Class 7 Science Nutrition in Animals Exam Notes

Covers following topics:

Class 7 Science Nutrition in Animals Exam Notes

Covers the following topics:

1. Holozoic Nutrition
2. Nutrition in human
3. Nutrition in a Ruminant

As animals do not have chlorophyll, they cannot prepare their own food. They obtain their food directly or indirectly from plants. Animals may be herbivores, carnivores or omnivores.

HOLOZOIC NUTRITION

In this type of nutrition, animals take in solid food such as fruits, vegetables and meat.

The five steps in the process of holozoic nutrition in animals are:

1. Ingestion
2. Digestion
3. Absorption
4. Assimilation
5. Egestion

Nutrition in Amoeba: Amoeba is a unicellular animal. It eats microscopic plants and animals that float in water. The complete process of nutrition in amoeba is as follows:

1. Ingestion: An amoeba ingests food by using its pseudopodia. When a food particle comes near an amoeba, it ingests this food particle by surrounding it with its pseudopodia. The pseudopodia close to form a small cavity called the food vacuole.
2. Digestion: The food is digested in the food vacuole by digestive enzymes.
3. Absorption: The digested food present in the food vacuole is absorbed directly into the cytoplasm of the amoeba by diffusion. The digested food just spreads out from the food vacuole into the cytoplasm of the amoeba cell.
4. Assimilation: Food absorbed by the amoeba is used to obtain energy for maintaining life processes.
5. Egestion: When a sufficient amount of undigested food collects inside the amoeba, its cell membrane suddenly ruptures at any place and the undigested food is thrown out of the cell.

Figure: The process of nutrition in amoeba

NUTRITION IN HUMAN

Nutrition in humans is holozoic. The food ingested through the mouth passes through a number of organs in our body which constitute the alimentary canal.

The alimentary canal along with the digestive glands is known as the digestive system.

The digestive system of humans consists of the following organs: mouth, pharynx, oesophagus, stomach, small intestine, large intestine, rectum and anus, along with the salivary glands, liver, gall bladder and pancreas.

Figure: Digestive system of human being (labelled illustration of the organs; not reproduced).

1. Mouth: It is a transverse slit and is also called the opening of the alimentary canal. The mouth opens into the buccal cavity.
2. Buccal cavity: The mouth opens into a cavity which contains teeth, tongue and salivary glands. Salivary glands secrete saliva which contains the salivary amylase enzyme, which converts starch into simple sugar.
3. Teeth: Teeth are hard structures held in sockets of the jaws. Teeth cut, chew and break food into smaller pieces.
4. Tongue: The tongue is the organ used for taste. It contains taste buds to distinguish whether a type of food is sweet, sour, bitter or salty (see figure). It also helps in rolling and pushing the food into the pharynx. It mixes the saliva with the food and also helps us in speaking.

Figure: Tongue and its taste zones

1. Oesophagus or Food pipe: It is a connecting tube between the mouth and the stomach. The food is pushed down towards the stomach by the movement of the muscles of the food pipe.
2. Stomach: The stomach is a J-shaped bag-like structure made of muscles. The stomach secretes gastric juice and hydrochloric acid. Hydrochloric acid kills microorganisms and provides an acidic medium for effective digestion. In the stomach the food is thoroughly mixed with the gastric juice secreted by the gastric glands present in the stomach. The gastric juice contains an enzyme called pepsin which helps to break down proteins into simpler substances.
3. Small Intestine: It is a coiled tube and is about 7 metres in length. It consists of three parts, namely duodenum, jejunum and ileum. In the small intestine the food is mixed with bile juice and pancreatic juice. These are secreted by the liver and the pancreas, respectively. Bile juice breaks down fats into fatty acids and glycerol. The pancreatic juice breaks down starch into simple sugar and proteins into amino acids. Digestion of all the components of food gets completed here and the end products are ready for absorption.
   Absorption of food occurs through millions of small projections in the inner walls of the part of the small intestine called the ileum. These projections are known as villi. The incorporation of absorbed nutrients into the cell components is called assimilation.
   The food that remains undigested and unabsorbed then enters the large intestine.
4. Large intestine: It is the last organ of the digestive system. It is about 1.5 m in length. It consists of three parts, namely caecum, colon and rectum. It helps in absorbing water and in removing undigested solid wastes from the body in the form of faeces through an opening called the anus.
5. Anus: It is the last part of the alimentary canal. Its main function is to expel solid faeces out of the body.
6. Digestive Glands:
   1. Salivary Glands: There are three pairs of salivary glands located in the mouth. Salivary glands secrete saliva which contains the amylase enzyme. Amylase works on starch and converts it into simple sugar.
   2. Liver: It is a reddish brown gland and is located in the upper part of the abdomen. It secretes bile juice that is stored in the gall bladder. The bile helps in breaking down fat into simpler substances.
   3. Pancreas: It is a cream-coloured gland and is located just below the stomach. It secretes pancreatic juice into the small intestine. It acts on carbohydrates and proteins and converts them into simpler substances.

