Class 7 Science Nutrition in Animals Notes

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Revision Notes for Class 7 Science Chapter 2 Nutrition in Animals

Class 7 Science students should refer to the following concepts and notes for Chapter 2 Nutrition in Animals in Class 7. These exam notes for Class 7 Science will be very useful for upcoming class tests and examinations and help you to score good marks

Chapter 2 Nutrition in Animals Notes Class 7 Science

Nutrition in Animals

Animals are heterotrophs. They obtain food from green plants or animals that feed on plants.
 
Herbivorous Animals: They feed only on plants or plant parts. Examples. Cow, buffalo, goat, deer, rabbit, horse and elephant.
 
Carnivorous Animals: They feed on the flesh of other animals. Examples: Lion, Tiger and Leopard.
 
Omnivorous Animals: They feed on both plants and animals. Examples: pig, man, cockroach.
 
MODES OF NUTRITION IN ANIMALS

The mode of nutrition in herbivorous, carnivorous or omnivorous animals is called holozoic nutrition. However, some animals are parasites, saprophytes or scavengers.
 
i) Parasitic animals obtain food and shelter form the host. They may be endoparasites or ectoparasites.
 
Endoparasites live inside the host body and derive nutrients from the hosts body fluid blood or tissue. Examples: Malarial parasites live in RBCs, flat worms and round worms reside in liver or intestine.
 
Ectoparasites such as ticks, mites, body louse and bed bugs cling on the body surface of their hosts and suck their blood.
 
ii) Saprophytic animals feed on dead and decaying organic matter. Earthworms are saprophytes.
 
iii) Scavengers feed on decaying animals. Vulture, crow and jackal are scavengers.
 
PROCESS OF HOLOZOIC NUTRITION

In holozoic nutrition, animals take solid food. Their food contains insoluble complex nutrients. The body can use these nutrients only when these are digested and broken down into simple soluble molecules. The soluble molecules are then absorbed by the intestinal wall.
 
The process of holozoic nutrition, involves the following steps. Ingestion, digestion, absorbtion, assimilation and egestion.
 
Ingestion

It is the process of taking in the food items from outside into the body through mouth. Different organisms have different methods of food intake and their food habit also vary. The organ involved in the food intake, i.e., the mouth varies from lowest animals (protozoans) to highest animals (mammals). The mouth part of animals are modified to enable them to catch their prey or procure food. For example:
 
Unicellular Amoeba engulfs tiny particles of food by surrounding it with false feet or pseudopodia. The pseudopodia then join together to form a small cavity, a food vacuole (Fig.1).
Class 7 Science Motion and Time Advanced Notes
Class 7 Science Motion and Time Advanced Notes
 Spider weave a sticky web in which small insects get stuck.
 An earthworm uses its muscular pharynx to swallow its food.
 Human beings use their hands to put food into their mouths.
 
Digestion

The food that we take in is normally solid and complex. The cells of the body cannot use their solid food. All living organisms, except parasites must digest their food to get energy. Thus, the process of breakdown of complex food molecules into simpler forms is called digestion. Most animals use both physical and chemical methods for digesting food. Enzymes are the biocatalyst, secreted by glands found in the digestive system.
 
Enzymes help in the breakdown of complex molecules like carbohydrates, proteins fats etc. into simple molecules.
 
Digestion in lower animals like Amoeba, Paramoecium is generally intracellular (within the cell) as the food is digested inside the food vacuole and the digestive enzymes are secreted by the cell itself.
 
The higher animals like frogs humans, etc., the food passes through the alimentary canal and the digestion occurs in its lumen on. In animals with well developed organs and organ systems, digestion is extracellular (outside the cell). Various digestive enzymes are mixed with the food as it passes through the alimentary canal. Examples are saliva in mouth and gastric juices in the stomach.
 
Hydra is a multicellular organism, where digestion is extracellular (outside the cell) as well as intracellular (in the cells of the inner layer).
 
Absorption

The digested food mixes in the body fluid the blood of the animal and gets absorbed. In unicellular organisms like Amoeba, the absorption occurs in the cytoplasm. In Hydra, absorption of food occurs by diffusion of digested food through the cells lining the body cavity. In higher organisms (man), absorption of food occurs in the small intestine.
 
