Complete Guide For Class 7 Science Chapter 2: Nutrition in Animals

Welcome to iPrep, your Learning Super App. Our learning resources for the chapter, Nutrition on Animals in Science for Class 7th chapter 2 are designed to ensure that you grasp this concept with clarity and perfection. Whether you’re studying for an upcoming exam or strengthening your concepts, our engaging animated videos, practice questions and notes offer you the best of integrated learning with interesting explanations and examples. 

While plants can create their food through photosynthesis, animals must consume other organisms to meet their nutritional needs. This process is essential for their growth, repair, and overall functioning. Let’s learn more about this in our chapter ‘Nutrition in Animals’.

Why Do Animals Need Food?

Nutrition in animals starts with understanding why animals need food. All organisms, including humans, require food for:

• Growth
• Repair
• Functioning of the body

Components of Food

When it comes to nutrition in animals, there are various components involved. Those various essential components include :

• Carbohydrates
• Fats
• Proteins
• Vitamins
• Minerals
• Roughage

Digestion

Another significant part of nutrition in animals is Digestion. Digestion is the process of breaking down complex food substances into simpler forms so that they can be used by the body. This process is crucial because the food we eat is too complex to be utilized directly.

Different Ways of Taking Food

The chapter nutrition in animals discussed different ways of taking foods. Different organisms have unique ways of obtaining food:

• Bees and Hummingbirds: Suck nectar from flowers.
• Infants of Humans and Many Mammals: Breast-feed from their mothers.
• Snakes (e.g., Python): Swallow whole prey.
• Aquatic Animals (e.g., Octopus): Filter food from the surrounding water.

Examples of Feeding

Nutrition in animals also covers various examples of Feeding. These are:

• Hummingbird: Sucking nectar from flowers.
• Python: Swallowing prey whole.
• Octopus: Grabbing floating food in water.
• Starfish: Feeding on hard-shelled animals by eviscerating its stomach into the shell.

The Human Digestive System

When understanding nutrition in Animals, it is important to understand the human Digestive system. The human digestive system is a complex network designed to break down food and absorb nutrients.

Alimentary Canal

The alimentary canal is a tube running from the mouth to the anus and includes the following parts:

1. Buccal Cavity
2. Food Pipe (Oesophagus)
3. Stomach
4. Small Intestine
5. Large Intestine
6. Rectum
7. Anus

Mouth and Buccal Cavity

The chapter Nutrition in Animals further covers the Mouth and Buccal Cavity which involves.

• Ingestion: The process of taking food into the mouth.
• Teeth: Break down food into smaller particles. Types of teeth:
  • Incisors: Biting and cutting.
  • Canines: Gripping and tearing.
  • Premolars: Chopping and grinding.
  • Molars: Grinding and crushing.

• Salivary Glands: Secrete saliva that begins the digestion of carbohydrates.
• Tongue: Helps mix, taste, and swallow food.

We can conclude that:

• Food is taken into the body through the mouth.
• The process of taking food into the body is called ingestion.
• Teeth present in the mouth break down the food into smaller particles and help in mixing them mechanically.
• Salivary glands secrete saliva which helps in converting complex sugar into simple sugar.
• The tongue helps in mixing, tasting, and swallowing food.

Activity: Testing the Effect of Saliva

Let’s now do an activity to better understand the concept of nutrition in animals.

• Test Tubes Preparation:
  • Test Tube A: Boiled rice.
  • Test Tube B: Boiled rice chewed for 3-5 minutes.
  • Add iodine solution to both and observe.
• Result: Test Tube A turns blue/purple; Test Tube B does not change color, indicating the breakdown of starch into sugars by saliva.

Position of taste buds on the tongue 

Different taste buds detect different tastes of food. 

Activity to check the taste buds 

1. Prepare samples for each of:

i) Sugar solution

ii) Common salt solution

iii) Lemon juice

iv) Juice of crushed neem leaf or something bitter like bitter gourd.

 2. Blindfold one of your class friends and ask him/her to take out the tongue and keep it in a flat position. 

3. Take fresh toothpicks to put the different samples on his/her tongue. Use a new toothpick for each sample.

 4. Observation: Ask the friend to point out which area is tasting which taste on the tongue as shown in the figure above. 

Digestion in the Alimentary Canal

• Oesophagus: Transports food to the stomach via peristalsis (wave-like muscle contractions).

• The swallowed food moves through the esophagus by peristalsis. This runs along the neck and chest.
• Food is pushed down by movement of the wall of the food pipe. Such movements by the wall of the alimentary canal to push the food in the forward direction, are called peristalsis.
• Sometimes the food is not accepted by the walls of the alimentary canal and is vomited out.
• HCl from the stomach kills many bacteria coming along with the food. It also provides the acidic medium to the stomach required for the chemical reactions.
• The digestive juices break down the proteins into simpler components.
• The mucous protects the lining of the wall of the stomach.

