GSEB Class 7 Science Solutions Chapter 2 Nutrition in Animals

 

Question 1. Fill in the blanks:
(a) The main steps of nutrition in humans are ingestion, digestion, absorption, assimilation, and egestion.
(b) The largest gland in the human body is liver.
(c) The stomach releases hydrochloric acid and digestive juices which act on food.
(d) The inner wall of the small intestine has many finger-like outgrowths called villi.
(e) Amoeba digests its food in the food vacuole.
Answer:
(a) ingestion, digestion, absorption, assimilation, egestion
(b) liver
(c) digestive
(d) villi
(e) food vacuole.
In simple words: Humans eat, digest, absorb, use nutrients, and then remove waste. The liver is the biggest gland. The stomach uses acid and digestive juices for food. Tiny fingers in the small intestine are called villi. Amoeba stores and digests food in a food vacuole.

Exam Tip: Remember the five main steps of nutrition in the correct order, and recall the primary function of each organ mentioned in the blanks.

 

Question 2. Mark 'T' if the statement is true and 'F' if it is false:
(a) Digestion of starch starts in the stomach.
(b) The tongue helps in mixing food with saliva.
(c) The gall bladder temporarily stores bile.
(d) The ruminants bring back swallowed grass into their mouth and chew it for some time.
Answer:
(a) False
(b) True
(c) True
(d) True
In simple words: Starch digestion begins in the mouth, not the stomach. The tongue mixes food with spit. The gall bladder holds bile for a while. Ruminants chew their food again after swallowing it the first time.

Exam Tip: Understand where each stage of digestion primarily occurs to correctly identify true or false statements about the digestive process.

 

Question 3. Tick mark the correct answer in each of the following:
(a) Fat is completely digested in the
(i) stomach
(ii) mouth
(iii) small intestine
(iv) large intestine
Answer: (iii) small intestine
In simple words: Fats are fully broken down and processed in the small intestine.

Exam Tip: Recall the specific roles of each organ in the digestive system to correctly identify where complete digestion of different food types takes place.

(b) Water from the undigested food is absorbed mainly in the
(i) stomach
(ii) foodpipe
(iii) small intestine
(iv) large intestine
Answer: (iv) large intestine
In simple words: The large intestine is where most of the water is taken out of food waste before it leaves the body.

Exam Tip: Focus on the primary function of the large intestine, which is the absorption of water and certain electrolytes from indigestible food matter.

 

Question 4. Match the items of Column I with those given in Column II:

Exam Tip: Understand that complex food components are broken down into simpler, absorbable forms. Carbohydrates break down into sugars, proteins into amino acids, and fats into fatty acids and glycerol.

 

Question 5. What are villi? What is their location and function?
Answer: Villi are tiny, finger-like projections found on the inner walls of the small intestine. These structures are located exclusively within the small intestine. Their main job is to significantly increase the surface area available for the absorption of digested food particles. This expanded area allows for a more efficient transfer of nutrients into the bloodstream.
In simple words: Villi are small, finger-shaped parts inside the small intestine. They help to make the surface bigger so more food can be soaked up into the body.

Exam Tip: When describing villi, ensure you mention their finger-like shape, their location in the small intestine, and their crucial role in increasing surface area for absorption.

 

Question 6. Where is the bile produced? Which component of the food does it help to digest?
Answer: Bile is made in the liver. This bile liquid is then kept in a small sac known as the gall bladder. Its primary role is to assist in the breakdown and processing of fats during digestion, making them easier to absorb.
In simple words: Bile is made in the liver and stored in the gall bladder. It helps to digest fats in our food.

Exam Tip: Clearly distinguish between where bile is produced (liver) and where it is stored (gall bladder), and remember its specific function in fat digestion.

 

Question 7. Name the type of carbohydrate that can be digested by ruminants but not by humans. Give the reason also.
Answer: Cellulose is the specific kind of carbohydrate that ruminants can digest, but humans cannot. Ruminants possess a large, pouch-like structure positioned between their small intestine and large intestine. The cellulose present in their food is broken down by the activity of particular bacteria that are not found in the human digestive system. These specialized bacteria allow ruminants to extract nutrients from cellulose.
In simple words: Ruminants can digest cellulose, which is a type of carbohydrate, but humans cannot. This is because ruminants have special bacteria in their gut that break down cellulose, and humans do not have these bacteria.

Exam Tip: The key difference lies in the presence of specialized bacteria in ruminants that produce cellulase, an enzyme necessary to break down cellulose; humans lack this enzyme and the associated gut structure.

 

Question 8. Why do we get instant energy from glucose?
Answer: We get fast energy from glucose because it breaks down very easily inside cells with the assistance of oxygen. This quick breakdown immediately supplies energy to the body. Glucose does not require prior digestion; it is directly absorbed into the bloodstream from the digestive tract.
In simple words: Glucose gives us quick energy because it breaks down easily in our cells with oxygen. It goes straight into our blood without needing digestion first.

Exam Tip: Emphasize that glucose is a simple sugar, meaning it doesn't need to be broken down further, and its direct absorption and rapid cellular respiration lead to instant energy.

 

Question 9. Which part of the digestive canal is involved in:
(i) absorption of food
(ii) chewing of food
(iii) killing of bacteria
(iv) complete digestion of food
(v) formation of faeces
Answer:
(i) Small intestine
(ii) Mouth
(iii) Stomach
(iv) Small intestine
(v) Large intestine
In simple words: Food is taken in by the mouth, digested in the stomach and small intestine, nutrients are absorbed in the small intestine, and waste forms in the large intestine.