Assimilation

The process of conversion of absorbed food into living protoplasm is called assimilation. The food absorbed by the body is used as a fuel to produce energy from glucose by respiration for carrying out different life process as like growth, development, etc. Proteins are the building blocks of our body and help in making new tissues as well as repairing worn out tissues.
In case of Amoeba and Paramoecium assimilation of food occurs through streaming movements of protoplasm inside the body cavity. In Hydra, food is assimilated inside the cells.
 
Egestion

The process of removing undigested solid food parts from the body in the form of faces is called egestion.
 
In Amoeba, when sufficient amount of undigested food collects inside the body cavity, its cell membrane can rupture at any place to throw out the undigested food.
 
In Hydra, the waste materials are thrown out through the single body cavity that works both as mouth and anus.

DIGESTION IN HUMANS

Humans have a well developed digestive system. This consists of the gut or alimentary canal, along with the associated digestive glands.

Parts of alimentary canal and accessory glands

The food that we take in can provide energy only if it is digested, absorbed and assimilated to be distributed to all parts of the body.

During digestion large insoluble pieces of food are broken down into soluble substances which are small enough to be absorbed through the walls of the intestine and into the bloodstream. This, process involves certain physical and chemical reactions, as follows:

Class 7 Science Nutrition in Animals Advanced Notes_1

Physical Action

• Chewing the food with teeth, so as to break the solid food into smaller pieces.

• Churning by the stomach to mix the food with the gastric juices.

Chemical Action

• Carbohydrates to simple sugars.

• Fats to fatty acids and glycerol

• Proteins to amino acid.

Enzymes are the digestive juices prepared by cells in various part of the digestive system. Table 1. Lists the details of the source, their substrates, affects and the resultant products.

The alimentary canal is a long tube of varying diameter which begins from the mouth and ends at the anus. It consists of mouth, pharynx, oesophagus, stomach, small intestine, large intestine, rectum and anus.

Mouth: Food is ingested by us through the mouth. The mouth contains tongue, teeth and salivary glands. They work together in chewing (masticating) the food. The chewed food is mixed with saliva, a watery fluid secreted by the salivary glands. This process is called mastication. Saliva contains the enzyme amylase, which converts starch into sugar, so it tastes sweet to us.

Class 7 Science Nutrition in Animals Advanced Notes_2

TeethOur teeth cut, tear and grind the food before we swallow it. We can feel the different shapes of our teeth with our tongue. There are four types of teeth in our mouth.

a) Incisors: These are the front 8 teeth, four on upper and four on lower jaw. These are flat, chisel - shaped teeth, well adapted for cutting and biting of food item

b) Canines: One incisor each is found on either side of each jaw. These round, sharp and pointed teeth are well adapted to hold and tear the food.

c) Premolars: There are two premolars on each side of each jaw. They have flat surfaces bearing small grooves and ridges, and are well adapted to crush and grind food.

d) Molars: These are the last three teeth on both sides in both the jaw They have almost flat surfaces with small projections for effective grinding of the food. (Fig. 7)

The white substance that covers our teeth is called enamel. It is the hardest substance in the body. All of us have two sets of teeth in our lifetime. The first set erupts when we are babies and lasts until we are about 8 years old. These are known as the milk teeth or temporary teeth. A child has only 20 such teeth –10 in each jaw. These teeth fall out one by one and are replaced by permanent teeth. A human adult has 32 teeth in all –16 in each jaws.

Structure of a tooth: Each tooth remains buried in the jaw bone by its root and the crown remains outside the gum. Incisors and canines have single root, while premolars and molars have two roots each. The crown is formed of dentine and has a layer of enamel outside.

Class 7 Science Nutrition in Animals Advanced Notes_3

Enamel forms the shining white part of the crown of each tooth. It is deposited on the surface of crown of the tooth.

Enamel is the hardest substances in our body, even harder than bones. It is also chemically the most stable substance. (Fig. 8).

