7th Standard, Science Chapter 2
Nutrition in Animals
Exercises
- 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. - Mark if the statement is true or if it is false:
(a) Digestion of starch starts in the stomach. (T/F)
Answer: False
(b) The tongue helps in mixing food with saliva. (T/F)
Answer: True
(c) The gall bladder temporarily stores bile. (T/F)
Answer: True
(d) The ruminants bring back swallowed grass into their mouth and chew it for some time. (T/F)
Answer: True - 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
(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 - Match the items of Column I with those given in Column II:
Column I Column II
Food components Product(s) of digestion
Carbohydrates Fatty acids and glycerol
Proteins Sugar
Fats Amino acids
Answer:
Column I Column II
Food components Product(s) of digestion
Carbohydrates Sugar
Proteins Amino acids
Fats Fatty acids and glycerol
- What are villi? What is their location and function?
Answer: The inner walls of the small intestine have thousands of finger-like outgrowths. These are called villi (singular villus). The villi increase the surface area for absorption of the digested food. Each villus has a network of thin and small blood vessels close to its surface. The surface of the villi absorbs the digested food materials. - Where is the bile produced? Which component of the food does it help to digest?
Answer: The largest gland liver produce bile juice that is stored in a sac called the gall bladder. The bile plays an important role in the digestion of fats. - Name the type of carbohydrate that can be digested by ruminants but not by humans. Give the reason also.
Answer: Cellulose is type of carbohydrate that can be digested by ruminants but not by humans because ruminants have a large sac-like structure called Caecum between the oesophagus and the small intestine. The cellulose of the food is digested here by the action of certain bacteria which are not present in humans. - Why do we get instant energy from glucose?
Answer: Glucose is a most basic form of sugar. We get instant energy from glucose because. It carbohydrates when eat up easily digested and absorbed in blood. Because glucose is absorbed quickly and readily converted, it provides an immediate source of energy for cellular functions. If glucose is directly taken it does not have to be digested. That is why we get instant energy from glucose. - Which part of the digestive canal is involved in?
(i) absorption of food small intestine.
(ii) chewing of food Buccal cavity.
(iii) killing of bacteria Stomach.
(iv) complete digestion of food small intestine.
(v) formation of faeces large intestine. - Write one similarity and one difference between the nutrition in amoeba and human beings.
Answer:
Similarities:
( i) Both Amoeba and human require energy for growth and maintains of their body.
(ii) This energy is delivered from food that they eat.
(iii) After swallow food broken down into simple form by the help of digestion.
Differences:
(i) In Amoeba digestive juice secreted by food vacuole. In Human digestive juice secreted in Buccal cavity, Stomach and small intestine.
( ii) In Amoeba mouth and complex digestive system absent. In Human mouth and complex digestive system present. - Match the items of Column I with suitable items in Column II
Column I Column II
(a) Salivary gland (i) Bile juice secretion
(b) Stomach (ii) Storage of undigested food
(c) Liver (iii) Saliva secretion
(d) Rectum (iv) Acid release
(e) Small intestine (v) Digestion is completed
(f ) Large intestine (vi) Absorption of water
(vii) Release of faeces
Answer:
Salivary gland Saliva secretion
Stomach Acid release
Liver Bile juice secretion
Rectum storage of indigestion food
Small intestine Digestion is completed
Large intestine Absorption of water - Label Fig. 2.11 of the digestive system.
Additional questions and answers.
- What is rumination?
Answer: Grass eating animals quickly swallow the grass and store it in a part of the stomach called rumen. Here the food gets partially digested and is called cud. But later the cud returns to the mouth in small lumps and the animal chews it. This process is called rumination and these animals are called ruminants. - Can we survive only on raw leafy vegetable and grass? Discuss.
Answer: No. Humans cannot survive only on raw, leafy vegetable and grass because, green is rich in cellulose which is type of carbohydrate. Humans are not able to digest cellulose due to absence of cellulose digesting bacteria. Leafy vegetables and grass are rich in cellulose, a type of carbohydrate that humans cannot digest. Humans lack the specific enzymes and bacteria needed to break down cellulose into usable energy. A diet solely of raw leafy vegetables and grass would lead to deficiencies in other essential nutrients like proteins, fats, and certain vitamins and minerals. - Label the region of different tastes in a tongue.
Answer: - What is Absorption?
Answer: The major digested of all component of food takes place in small Intestine. The digested food pass into blood vessels in intestine. This process is called Absorption. - What is egestion?
Answer: Undigested and unabsorbed food particles are discharged out of the body through anus is called egestion. - What is assimilation?
Answer: In small intestine digested food pass into blood vessel. Wall of intestine has like finger is called villi. The surface of villi absorbs the digested food. Absorbed food are transferred through blood vessels to different organs of the body. This process is called assimilation. - Draw a diagram of amoeba and label its parts.
Answer: - What is caecum?
Answer: Grass eating animals have sac-like structure between food pipe and small intestine. Cellulose rich in grass easily digested by action of certain bacteria present in caecum.
Extended Learning – Activities and Project - Visit a doctor and find out:
(i) Under what conditions does a patient need to be on a drip of glucose?
Answer: A patient may need a glucose drip, or intravenous glucose infusion, when they are experiencing dehydration or low blood sugar (hypoglycaemia). Glucose is a simple sugar that can be easily absorbed by the body and provides a readily available source of energy. It is particularly useful when a patient cannot take food or fluids orally. Glucose drips can also be used in the treatment of certain conditions like diabetic ketoacidosis and as part of parenteral nutrition (feeding a patient intravenously).
(ii) Till when does a patient need to be given glucose?
Answer: A patient needs glucose (usually via an intravenous drip) until their blood glucose levels return to a safe and stable range, they are able to eat and drink normally, and their overall condition improves. This is often necessary when a patient is experiencing low blood sugar (hypoglycemia), dehydration, or is unable to consume food or fluids orally.
(iii) How does glucose help the patient recover?
Answer: Glucose helps patients recover by providing a readily available source of energy. It’s quickly absorbed into the bloodstream and can be used by cells throughout the body, especially the brain, which is highly energy-dependent. This is particularly helpful for patients who are unable to eat or digest food properly, as glucose can be administered intravenously.
Write the answers in your notebook. - 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 are crucial for maintaining overall health and well-being, as they support various bodily functions, including metabolism, immune function, and energy production. They act as catalysts for chemical reactions within the body, enabling the proper functioning of cells, tissues, and organs. Vitamins, particularly the B-complex vitamins, play a vital role in converting food into energy, ensuring that the body can effectively utilize carbohydrates, proteins, and fats. Vitamins like C and D are essential for a strong immune system, helping the body fight off infections and diseases. Vitamins D and K are crucial for maintaining healthy bones, supporting calcium absorption and preventing fractures.
To get a good intake of vitamins, regularly consume a variety of fruits and vegetables, including leafy greens, citrus fruits, and colorful options. Examples include spinach, kale, oranges, strawberries, carrots, sweet potatoes, and broccoli. Citrus fruits like oranges, grapefruits, and lemons, as well as strawberries, papaya, and bell peppers are rich in Vitamin C. - 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:
Age at which first tooth fell = 6 – 7 years
Age at which last tooth fell = 12 -13 years
Number of teeth lost = 20 Baby teeth
Number of teeth replaced = 32