Stomach

• Thick-walled muscular bag.
• Secretes HCl, mucous, and digestive juices.
• Begins the breakdown of proteins.

Small Intestine

• Length: About 7.5 meters.
• Functions:
  • Receives bile from the liver and pancreatic juice from the pancreas.
  • Completes digestion of carbohydrates, proteins, and fats.
• Absorption: Nutrients are absorbed through villi into the bloodstream.
• Liver: a reddish brown gland situated in the upper part of the abdomen on the right side. It secretes bile juice, which helps in the breakdown of fats. Bile is stored in a sac-like structure called the gallbladder.
• Pancreas: a large creamy-coloured gland located just below the stomach. It secretes pancreatic juice, which acts on carbohydrates and proteins to convert in simpler forms.
• The partly digested food reaches the lower part of the small intestine, where the intestinal juice completes the digestion of all digestible components.

Absorption of Digested Food

• Absorption occurs in the small intestine with the help of villi, which increases the surface area for absorption.
• The absorbed nutrients are transported via blood vessels to different body organs, where assimilation occurs.

Large Intestine

• Length: About 1.5 meters.
• Functions:
  • Absorbs water and salts.
  • The waste in the form of semi-solid remains in the rectum. This waste in the form of feces is removed through the anus.
  • This process of removal is called egestion.

The entire digestion process looks like this:

Mouth (Ingestion) –> Oesophagus (Peristalsis) –> Stomach (HCl and digestive juices) –> Small Intestine (Pancreatic and bile juices) –> Absorption in Villi –> Large Intestine (Water absorption) –> Rectum (Waste storage) –> Anus (Egestion)

Summary Table of Digestive Juices and Their Actions

Digestive Juice	Source	Action
Saliva	Salivary glands	Converts complex sugars into simple sugars
Bile	Liver	Breaks down fats into smaller fat globules
Pancreatic juice	Pancreas	Acts on carbohydrates and proteins
Intestinal juice	Small intestine	Completes the digestion of all digestible components

Unique Digestion in Grass-Eating Animals

Rumination in Ruminants

The chapter nutrition in animals also covers Rumination. Ruminants like cows and buffaloes have a rumen, where partially digested food (cud) is stored and later chewed.

They have a sac-like structure between the small and large intestines for digesting cellulose with the help of microbes. Therefore, to summarize-

• Rumen: A special stomach chamber where the grass is partially digested.
• Cud: The regurgitated and re-chewed food.
• Process: Cud returns to the mouth for further chewing.
• In this sac, the cellulose of the food is digested by the action of microbes present in cattle. Such microbes or bacteria are not found in human beings. This is why humans are not able to digest the cellulose of the food.

Amoeba

Nutrition in animals also covers, nutrition in Amoeba.

• Amoeba is a microscopic unicellular organism found in pond water.
• Its single-celled body is covered by a cell membrane.
• Inside the cytoplasm, there is a round nucleus and many bubble-like sacs called vacuoles.
• It can change its body shape by forming pseudopodia, which are a kind of false foot in the form of finger-like projections. These pseudopodia help the amoeba in taking up food and changing its position.

Feeding in Amoeba

Amoeba is a single-celled organism with unique feeding methods:

• Amoeba feeds on microscopic bits of food from its surroundings.
• Whenever it senses the food, it stretches out its pseudopodia around the food, like a cup.
• Food is engulfed in a food vacuole.
• Once the food is in a food vacuole, the digestive juices are secreted. These juices break down the complex molecules into simpler ones.
• The broken and simplified food in the body of the amoeba is absorbed.
• The absorbed food in the cytoplasm is utilized for growth, maintenance, and multiplication.
• The absorbed food on oxidation in the cytoplasm releases energy for the movement of the body and other activities.
• The vacuole also helps in expelling out the undigested food.

In conclusion, Class 7 Science Chapter 2 – Nutrition in Animals provides a comprehensive understanding of how animals, including humans, obtain, process, and utilize food for their survival. From the breakdown of complex food substances in the digestive system to the unique feeding habits of different organisms like amoeba and ruminants, this chapter covers essential concepts that highlight the diversity of nutritional strategies in the animal kingdom.

The study of Nutrition in Animals not only deepens our understanding of biological processes but also underscores the vital role of nutrition in maintaining life. By mastering the content of Class 7 Science Chapter 2 – Nutrition in Animals, students are well-equipped to appreciate the intricacies of animal biology and apply this knowledge in their academic journey. Remember, Nutrition in Animals is a key concept that lays the foundation for future studies in biology, making this chapter crucial for building a strong scientific understanding.