Exam Tip: Know the specific primary roles of each major organ in the digestive system, as they are often tested in this format.

 

Question 10. Write one similarity and one difference between the nutrition in amoeba and human beings.
Answer:
Similarity: Both amoeba and human beings utilize digestive juices to break down complex food into simpler, soluble, and absorbable substances. In amoeba, these juices are released into the food vacuole, while in humans, they are secreted in the stomach and small intestine.
Difference: Amoeba captures its food by extending temporary finger-like projections called pseudopodia and then engulfs it entirely. In contrast, human beings take in food through their mouth, and the digestion process involves a more complex, specialized digestive system.
In simple words: Both amoeba and humans use special liquids to break down food. But amoeba catches its food by wrapping around it, while humans eat food through their mouth.

Exam Tip: When comparing organisms, clearly state both a point of resemblance and a point of distinction, focusing on the core mechanisms of nutrition.

 

Question 11. Match the items of Column I with suitable items in Column II.

Exam Tip: Understand the specific functions of each organ in the digestive system to correctly match them with their respective roles or secretions.

 

Question 12. Label Fig. of the digestive system, (as given in the NCERT Textbook Exercise)
Answer:

In simple words: The diagram displays the main parts of the human digestive system, showing the stomach, intestines, and other connected organs.

Exam Tip: Be able to identify and accurately label all the major organs of the human digestive system in a diagram, understanding their correct positions.

 

Question 13. Can we survive only on raw, leafy vegetables/grass? Discuss.
Answer: Animals, fungi, bacteria, non-green plants, and human beings lack the ability to produce their own food. They rely on autotrophs, like green plants, either directly or indirectly for their sustenance. Green plants, such as leafy vegetables and grass, capture solar energy to create their own food in the form of glucose. While leafy vegetables and grass can supply enough energy for survival, humans cannot live solely on raw, uncooked vegetables. This is because these vegetables contain cellulose, a complex carbohydrate that the human digestive system is unable to break down.
In simple words: Humans cannot live only on raw, leafy vegetables or grass because our bodies cannot digest cellulose, which is found in these foods. We need other nutrients that our digestive system can process.

Exam Tip: Understand the concept of autotrophs and heterotrophs, and recall that humans, as heterotrophs, cannot digest cellulose due to the absence of the necessary enzymes.

 

Extended Learning - Activities and Project

 

Question 1. Visit a doctor and find out:
(i) Under what conditions does a patient need to be on a drip of glucose?
(ii) Till when does a patient need to be given glucose?
(iii) How does glucose help the patient recover?
Write the answers in your notebook.
Answer:
(i) A patient might need a glucose drip if they are unable to consume food or digest it properly, or if there is an urgent need to provide immediate energy to the body, for example, during severe illness or surgery.
(ii) Glucose is typically given to a patient until their condition stabilizes, they are no longer in critical danger, or they can resume eating and digesting food on their own.
(iii) Glucose assists a patient's recovery because it does not need to be digested. It is directly absorbed into the bloodstream, and its breakdown in the cells quickly provides energy. This rapid energy supply helps the patient to regain strength and recover faster.
In simple words: Patients get glucose drips when they can't eat or need quick energy. They get it until they are out of danger. Glucose helps them recover fast by giving instant energy directly to the body.

Exam Tip: Understand that glucose provides immediate energy because it's a simple sugar that doesn't require digestion and is absorbed directly into the blood.

 

Question 2. Find out what vitamins are and get the following information.
(i) Why are vitamins necessary in the diet?
(ii) Which fruits or vegetables should be eaten regularly to get vitamins? Write a one-page note on the information collected by you. You may take help of a doctor, a dietician, your teacher or any other person, or from any other source.
Answer:
Vitamins: These are a group of natural compounds found in many foods that are vital for good health. They are needed in small amounts for various body functions.
(i) Vitamins are essential in our diet because they help protect our bodies from illnesses and diseases. They also play a crucial role in maintaining the health of our eyes, bones, teeth, and gums, ensuring overall well-being.
(ii) To obtain sufficient vitamins, we should regularly eat a variety of fruits and vegetables. Examples include carrots, spinach, other leafy vegetables, citrus fruits like oranges, tomatoes, papaya, bananas, cauliflower, gourds, beans, germinating grams, and pineapple. It is especially important to eat fruits and vegetables that are in season. Students are encouraged to research and compile their own notes on this topic.
In simple words: Vitamins are important tiny helpers in food that keep us healthy and prevent sickness. Eating many different fruits and vegetables, especially those in season, helps us get all the vitamins we need.

Exam Tip: Remember that vitamins are micronutrients vital for specific bodily functions and disease prevention, and a balanced diet rich in seasonal fruits and vegetables is the best source.

 

Question 3. Collect data from your friends, neighbours and classmates to know more about "milk teeth". Tabulate your data. One way of doing it is given below:

Answer: To complete this activity, you should interview at least twenty children, along with their parents or guardians. Ask them about the age when their first milk tooth fell out and the age when their last one was lost. Record how many milk teeth they lost in total and how many permanent teeth have grown in to replace them. After collecting all this information, you can calculate the average age at which children in your group tend to lose their milk teeth. This task requires active data collection and observation.
In simple words: Talk to friends and family to learn when children lose their baby teeth. Write down the ages and counts in a table, then find the average age for losing milk teeth.

Exam Tip: For data collection activities, ensure your methodology is clear, you collect enough samples, and you accurately record and analyze the information to draw a valid conclusion.