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Nutrition in Animals Class 7 Notes Science Chapter 2

Introduction

  • Plants can undergo photosynthesis to produce their own food, unlike animals.
  • Animals derive their food from plants either directly or indirectly through other animals.
  • Some animals have diets that consist of both plants and animals.
  • All organisms, including humans, need food for growth, repair, and bodily functions.

Nutrition in Animals Class 7 Notes Science Chapter 2

  • Animal nutrition involves nutrient requirements, food intake methods, and utilization in the body.
  • Components of food, such as carbohydrates, are complex and need to be broken down into simpler substances for utilization.
  • The process of breaking down complex food components into simpler substances is known as digestion.

Different Ways of Taking Food

Each species or type of organism has their own way of taking in food. Bees and hummingbirds suck plant-nectars, infant of humans and some animals feed on mother’s milk, Snakes such as python consume the animals upon which they prey. Aquatic animals filter small food particles floating close by and feed on them.

All organisms have their unique ways of consuming food, tailored to their physiology. These methods include:

  • Chewing: This involves biting and grinding food using teeth within the mouth. Examples include humans and dogs.
  • Scraping: Here, an organ like the jaw scrapes food off a surface. Examples are seen in snails and ants.
  • Syphoning: Food is absorbed into the mouth. Butterflies use this method.
  • Capturing and swallowing: This involves seizing food and then swallowing it whole. Lizards are an example.
  • Sucking: Organisms pierce food and draw out liquid. Mosquitoes utilize this method.
  • Sponging: Saliva combines with food to dissolve it in the mouth. Houseflies demonstrate this approach.

Digestion in Humans

Food ingestion process in humans:

  • Food is taken in through the mouth and utilized.
  • Unused parts of the food are defecated.

Structure of the human alimentary canal: The alimentary canal is a continuous passage starting from the buccal cavity and ending at the anus. Compartments of the alimentary canal include:

  • Buccal cavity
  • Foodpipe or esophagus
  • Stomach
  • Small intestine
  • Large intestine terminating in the rectum
  • Anus
  • These parts collectively form the digestive tract.

Digestion process along the alimentary canal:

  • Food components gradually get digested as they move through different compartments.
  • Inner walls of the stomach and small intestine, along with associated glands like salivary glands, liver, and pancreas, secrete digestive juices.
  • Digestive juices convert complex food substances into simpler ones.
  • The digestive tract and associated glands constitute the digestive system.

Human Digestive SystemHuman Digestive System

The Mouth and Buccal Cavity

  • The process of ingesting food begins with the mouth, where food is taken in.
  • Teeth play a crucial role in masticating food into small pieces through mechanical breakdown.
  • Each tooth is anchored in a distinct socket within the gums and serves different functions.

Nutrition in Animals Class 7 Notes Science Chapter 2

  • Two sets of teeth are present in humans: milk teeth, which are shed during childhood, and permanent teeth, which replace them.
  • Saliva aids in breaking down starch into sugars, facilitating digestion.
  • The tongue, a muscular organ in the buccal cavity, assists in speech, mixing food with saliva, swallowing, and tasting different flavors.

Sweets and Tooth Decay

  • Bacteria naturally present in the mouth are typically not harmful. If oral hygiene is neglected after eating, harmful bacteria can thrive by breaking down sugars from leftover food, releasing acids that gradually damage teeth. 
  • This process, known as tooth decay, can lead to severe toothache and, in extreme cases, tooth loss. 
  • Major culprits of tooth decay include chocolates, sweets, soft drinks, and other sugar-laden products.

The Foodpipe/Oesophagus

  • The food pipe, also known as the esophagus, is where swallowed food travels into the stomach.
  • The food pipe is located along the neck and the chest.
  • Food is propelled downwards in the food pipe by the contractions of its walls.
  • This movement of pushing food downwards occurs throughout the entire digestive tract.
  • At times, when the stomach rejects food, it can lead to vomiting.

The Stomach

  • The stomach is a thick-walled organ shaped like a flattened J and is the widest part of the alimentary canal.
  • Food enters the stomach from the esophagus and exits into the small intestine.
  • The inner lining of the stomach produces mucus, hydrochloric acid, and digestive juices.
  • Mucus protects the stomach lining, while hydrochloric acid aids in killing bacteria and creating an acidic environment for digestion.
  • Digestive juices in the stomach help break down proteins into simpler substances.

Question for Chapter Notes: Nutrition in Animals
Try yourself:
Which part of the alimentary canal is responsible for the digestion of fats?
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The Small Intestine

  • The small intestine is approximately 7.5 meters long and highly coiled.
  • It receives secretions from the liver, pancreas, and its own walls.
  • The liver, a reddish-brown gland in the upper right abdomen, is the largest gland in the body. It secretes bile juice stored in the gall bladder, crucial for fat digestion.
  • The pancreas, a large cream-colored gland beneath the stomach, produces pancreatic juice that aids in breaking down carbohydrates, fats, and proteins into simpler forms.
  • In the lower part of the small intestine, intestinal juice completes the digestion process, breaking down carbohydrates into glucose, fats into fatty acids and glycerol, and proteins into amino acids.

