach wall also produces small amount of hydrochloric acid which helps in protein digestion and pathogen destruction.

♦ What are the digestive processes occur in the small intestine?
• Human small intestine is five to six meters long. 
• The absorption of nutrients takes place in the small intestine.
• Bile produced by the liver and the pancreatic juice produced by the pancreas is mixed with partially digested food in the first part of the small intestine and completes the digestion of food.

♦ How do the nutrients in the digested food get absorbed into the blood?
• Villi are the small finger-like projections present in the wall of small intestine.
• Nutrients in the digested food are absorbed into the blood through the villi.

♦ What is absorption?
• The process of the digested food being received into the body is absorption. 
• This is the third stage in nutrition

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♦ What is assimilation?
• The nutrients that reached the blood become part of the body. 
• This is the fourth stage of nutrition and this process is called assimilation.

♦ The digested food will also have substances not needed by the body. How they are eliminated?
• After the absorption of nutrients, the residues in the digested food move to the large intestine.
• Water and some salts are absorbed into the large intestine from the digestive waste as needed by body. 
• Later the digestive waste stored in the rectum is egested through the anus. 

♦ What is egestion?
• The process of digestive waste removal from our body is called egestion. 
• This is the fifth stage of nutrition.

♦ Complete the flow chart showing the various stages of nutrition.
• Ingestion ⟶ Digestion ⟶ absorption ⟶ Assimilation ⟶ Egestion
♦ Observe the diagrammatic representation of human digestive system. Write the names and functions of the labelled parts.
● A - Mouth
• The food first reaches the mouth. 
• It mixes with saliva.
• Food is chewed with the help of teeth
• Digestion begins in the mouth

● B -  Oesophagus
• The oesophagus is a long tube that connects the mouth to the stomach. 
• It is made of muscles.
• The chewed food reaches the stomach through the oesophagus.

● C - Stomach
• Due to the peristaltic movement of the stomach wall, the food is turned into a paste form. 
• Gastric juice, produced by glands in the stomach wall facilitates digestion. • Stomach wall also produces small amount of hydrochloric acid which helps in protein digestion and pathogen destruction.

● D - Small intestine
• The absorption of nutrients takes place in the small intestine.
• Bile produced by the liver and the pancreatic juice produced by the pancreas is mixed with partially digested food and completes the digestion of food.
• Villi are small finger-like projections in the wall of the small intestine. They absorb nutrients in digested food into the blood.

● E - Large intestine
• After the absorption of nutrients, the residues in the digested food move to the large intestine. 
• Water and some salts are absorbed into the large intestine from the digestive waste as needed by body.

● F - Rectum
The digestive waste stored in the rectum is egested through the anus. 

♦ Illustrate the process of nutrition in the single-celled amoeba and write the various stages of nutrition in amoeba.

• Ingestion: The amoeba engulfs a food particle using its pseudopodia. Pseudopodia, or "false feet," are temporary, arm-like projections of amoeba, to grow around and to engulf food particles.

• Digestion: The digestive enzymes break down the food particle and digest it.

• Absorption: The digested nutrients pass into the amoeba's cytoplasm.

• Assimilation: The amoeba uses these absorbed nutrients for energy, growth, and repair.

• Egestion: The amoeba expels undigested waste material from the cell.

♦ Why are humans unable to take oxygen from water, like fish?
Fishes have gills by which they absorb dissolved oxygen from water. Humans can't take oxygen from water because we don't have gills. Our lungs are designed to take oxygen from the air.

♦ What is Inhalation and Exhalation?
• Inhalation is the process of taking air into the lungs. 
• Exhalation is the process of movement of air from lungs to outside.

♦ Construct a model to understand the working of lungs.
Materials required
Y tube, one big balloon, 2 small balloons, a plastic bottle with its bottom part cut off, string, rubber band, paper ball.

Method of construction
Fix the two small balloons in the Y tube and insert it through the lid of the bottle as shown in the figure. Place a small paper ball tied to a rubber band, in the middle of the big balloon and tie it with a long string. Attach the other end of the rubber band to the Y tube. Invert the big balloon and attach at the bottom of the bottle with the free end of the string outside.

Procedure
Gently pull down the string tied to the big balloon.
(While pulling the string it will be better to hold the Y tube so as to keep it steady.)

• When the string attached to the large balloon is pulling down, the two small balloons inside the bottle begin to expand. Why?
When the string attached to the large balloon is pulled down the volume inside the bottle increases and pressure decreases. Then the air outside the bottle enters the small balloons through the Y tube. So the small balloons expand.

• Why do the small balloons shrink when the string attached to the large balloon is released?
When the string attached to the large balloon is released the large balloon moves into the bottle. Then the volume inside the bottle decreases and pressure increases. As a result, the air inside the small balloons goes out and shrinks. 

