CBSE Class 7 Science Chapter 2: Nutrition in Animals NCERT Solutions

(a) The main steps of nutrition in humans are ingestion, digestion, absorption, assimilation, and egestion. These steps describe the entire process from taking food into the body to eliminating waste.

(b) The largest gland in the human body is the liver. It produces bile, which is essential for fat digestion.

(c) The stomach releases hydrochloric acid and digestive juices which act on food. Hydrochloric acid creates an acidic medium, while digestive juices break down proteins.

(d) The inner wall of the small intestine has many finger-like outgrowths called villi. These villi greatly increase the surface area available for absorbing digested nutrients.

(e) Amoeba digests its food in the food vacuole. Food particles are engulfed and then digested within these temporary vacuoles inside the cell.

(a) (F) The digestion of starch begins in the mouth with the enzyme salivary amylase, not in the stomach.

(b) (T) The tongue plays a crucial role in mixing food with saliva during chewing, which helps in the initial breakdown of carbohydrates.

(c) (T) The gall bladder is a small organ that stores and concentrates bile produced by the liver before releasing it into the small intestine.

(d) (T) Ruminants, such as cows and sheep, have a specialized digestive system where they regurgitate partially digested food (cud) from the stomach back into the mouth for further chewing.

1. Fat is completely digested in the (iii) small intestine <math>\sqrt{\phantom{a}}</math>. Here, bile emulsifies fats, and lipase enzymes break them down into fatty acids and glycerol.
2. Water from the undigested food is absorbed mainly in the (iv) large intestine <math>\sqrt{\phantom{a}}</math>. The large intestine absorbs most of the remaining water, solidifying the waste material before egestion.

The correct matching is:

Column I (Food components) Column II (Product(s) of digestion)

Carbohydrates ---------------- Sugar

Proteins ---------------- Amino acids

Fats ---------------- Fatty acids and glycerol

Carbohydrates are broken down into simple sugars like glucose. Proteins are digested into amino acids. Fats are digested into fatty acids and glycerol.

Villi (singular: villus) are tiny, finger-like projections that line the inner walls of the small intestine. Their primary location is the inner surface of the small intestine, specifically in the jejunum and ileum.

The main function of villi is to significantly increase the surface area of the small intestine. This larger surface area allows for more efficient and rapid absorption of digested food materials, such as glucose, amino acids, fatty acids, and glycerol, into the bloodstream and lymphatic system.

Each villus contains a network of capillaries and a lacteal (a lymphatic vessel). Digested nutrients are absorbed through the walls of the villi into these blood vessels and the lacteal for transport to all parts of the body.