Figure: Movement of the food in the oesophagus

NUTRITION IN A RUMINANT

A ruminant is a herbivorous animal which regurgitates its food and digests it in steps. For example: cow, goat, sheep etc.

The 2 steps involved in the digestion of ruminants are:

1. The ruminant first eats the food and regurgitates a semi-digested food called cud.
2. The ruminant then eats the cud when at rest. This process of eating the cud is called ruminating.

Ruminants have a special stomach with 4 chambers, which are as follows:

1. Rumen: This is the largest chamber of the stomach. It is mainly used for storing food.
2. Reticulum: It helps in moving the food back to the mouth when needed.
3. Omasum: This is the smallest chamber of the stomach. Its main function is to absorb excess water.
4. Abomasum: This is the true stomach where gastric juices are secreted to help digestion. Here the food is digested just like in the human stomach.

Digestion of food in ruminants:

Ruminants mostly eat grasses and leaves which are rich in cellulose. Ruminants can digest cellulose because cellulose-digesting bacteria and protozoa are present in their stomach.

Figure: Four chambered stomach of a cow (ruminant): labelled illustration showing mouth, salivary glands, oesophagus, rumen, reticulum, omasum, abomasum, liver, pancreas, small intestine, caecum, large intestine and anus (not reproduced).

Half-chewed grass travels from the mouth to the first chamber of the stomach, called the rumen, where it is acted upon by bacteria and microorganisms. It then goes into the reticulum, from where it is returned to the mouth as cud for thorough chewing, called rumination. It enters a third chamber called the omasum. Here it is broken down into still smaller pieces. Finally, it enters the fourth chamber called the abomasum where enzymes act upon it and digestion is completed. It is finally sent to the small intestine where the absorption of the nutrients takes place.

(i) Mouth : It is a transvers slit & also called opening of alimentary canal. Mouth opens into buccle cavity.

A ruminant is an herbivours animal which regurgitates its food & digest it in step. For example- Cow, goats, sheep etc.

Question. Some carbohydrate-rich foods, like bread, can be digested almost immediately to glucose. Others, like brown rice, are digested much more slowly. Foods that quickly get digested to glucose are said to have a high glycemic index. Which of these conclusions can be correctly drawn from the table showing high and low glycemic foods?

(a) Cereals are high glycemic foods
(b) Fruits are low glycemic foods
(c) Processed foods are high glycemic foods
(d) Foods made from rice are low glycemic foods

Answer : C

Question. The list below gives the items that Sam decided to have for his dinner: 1. Curry with beans and spinach (palak), 2. Salad with raw fruits and vegetables like carrot and beetroot, 3. Curd, 4. Sprouted moong dal. From the food items given below, what should Sam add to have a balanced diet for his dinner?
(a) Curry with cauliflower
(b) Chapatti
(c) Onion pakoda
(d) Butter milk

Answer : B

Question. Water is removed from foods because dried foods can be stored for longer periods without getting spoilt. The graphs given below show the water content originally in four different foods. Water was almost completely removed by passing dry air through each of these four foods. If the weight of each of them after that was 50 grams, which one was the heaviest to start with?