♦ Write the functioning of human lungs.
• Human lungs are placed in a space inside the chest called the thoracic cavity.
• Below the thoracic cavity is the abdomen. 
• Diaphragm is the muscular wall that separates the thoracic and abdominal cavities. 
• There are two lungs in the thoracic cavity.
• The diaphragm and the muscles attached to the ribs play a role in the contraction and expansion of human lungs.
• During inhalation, the diaphragm contracts and flattens. This increases the volume of the thoracic cavity. The atmospheric air enters the lungs and the lungs expand.
• During exhalation, the diaphragm relaxes and both the diaphragm and the lungs return to their previous positions. The air from the lungs moves out. 
♦ What happens to the diaphragm during inhalation and exhalation?
• During inhalation, the diaphragm contracts and flattens. This increases the volume of the thoracic cavity. The atmospheric air enters the lungs and the lungs expand.
• During exhalation, the diaphragm relaxes and both the diaphragm and the lungs return to their previous positions. The air from the lungs moves out. 

♦ When does the thoracic cavity increase in volume- during inhalation or exhalation?
Inhalation

♦ What is Respiratory Tract?
Air entering through the nostrils reaches alveoli of the lungs. Respiratory tract is this air passage from nostrils to lungs.

♦ Complete the flowchart of the respiratory tract using the indicators.
Indicators: Alveolus, Trachea, Bronchioles, Nostrils, Bronchi.
Answer:
Nostrils 
    ⇩
Trachea 
    ⇩
Bronchi
    ⇩
Bronchioles
    ⇩
Alveolus 

♦ Write the different stages of inhalation and exhalation.
● Inhalation 
• The diaphragm contracts and flattens slightly. Rib cage lift upwards.

• The volume of the thoracic cavity increases. The lungs expand.

• Atmospheric air enters the lungs. 

● Exhalation 
• The diaphragm returns to the previous state and the rib cage moves down.

• The volume of the thoracic cavity decreases and lungs contract.

• The air from the lungs moves out. 

♦ Observe the table showing the levels of various components in the inhaled and exhaled air. 
● Is the level of all components in inhaled and exhaled air the same? 
No

● Which all components show difference in percentage?
Oxygen
Carbon dioxide
Moisture

● Which of the components are in higher level and lower level in exhaled air than in inhaled air? 
Higher level - Carbon dioxide, Moisture
lower level - Oxygen

● Which gas is utilized by us in respiration?
Oxygen

♦ What first aid should be given when food gets stuck in the trachea? 
• If the food is stuck in the trachea, that person should be asked to cough forcefully. With the force of cough, the food will be ejected.   
• Keep the person who has difficulty in breathing in a slightly bent position. With both hands, press firmly on the affected person's stomach from behind. If necessary, repeat this process for a few more times. 
• If the affected person is a baby,  place the baby face down on your forearm. Your arm should be resting on your thigh. With the palm of your other hand, give the child forceful blows between the shoulder blades. Provide medical attention if necessary.

♦ How gas exchange take place in paramecium?
• Paramecium is an aquatic unicellular organism that cannot be seen with the naked eye. 
• Paramecium takes in oxygen dissolved in the surrounding water through the cell membrane and gives out carbon dioxide.

● Which part helps in the respiration of earthworms?
Moist skin

● Which part helps in the respiration of Fish?
Gills

● Which part helps in the respiration of frogs?
Lungs (while on land)
Moist skin (underwater)

● Which part helps in the respiration of Spider?
Book lungs

♦ What is respiration?
The process through which organisms receive oxygen from their environment and eliminate carbon dioxide is called respiration.

♦ Respiration in plants
Plants also absorb oxygen from the atmosphere and release carbon dioxide. Stomata are fine pores, found in leaves and tender stem that help in gas exchange in plants.

● Which gas do plants take in during respiration?
Oxygen

● Name the gas released by plants during respiration?
Carbon dioxide

● Where does the gas exchange take place in plants?
Stomata.
Stomata are fine pores, found in leaves and tender stems.
Let’s Assess

1. Which of the following combinations is correct?
a.  Goat, Horse, Crow, Pigeon (Herbivores)
b.  Leopard, Vulture, Elephant, Lizard (Carnivores)
c.  Man, Hen, Monkey, Peacock (Omnivores)
Answer: c.  Man, Hen, Monkey, Peacock (Omnivores)

2.  In which of the following organ digestion is completed?
a. Mouth 
b. Small intestine 
c. Large intestine 
d. Stomach
Answer: b. Small intestine 

3. What are the precautionary steps to be taken to prevent tooth decay?
• Brush your teeth in the morning before breakfast and at night, after dinner. 
• Always clean your mouth whenever you eat something.

4. Compare the dentition of a six-year-old child and that of an adult.
• A six-year-old child has 20 teeth
• An adult has 32 teeth

5.  A person is lying down and eating food. Do you think the food will reach the stomach? Why?
Yes, The food will reach the stomach due to the peristalsis movement of the oesophagus.




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