Tongue: The tongue is a muscular organ and helps to mix saliva in the food. It pushes food towards our teeth. The tongue rolls the food into a bolus which is easy to swallow. It is pushed down the food pipe or oesophagus, by means of a series of rhythmic muscular contractions that go by the name ‘peristalsis’.

Class 7 Science Nutrition in Animals Advanced Notes_4

The tongue is the main organ of taste. Different sets of taste buds located in specific areas of the tongue, distinguish whether the food is sweet, salty, sour, bitter, etc. Thus, taste buds help us to select the right quality of food. The tongue also helps us to speak

Oesophagus: It is the tube connecting the mouth and the stomach, and is about 30 cm long. It takes about six second for solid food to reach the stomach after it is swallowed. Liquids travel faster down the oesophagus.

The powerful muscles in the oesophagus gently push food down to  the stomach in a wave like action, called peristalsis as mentioned earlier.

Stomach: It is a J-shaped muscular bag. It can hold upto two litres of food at a time. Food stays in the stomach from a few minutes to a few hours depending on the type of food. Gentle movements of the stomach wall churn the food up with digestive juices like hydrochloric acid and gastric juices and change it into a semi-liquid state called chyme. The enzymes present in the gastric juices break down proteins. The hydrochloric acid kills the harmful bacteria and also helps the enzymes to work. In the stomach, the milk is changed to curd. Thus, food gets partly digested in the stomach.

Sometimes, we experience vomiting. It is nothing but antiperistaltic movements of the stomach wall and oesophagus.

 

Q1.What is nutrition?

A. The process by which living beings take in food and use it to obtain energy for growth and development is called nutrition

Q2.Why do we call animals heterotrophs?

A. Animals are called heterotrophs as they do not prepare their own food and derive their nutrition from some other organisms.

Q3.Mention 5 steps in the process of animal nutrition.

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

Q4. Name three glands associated with the alimentary canal in man. Mention their secretions.

A. 1. Salivary glands- secrete digestive juice that digests starch.

B. Liver- secretes bile juice.

C. Pancreas- secretes digestive juices that digest carbohydrates and proteins.

Q5.What is ingestion?

A. The process of taking in of food is called ingestion.

Q6. Name different types of teeth in our mouth and write their functions.

A. 1. incisors- cutting and biting

2. canines- tearing

3. pre molars- crushing and grinding

4. molars- finer grinding

Q7.Why is not advisable to not to talk while swallowing food?

A. When we talk while eating our wind pipe is open and food can enter in it leading to choking and hiccupping.

Q8.What are the secretions in stomach and their role in nutrition process?

A. It secretes- 1. HCl- provides acidic medium and kills microorganisms.

2. mucous- protects stomach lining from the action of acid and lubricates food.

3. Digestive juice- digests proteins.

Q9.What happens to food in small intestine?

A. 1. Small intestine receives digestive juices from pancreas, liver and its own wall.

2. Bile from liver emulsifies fats.

3. Pancreatic and intestinal juices break down carbohydrates, fats and proteins.

4. Nutrients are absorbed.

Q10. How is digested food absorbed?

A. Absorption of food occurs through small projections in the inner lining of the part of small intestine. These projections are called Villi.

Q11. What is large intestine and how does it function?

A. It is the extension of small intestine in the alimentary canal with a wider diameter. It helps in reabsorption of water from the waste to be thrown out.

Q12. Explain the process of digestion in ruminants.

A. cattle animals quickly swallow their food and store it in a part of stomach called Rumen. The food gets partially digested there called Cud. This cud returns to the mouth for further chewing and the process is called rumination. Their food is rich in cellulose which is digested in caecum.

Q13. What are the products of digestion of carbohydrates, fats and proteins?

A. the products of digestion of carbohydrates, fats and proteins are glucose, fatty acids and glycerol and amino acids respectively.

Q14. Although large intestine is not involved in the process of digestion, yet it has an important function. Justify.

A. It helps in absorption of water.

Q15. Write a note on the nutrition of amoeba.

A. Amoeba ingests food by pseudopodia and traps food in a vacuole. Food is digested with the help of digestive juices within it. The undigested food is thrown out by the vacuole only.

Q16. What is egestion?

