A. Choose the correct option. 1.
Ans: (b)
Explanation: Canines are pointed teeth situated next to the incisors. Their sharp, pointed edges help in holding and tearing food, especially meat and other tough items. They also assist in grasping food before it is passed to the molars for grinding.
2.
Ans: (d)
Explanation: Amoeba uses pseudopodia (finger-like extensions of its body) for movement and to engulf food. The captured food is enclosed in a food vacuole, where digestive juices break it down. Pseudopodia thus serve both to move the organism and to trap food particles, while the food vacuole carries out digestion.
3.
Ans: (a)
Explanation: Saliva contains the enzyme amylase, which begins the digestion of carbohydrates (starch) into simpler sugars while food is being chewed in the mouth. This initial chemical breakdown makes further digestion easier as food moves through the digestive system.
4.
Ans: (c)
Explanation: Bile, secreted by the liver, helps in the digestion of fats by emulsifying large fat globules into many small droplets. This increases the surface area available for fat-digesting enzymes to act on, making fat digestion more efficient. Bile itself is not an enzyme but helps the enzymes work better.
5.
Ans: (c)
Explanation: Villi are small, finger-like projections that line the inner surface of the small intestine. They greatly increase the surface area available for absorption, allowing digested nutrients (such as glucose, amino acids and fatty acids) to be absorbed quickly into the blood and lymph vessels.
B. Fill in the blanks with the correct words.
1.
Ans: The process of taking in food into the body is called Ingestion.
2.
Ans: Hydra has tentacles to draw food particles into the body.
3.
Ans: Frogs have a sticky tongue to catch their prey.
4.
Ans: Finger-like outgrowths formed by Amoeba are called Pseudopodia.
5.
Ans: Canines are present on either side of incisors.
6.
Ans: Digestion of carbohydrates begins in the Mouth.
7.
Ans: Hydrochloric acid is secreted in the Stomach.
8.
Ans: Digestive juice called bile is secreted by Liver.
9.
Ans: Sheep is an example of a ruminant.
10.
Ans: Digested food from the Abomasum passes into the small intestine.
C. Name the following.
1.
Ans: Canines
2.
Ans: Salivary Glands
3.
Ans: Liver
4.
Ans: Large Intestine
5.
Ans: Tongue
6.
Ans: Rumen
D. Answer the following questions.
1.
Ans: Nutrition is the process by which organisms take in and utilise substances required for growth, maintenance and reproduction. It involves five main stages: ingestion (taking in food), digestion (breaking food into simpler substances), absorption (uptake of soluble substances into the body), assimilation (use of these substances to build and repair tissues), and egestion (removal of undigested waste).
2.
Ans: Different animals take in food in different ways suited to their bodies and habitats:
- Amoeba uses pseudopodia to surround and engulf food particles.
- Hydra uses its tentacles to draw food into the mouth opening.
- Paramecium uses cilia (tiny hair-like structures) to sweep food into its mouth groove.
- Insects and worms have special mouth parts adapted to their diets.
- Birds use beaks shaped for the food they eat.
- Frogs catch prey with a sticky tongue.
- Snakes swallow their prey whole because their jaws allow wide opening.
- Many fishes, reptiles and mammals have teeth to bite and chew food.
3.
Ans: Amoeba is a single-celled organism that captures food using pseudopodia. When it encounters food, it extends pseudopodia to surround the particle and forms a food vacuole. Digestive juices are released into this vacuole to break down the food. The digested nutrients are then absorbed into the cell body, and undigested waste is expelled to the outside.
4.
Ans: There are four major types of teeth in humans, each with a specific function:
- Incisors: front teeth used for cutting and biting food.
- Canines: sharp, pointed teeth beside incisors used for tearing food.
- Premolars: broader teeth used for chewing and crushing food.
- Molars: large back teeth used for grinding food into smaller pieces.
5.
Ans: Digestive glands produce juices that help in digestion. The three main digestive glands in humans are:
- Salivary glands: secrete saliva to moisten food and begin starch digestion.
- Liver: produces bile that helps in the digestion and absorption of fats.
- Pancreas: secretes pancreatic juice containing enzymes that digest carbohydrates, proteins and fats.
6.
Ans: Human digestion begins in the mouth where food is ingested. Teeth break food into smaller pieces while saliva starts carbohydrate digestion. The chewed food passes down the oesophagus into the stomach, where gastric juices act mainly on proteins. Partly digested food then moves into the small intestine, where bile from the liver and enzymes from the pancreas complete digestion. Nutrients are absorbed by the small intestine and sent to body cells for use. Indigestible material passes to the large intestine where water is absorbed and waste is later egested through the rectum and anus.
7.
Ans: Most nutrient absorption occurs in the small intestine. Its inner surface has many finger-like projections called villi that increase the surface area, allowing more efficient absorption of digested nutrients into blood and lymph vessels.
8.
Ans: The liver secretes bile, which helps digest fats by emulsifying large fat droplets into many small droplets. This emulsification increases the surface area for fat-digesting enzymes to act upon, making digestion of fats more efficient.
9.
Ans: Digested nutrients are used by body cells for different purposes:
- Glucose (from carbohydrates) is used to produce energy.
- Amino acids (from proteins) are used to build and repair tissues.
- Fatty acids and glycerol (from fats) are used for energy and stored as reserves.
10.
Ans: Rumination is the process in which an animal brings back swallowed food from the stomach into the mouth to chew it again. Animals that do this are called ruminants; examples include cows, goats and deer.
11.
Ans: A ruminant's stomach has four chambers: rumen, reticulum, omasum and abomasum. Their roles are:
- Rumen: the largest chamber, stores large quantities of partially chewed food and houses microorganisms that begin digestion.
- Reticulum: works with the rumen and helps in forming cud that is brought back to the mouth for further chewing.
- Omasum: absorbs water and further grinds the food particles.
- Abomasum: the true stomach that secretes digestive juices to digest the food. Digested food from the abomasum then passes into the small intestine, where enzymes from the pancreas and bile from the liver complete digestion and most nutrient absorption takes place.
