Class VII – Science

Chapter 2: Nutrition in Animals

VI. Case Study Based Questions

1. The small intestine is a highly coiled structure. It is about 7.5 meters long. It receives secretion from the liver and the pancreas. The liver is a reddish brown gland located in the upper part of the abdomen on the right side. The pancreas is a large cream-colored gland located just below the stomach that secretes pancreatic juice.
   1. a) The liver secretes __________.
      Answer: bile juice
   2. b) The gland associated with the alimentary canal are:
      Answer: (iv) salivary glands, liver, and pancreas
   3. c) What happens when partially digested food reaches the lower part of the small intestine?
      Answer: The partially digested food is mixed with bile juice and pancreatic juice for further digestion and absorption.
2. Amoeba is a microscopic single-celled organism found in pond water. It has a cell membrane, a rounded, dense nucleus, and many small bubbles like vacuoles in its cytoplasm. Amoeba constantly changes its shape and position. It pushes out one or more finger-like projections called pseudopodia or false feet for movement or capture of food.
   1. a) Pseudopodia are used for __________ and __________.
      Answer: movement, capturing food
   2. b) Amoeba constantly changes its shape by pushing out one or more finger-like projections called __________ and __________.
      Answer: pseudopodia, false feet
   3. c) The tips of pseudopodia fuse to form a __________.
      Answer: food vacuole
   4. d) The undigested food is thrown out of the body by __________.
      Answer: exocytosis

VII. Think and Tell

1. i) HCl is secreted by the stomach is corrosive in nature being an acid but stomach remains safe from it. Why?
   Answer: The stomach is protected by a thick layer of mucus that prevents the acid from damaging the stomach lining.
2. ii) Why does an infant, after feeding on milk, often vomit a curd-like substance?
   Answer: The milk proteins are curdled by the acidic environment in the stomach, resulting in the formation of curd-like substance.
3. iii) If a piece of chapatti is chewed for some time, it tastes sweeter. Why?
   Answer: Saliva contains the enzyme amylase which breaks down starch in the chapatti into simple sugars, making it taste sweeter.
4. iv) Why do ruminants digest their food in two steps?
   Answer: Ruminants have a specialized stomach with four chambers that allow them to digest food through microbial fermentation and then further break it down in the stomach.
5. v) Priya is eating her food hurriedly because lunch time is about to be over. Suddenly, she starts coughing. Why?
   Answer: Eating hurriedly can cause food to enter the windpipe instead of the esophagus, leading to choking and coughing as the body tries to clear the windpipe.

VIII. Higher Order Thinking Questions

1. When food is put in our mouth, the teeth cut, chew, and grind it. The glands A present in the mouth secretes watery liquid B which helps to digest component C present in the food partially. This partial digested food then passes through tube D into an organ E. The inner walls of organ E secrete mucus, hydrochloric acids, and digestive juices.
   1. a) What are (i) A, (ii) B, (iii) C, (iv) D, and (v) E?
      Answer: (i) Salivary glands, (ii) Saliva, (iii) Starch, (iv) Esophagus, (v) Stomach
   2. b) Name the component of food which is broken down by the digestive juices secreted by E.
      Answer: Proteins
2. The digested food in the small intestine is absorbed into blood vessels in the walls of the small intestine through millions of tiny finger-like outgrowths called W. The undigested food and unabsorbed food from the small intestine enters into another organ X. The organ X absorbs most of the undigested waste food material making it semisolid. This semisolid is stored in part Y of organ X for some time. It is passed out from the body through part Z in the form of faeces.
   1. a) What are W, X, Y, and Z respectively?
      Answer: W: Villi, X: Large intestine, Y: Rectum, Z: Anus
   2. b) What is the name of the process in which undigested waste is thrown out of the body?
      Answer: Egestion
   3. c) The bacteria on the dirty teeth convert the sugar in food into a substance X that causes tooth decay.
      (i) Name the substance X.
      Answer: Acid
   4. (ii) Which part of the tooth does it affect?
      Answer: Enamel

IX. Picture Based Questions

1. Identify the structures X and state its importance.
   Answer: X is tentacles. They help in capturing food and movement in organisms like hydra.
2. Identify X in the picture shown and state its importance.
   Answer: X is proboscis in the butterfly. It is used for sucking nectar from flowers.
3. Identify and define the process shown in the picture.
   Answer: The process shown is peristalsis. It is the rhythmic contraction and relaxation of muscles to move food through the digestive tract.
4. a) Name the part labelled X.
   Answer: Villi
5. b) Where are these structures present?
   Answer: In the small intestine.
6. c) What is the function of the structure labelled X?
   Answer: They increase the surface area for absorption of nutrients.
7. The main function of structure X is to:
   Answer: Absorb digested food into the bloodstream.
8. Identify the organs in the given diagram of the human digestive system that help in:
   1. A) Digestion of milk protein.
      Answer: Stomach
   2. B) Assists in digestion of proteins.
      Answer: Pancreas
   3. C) Absorption of excess water.
      Answer: Large intestine
   4. D) Structure of the human digestive system where no digestion takes place.
      Answer: Esophagus