A. it is the process of throwing out of undigested food.

Q17. What is the role of gall bladder in human digestive system?

A. gall bladder stores the secretion of liver temporarily.

Q18. Why are cattle animals known as ruminants?

A. They are called so as the partially digested food comes back in the miuth for further chewing.

Q.19: What is mastication?

Ans: Mastication is a process in which chewing of food and mixing of saliva with it is done in mouth.

Q.20: What is the role of tongue in our mouth? Ans: The tongue has following roles in our mouth:

=> It helps in talking.

=> It helps in mixing of saliva with the food during mastication.

=> It helps to swallow the food.

=> It gives us sensation of taste of food.

Q21: What is peristalsis?

Ans: The powerful muscles in oesophagus gently push food down to the stomach in a wave - like action, called peristalsis.

Q.22 What are secreted inside the stomach?

Ans: Gastric juice is secreted by the walls of stomach which contains HCl and Pepsin.

Q.23 What are the functions of HCl stomach?

Ans:Functions of HCl:

=> It helps to kill the germs present in the food.

=> After mixing with the food it makes an acidic medium which is essential for the activation of digestive juice.

Q.24 What is secreted from liver?

Ans: Bile juice is secreted from liver.

Q.25 What is digestion?

Ans: Digestion is a process which include crushing of the food into smaller particles by chewing and then breakdown of its complex components into simpler substances with the help of enzymes in a liquid medium which can be absorbed by our body.

Q.26: Write short notes (1 or 2 sentences) on -

(a) Pancreas (b) Liver (c) Oesophagus (d) Rumination (e) Pseudopodia

Ans:

(a) Pancreas: Pancreas is a large cream coloured gland located or present just below the stomach. Pancreatic juice acts on carbohydrates and protein and changes them into simpler forms.

(b) Liver: Liver is a reddish brown gland present in the upper part of our abdomen on the right side. It is the largest gland in our body. It secretes bile juice stored in sac - like structure called gall bladder.

(c) Oesophagus: It is along, narrow, muscular tube which directly leads to the stomach. It is about 25 cm long and passes downwards through the neck, the thorax and the abdominal cavity.

(d) Rumination: A process in which partially digested food returns to the mouth in small lumps and the animal chews it. This type of process is called Remination or Ruminatioand such types of animals are called Ruminants.

(e) Pseudopodia: The unicellular organism like amoeba constantly changes its shape and position. It catches food by pushing out a finger - like projection called Pseudopodia.

Q.27: What are digestive enzymes?

Ans: There are different types of enzymes which are used for the digestion of different food materials like - carbohydrates, fats, protein etc into their usable form.

Q28. Draw a labeled diagram of human digestive system.

A.

CBSE Class 7 Science - Nutrition in Animals

Please click the link below to download pdf file for  Class 7 Science Nutrition in Animals Advanced Notes

Chapter 01 Nutrition in Plants
Class 7 Science Nutrition in Plants Notes
Chapter 02 Nutrition in Animals
Class 7 Science Nutrition in Animals Notes
Chapter 03 Fibre to Fabric
Class 7 Science Fibre to Fabric Notes
Chapter 05 Acids, Bases and Salts
CBSE Class 7 Science Acids Bases and Salts Notes
Chapter 06 Physical and Chemical Changes
CBSE Class 7 Science Physical And Chemical Changes Notes
Chapter 07 Weather, Climate and Adaptations of Animals to Climate
Class 7 Science Weather Climate Adaptations of Animals to Climate Notes
Chapter 08 Winds, Storms and Cyclones
Class 7 Science Winds Storms and Cyclones Notes
Chapter 11 Transportation in Animals and Plants
Class 7 Science Transportation in Animals and Plants Notes
Chapter 12 Reproduction in Plants
Class 7 Science Reproduction in Plants Notes
Chapter 13 Motion and Time
Class 7 Science Motion and Time Notes
Chapter 14 Electric Current and its Effects
Class 7 Science Electric Current and its Circuits Notes
Chapter 17 Forests: Our Lifeline
Class 7 Science Forests Our Lifeline Notes
Chapter 18 Wastewater Story
Class 7 Science Waste Water Story Notes

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