Absorption in the small intestine

  • After food is digested, it moves into the blood vessels lining the intestine through a process known as absorption.
  • The inner walls of the small intestine have finger-like projections called villi, which increase the surface area for absorbing digested food.
  • Each villus contains a network of small blood vessels that absorb the digested food materials and transport them via the blood vessels to different body organs for assimilation.
  • Assimilation involves the use of absorbed substances, such as proteins, by different organs of the body to build complex substances.
  • In cells, glucose is broken down into carbon dioxide and water with the help of oxygen, releasing energy.
  • Undigested and unabsorbed food enters the large intestine for further processing.

Large Intestine

  • The large intestine is wider and shorter compared to the small intestine.
  • It is approximately 1.5 meters in length.
  • It absorbs water and certain salts from undigested food material.
  • The remaining waste moves into the rectum, where it stays as semi-solid feces. 
  • Periodically, the fecal matter is eliminated through the anus. This process is known as egestion.

Digestion in Grass-eating Animals

  • Grass-eating animals like cows and buffaloes engage in continuous chewing even when not actively eating.
  • Upon ingestion, grass is quickly swallowed and stored in the rumen, a stomach compartment.
  • In the rumen, food undergoes partial digestion, forming cud, which is later regurgitated in small lumps for re-chewing.
  • This process of re-chewing cud is known as rumination, identifying these animals as ruminants.

Nutrition in Animals Class 7 Notes Science Chapter 2

  • Ruminants, such as cattle and deer, benefit from bacteria in the rumen that aid in cellulose digestion.
  • Cellulose, a carbohydrate abundant in grass, remains indigestible for many animals, including humans.
  • Animals like horses and rabbits feature a large structure called the caecum, aiding in cellulose digestion with specific bacteria.

Question for Chapter Notes: Nutrition in Animals
Try yourself:Why can't humans digest cellulose?
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Diarrhea

  • Sometimes, individuals may experience frequent passing of watery stool, a condition known as diarrhea.
  • Diarrhea can be triggered by factors such as infection, food poisoning, or indigestion and is prevalent in India, especially among children.
  • Severe cases of diarrhea can potentially lead to fatality due to the excessive loss of water and salts from the body.
  • It is crucial not to overlook diarrhea; even before consulting a doctor, the patient should consume ample boiled and cooled water with a pinch of salt and sugar dissolved in it. This solution is referred to as Oral Rehydration Solution (ORS).

Feeding and Digestion in Amoeba

  • Amoeba is a tiny single-celled organism discovered in pond water.
  • Characteristics of Amoeba include a cell membrane, a dense nucleus, and multiple small vacuoles within its cytoplasm.
  • Amoeba is known for its ability to change shape and position frequently.
    Nutrition in Animals Class 7 Notes Science Chapter 2
  • For movement and food capture, Amoeba extends finger-like projections known as pseudopodia or false feet.
  • Amoeba primarily feeds on microscopic organisms, engulfing them by extending pseudopodia around the food particle, forming a food vacuole.
  • Upon trapping the food in a food vacuole, digestive juices are secreted into it, breaking down the food into simpler substances.
  • The digested food is gradually absorbed to be utilized for growth, maintenance, and reproduction.
  • Any undigested remnants are expelled outside the cell through a vacuole.
  • The digestion process in Amoeba involves breaking down food into simpler substances to extract energy, a fundamental process similar across all animals.
  • Subsequently, absorbed nutrients are transported to different body parts through the intestine.
The document Nutrition in Animals Class 7 Notes Science Chapter 2 is a part of the Class 7 Course Science Class 7.
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FAQs on Nutrition in Animals Class 7 Notes Science Chapter 2

1. What are the different ways of taking food?
Ans. The different ways of taking food include ingestion, digestion, absorption, assimilation, and egestion.
2. How does digestion occur in humans?
Ans. In humans, digestion occurs in the mouth, stomach, small intestine, and large intestine, where enzymes break down food into nutrients that can be absorbed by the body.
3. How does digestion occur in grass-eating animals?
Ans. Grass-eating animals have a specialized stomach with multiple chambers that allow for the fermentation of cellulose by bacteria to break down tough plant material.
4. What is the process of feeding and digestion in Amoeba?
Ans. Amoeba feeds by engulfing food particles through phagocytosis, forming a food vacuole where digestion occurs through the action of enzymes. Waste is then expelled through exocytosis.
5. What are the steps involved in the process of digestion in animals?
Ans. The steps involved in the process of digestion in animals include ingestion, digestion, absorption, assimilation, and egestion.
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