(a) Cucumber
(b) Apple
(c) Bread
(d) Butter

Answer : A

Question. In which part of the digestive system does a piece of bread which is eaten get completely broken down into simple sugars?
(a) Stomach
(b) Liver
(c) Large intestines
(d) Small intestines

Answer : B

Question. Given below is a label found on a food item. 
Study it and answer the question.
On which of the following food items may this food label be found?

(a) oil bottle
(b) milk container
(c) salt packet
(d) bottle of cola

Answer : B

Question. Given below is a label found on a food item. 
Study it and answer the question.
Which nutrient is NOT provided by the food item having the above label?

(a) Calcium
(b) Vitamin A
(c) Sugars
(d) Iron

Answer : D

Question. Which of the following could be 'X' in the table below?

(a) Ground nut
(b) Mango
(c) Flax
(d) Coconut

Answer : D

Question. What is dry cleaning" of clothes?"
(a) putting out the clothes to dry in the sun
(b) using a liquid other than water to clean
(c) using water vapour to clean the clothes
(d) using warm air to clean the clothes

Answer : B

Question. The figure shown here represents which of the following processes?

(a) Reproduction
(b) Metamorphosis
(c) Food chain
(d) Adaptation

Answer : B

Question. Study the containers P, Q, R, and S shown below. The temperature of the water in each container is recorded every minute. This experiment is studying the variation in the temperature of water over time for different …..

(a) shapes of the container
(b) intensities of the burner
(c) volumes of water heated
(d) exposed surface areas

Answer : C

Question. The maximum and minimum temperature during a 24 hour period in four cities A, B, C and D are shown below. Which of the following is likely to be in or nearest to a desert?

City	Maximum	Minimum
A	42oC	35
B	39oC	18oC
C	25oC	18oC
D	20oC	18oC

(a) A
(b) B
(c) C
(d) D

Answer : B

Question. Materials expand upon heating. How much a material expands upon heating is given by its coefficient of expansion. There are three metals P, Q and R. Of them, P has the largest coefficient of expansion, and R has the smallest. When a thermostat is made with P and  R, this is the shape it takes when heated: Three pieces of P, Q and R are fused together as shown . What shape will it take when heated?

Answer : A

Question. The specific heat capacity of a substance is the amount of heat required to raise the temperature of 1kg of the substance by 10C. The specific heat capacities of a few substances are also given here. Using this information, answer the question….
For STORING thermal energy in solar heating systems, we would need a material that retains heat the longest. Which of these would be most suited

Substance	Specific heat (J/Kg' C x 1000)
Water Vegetable oil Kerosene Alcohol Aluminum Copper Iron Lead	4.18 1.96 2.11 2.40 0.90 0.38 0.53

(a) Aluminum
(b) Water
(c) Copper
(d) Iron

Answer : B

Question. The specific heat capacity of a substance is the amount of heat required to raise the temperature of 1kg of the substance by 10C. The specific heat capacities of a few substances are also given here. Using this information, answer the question .If equal masses each of water, vegetable oil, aluminium and copper are heated uniformly for five minutes, which one of them will record the maximum rise in temperature?

Substance	Specific heat (J/Kg' C x 1000)
Water Vegetable oil Kerosene Alcohol Aluminum Copper Iron Lead	4.18 1.96 2.11 2.40 0.90 0.53 0.13

(a) Water
(b) Vegetable oil
(c) Aluminium
(d) Copper

Answer : D

Question. The boiling point of water is 1000C at sea level. The boiling point of butane is -1.50 C. If we leave liquid butane in a bowl on a table in a room where the temperature is 240C, butane will -
(a) Evaporate
(b) Condense
(c) Freeze
(d) Melt

Answer : A