Exercises: Nutrition in Animals
Objective type Questions
A. Fill in the blanks with the correct words.
Q.1. _____(Assimilation/Digestion) involves the use of simple substances to build complex substances required by the body.
Ans: Assimilation
Assimilation is the process by which the small, digested molecules are used by cells to build larger, complex substances and to repair or replace body tissues. It follows digestion and absorption and helps the body grow and maintain its functions.
Q.2. Once swallowed, the food passes down into a long tube called the _____(stomach/oesophagus).
Ans: Oesophagus
The oesophagus is a muscular tube that connects the mouth to the stomach. It pushes the swallowed food into the stomach by rhythmic muscular contractions called peristalsis.
Q.3. The process of digestion begins in the_____(mouth/stomach).
Ans: Mouth
Digestion begins in the mouth where food is broken down mechanically by chewing and mixed with saliva. Saliva contains an enzyme that starts breaking down starch into simpler sugars.
Q.4. The liver secretes the,_____(bile/pancreatic) juice.
Ans: Bile
Bile is a greenish-yellow fluid produced by the liver and stored in the gallbladder. It helps in digestion by emulsifying fats into tiny droplets, which makes it easier for digestive enzymes to act on them.
Q.5. The digestion of various components of food is completed in the _____(large/small) intestine.
Ans: Small intestine
Most digestion and absorption take place in the small intestine. Enzymes from the pancreas and the small intestine break down carbohydrates, proteins and fats into molecules that can be absorbed into the blood.
Q.6. _____ (Rumen/Abomasum) is the last chamber of the stomach in ruminants.
Ans: Abomasum
In ruminants (for example, cows and sheep) the abomasum is the fourth and final stomach chamber. It works like the stomach of non-ruminant animals by mixing food with gastric juices and enzymes to digest proteins.
B. Choose the correct option.
Try yourself: In which of these processes is food broken down into simpler substances?
Try yourself: Which of these are flat blade-like teeth used for cutting food?
Try yourself: What do fats break down into?
Try yourself: In which of these chambers of ruminants does the food get partially digested and stored as the cud?
Try yourself: Which of these nutrients gets mostly digested in the small intestines?
Try yourself: With the help of which of the following does a hydra catch its food?
Try yourself: Which of these help to digest food in an amoeba?
Try yourself: Which of these primarily helps in the digestion of fats in human beings?
Try yourself: Which of these act as energy reserves and are stored for later use?
Try yourself: Which of these is not a chamber of the stomach of ruminants?
Very short answer type questions
Give two examples for the following.
Q.1. Organisms made of a single cell ____
Ans: Amoeba, Paramecium
Q.2. Outgrowths that help unicellular animals to catch food ____
Ans: Cilia, Flagella
Q.3. Digestive juices that aid in digestion ____
Ans: Enzymes, Hydrochloric acid
Q.4. Glands of the digestive system ____
Ans: Salivary gland, Pancreas
Short answer type questions
Q.1. How is ingestion different from egestion?
Ans: Ingestion is the intake of food into the body through the mouth, while egestion is the removal of undigested waste from the body through the anus. Ingestion brings food in; egestion removes the waste left after digestion and absorption.
Q.2. Name the four types of teeth and their main functions in the human jaw.
Ans:
- Incisors: Sharp front teeth used for biting and cutting food.
- Canines: Pointed teeth used for tearing food.
- Premolars: Broad teeth used for crushing and grinding food.
- Molars: Large, flat teeth at the back used for thorough grinding and mashing of food before swallowing.
Q.3. How do villi help in small intestines of human beings?
Ans: Villi are tiny, finger-like projections that line the inner surface of the small intestine. They increase the surface area for absorption and contain blood vessels and lacteals that transport absorbed nutrients into the bloodstream and lymphatic system.
Q.4. What is rumination?
Ans: Rumination is the process in ruminant animals where partly digested food is regurgitated from the stomach to the mouth, chewed again (cud), and then swallowed. This helps to break down tough plant material further so microbes can act on it efficiently.
Long answer type questions
Q.1. With the help of a well-labelled diagram, describe how an amoeba catches and digests its food.
Ans: An amoeba captures and digests food by forming extensions of its cell membrane called pseudopodia and then digesting the food inside a food vacuole.
Key steps:
- The amoeba moves its pseudopodia around the prey or food particle and engulfs it, forming a pocket.
- The pocket closes to form a food vacuole inside the cytoplasm.
- Lysosomes fuse with the food vacuole and release digestive enzymes into it.
- Enzymes break down the food into small soluble molecules, which are absorbed into the cytoplasm.
- Undigested material is expelled from the cell by the vacuole moving to the cell surface and releasing its contents (exocytosis).
Q.2. Explain the process of digestion in human beings.
Ans: Digestion in humans is a step-by-step process in which food is broken down into small molecules that the body can absorb and use.
Mouth: Food is chewed by the teeth and mixed with saliva. Saliva contains an enzyme that begins to break down starch into simpler sugars.
Oesophagus: The chewed food (bolus) is pushed down to the stomach by rhythmic muscle movements called peristalsis.
Stomach: Food is mixed with gastric juices containing hydrochloric acid and enzymes. Proteins begin to be broken down into smaller peptides.
Small intestine: Partly digested food enters the small intestine where bile (from the liver) emulsifies fats and pancreatic juices provide enzymes to further digest carbohydrates, proteins and fats. The intestinal lining also releases enzymes to complete digestion.
Absorption: The digested molecules (glucose, amino acids, fatty acids and glycerol) are absorbed through the walls of the small intestine into blood vessels and lacteals and carried to the liver and other body parts.
Large intestine: Water and some minerals are absorbed; the remaining undigested material becomes faeces.
Rectum and Anus: Faeces are stored in the rectum and removed through the anus.
Q.3. How do nutrients get assimilated after digestion in the human body?
Ans: After digestion, nutrients are absorbed and then assimilated (used or stored) by the body as follows:
Carbohydrates: Broken down into glucose, absorbed into the blood and taken to the liver. Excess glucose is stored as glycogen in the liver and muscles for later energy use.
Proteins: Broken down into amino acids, absorbed into the blood and carried to the liver and tissues where they are used to make new proteins or, if in excess, converted to other compounds.Fats: Broken down into fatty acids and glycerol, absorbed into the lymphatic system as tiny droplets and then into the blood. Fats are used for energy, to build cell membranes and to store energy in fat tissue.
Q.4. Describe in brief the process of digestion in ruminants.
Ans: Ruminants (for example cows, sheep and goats) have a four-chambered stomach that helps them digest plant material rich in cellulose. The four chambers are the rumen, reticulum, omasum and abomasum.
Main points:
After these steps the digested nutrients are absorbed in the small intestine and the undigested waste passes into the large intestine and is excreted.
- Rumen: Food is stored here and partially broken down by microbes; fermentation helps to break cellulose into simpler substances.
- Reticulum: Small particles and heavy items are separated here. Food is often regurgitated from the reticulum as cud for further chewing (rumination).
- Omasum: Water and many mineral salts are absorbed here.
- Abomasum: The last chamber acts like the stomach of non-ruminants; it secretes gastric juices and enzymes to digest proteins.
