Nutrition in Animals: Class 7 Notes CBSE Science

Introduction to Nutrition in Animals

Nutrition is fundamental to all living organisms. While plants can synthesize their own food through photosynthesis, animals including humans depend on external sources for nutrients. Understanding nutrition in animals class 7 helps students grasp how different organisms obtain and utilize food for survival, growth, and energy.

This comprehensive guide covers class 7 science notes with detailed explanations, visual aids, and practice questions aligned with the CBSE curriculum.

What is Nutrition?

Nutrition is the process by which organisms obtain food and utilize it for energy, growth, and maintenance of body functions. Food contains essential nutrients chemical substances that provide:

• Energy for daily activities
• Building materials for growth and repair
• Regulatory substances for metabolic processes

Essential Nutrients

The primary nutrients required by animals include:

1. Carbohydrates - Primary energy source
2. Proteins - Building blocks for body tissues
3. Fats - Energy storage and insulation
4. Vitamins - Regulate body functions
5. Minerals - Support various physiological processes

Modes of Nutrition

Living organisms exhibit two main modes of nutrition:

1. Autotrophic Nutrition

• Organisms prepare their own food (e.g., green plants)
• Use chlorophyll and sunlight for photosynthesis
• Also called autotrophs or producers

2. Heterotrophic Nutrition

• Organisms obtain food from other sources
• Cannot manufacture their own food
• All animals are heterotrophs or consumers
• Some plants (insectivorous plants like Pitcher plant, Venus flytrap) also exhibit heterotrophic characteristics

Classification of Animals Based on Food Habits

Animals are categorized into three groups based on their dietary preferences:

Herbivores (Plant Eaters)

Animals that feed exclusively on plants and plant products.

Examples: Cow, buffalo, deer, sheep, goat, rabbit, elephant

Characteristics:

• Flat grinding teeth (molars) for chewing plant material
• Long digestive system for breaking down cellulose
• Some have specialized stomachs (ruminants)

Carnivores (Meat Eaters)

Animals that feed on other animals.

Examples: Tiger, lion, wolf, leopard, eagle

Characteristics:

• Sharp pointed teeth (canines) for tearing flesh
• Strong claws for hunting
• Shorter digestive tract compared to herbivores

Omnivores (Plant and Meat Eaters)

Animals that consume both plant and animal matter.

Examples: Humans, bears, crows, cockroaches, rats

Characteristics:

• Combination of different types of teeth
• Can digest both plant and animal matter
• Flexible dietary habits

Difference Between Autotrophic and Heterotrophic Nutrition

Aspect	Autotrophic Nutrition	Heterotrophic Nutrition
Occurrence	Only in green plants	In all non-green plants and animals
Raw Materials	Carbon dioxide and water	Obtain food from autotrophs (directly or indirectly)
Chlorophyll	Essential for food synthesis	Absent
Sunlight	Required for photosynthesis	Not needed
Dependency	Independent (self-sufficient)	Dependent on other organisms

Types of Heterotrophic Nutrition in Animals

1. Holozoic Nutrition

The most common type of nutrition in animals where solid food is ingested and then digested internally.

Process Steps:

1. Ingestion - Taking in food
2. Digestion - Breaking down complex food into simpler forms
3. Absorption - Uptake of digested nutrients
4. Assimilation - Utilization of absorbed nutrients by body cells
5. Egestion - Removal of undigested waste

Examples: Humans, dogs, cats, birds

2. Parasitic Nutrition

Organisms obtain nutrients from the body of another living organism (host) without killing it.

Examples:

• Tapeworm - Lives in human intestine
• Roundworm - Intestinal parasite
• Leeches - External parasites that suck blood
• Lice - Feed on blood and skin

3. Saprophytic/Saprotrophic Nutrition

Organisms obtain nutrients from dead and decaying organic matter.

Examples:

• Fungi
• Certain bacteria
• Decomposers in ecosystem

Human Digestive System: Structure and Function

The human digestive system is approximately 8-10 meters long and consists of the alimentary canal and associated digestive glands.

Components of the Digestive System

A. Alimentary Canal

1. Mouth (Buccal Cavity)

• Entry point for food
• Contains teeth for mechanical digestion
• Tongue for taste and mixing food with saliva
• Salivary glands secrete saliva (1.0-1.5 liters daily)

2. Teeth

Types of Teeth (32 in adults):

• Incisors (8) - Chisel-shaped, for cutting food
• Canines (4) - Pointed, for tearing food
• Premolars (8) - For grinding food
• Molars (12) - Flat surfaces for grinding and crushing

Tooth Structure:

• Enamel - Hardest substance in body, outer protective layer
• Dentine - Bone-like layer beneath enamel
• Pulp Cavity - Contains blood vessels and nerves
• Gums - Soft tissue holding teeth in place

Dental Formula for Adults: 2123/2123 (each half of jaw)

Milk Teeth vs Permanent Teeth:

• Milk Teeth: 20 teeth, appear from 6 months, no molars
• Permanent Teeth: 28-32 teeth, replace milk teeth at 6-8 years
• Wisdom Teeth: 4 molars appear after 18 years

3. Oesophagus (Food Pipe)

• Muscular tube connecting mouth to stomach
• Length: 25 cm approximately
• Performs peristaltic movements (wave-like contractions)
• Does not digest food, only transports it
• Epiglottis prevents food from entering windpipe

4. Stomach

• J-shaped muscular bag
• Stores food for 4-5 hours
• Inner walls have gastric glands

Functions:

• Secretes gastric juice (HCl, pepsin, mucus)
• Churns food into semi-solid paste called chyme
• Kills bacteria with hydrochloric acid
• Initiates protein digestion

5. Small Intestine

• Longest part of alimentary canal (6-7 meters)
• Highly coiled structure
• Three parts: Duodenum, Jejunum, Ileum

Key Features:

• Villi - Finger-like projections on inner wall
• Increase surface area for absorption
• Richly supplied with blood vessels
• Complete digestion and maximum absorption occurs here

6. Large Intestine

• Wider but shorter than small intestine (1.5 meters)
• Absorbs water and minerals
• Forms solid waste (faeces)
• Ends at rectum and anus

7. Rectum and Anus

• Rectum - Stores faeces temporarily
• Anus - Opening for egestion of waste

B. Digestive Glands

1. Salivary Glands

• Secrete saliva containing enzyme salivary amylase (ptyalin)
• Breaks down starch into maltose (sugar)
• Moistens food for easy swallowing
• Three pairs: Parotid, Submandibular, Sublingual

2. Liver

• Largest gland in the human body (1.5 kg)
• Produces bile juice stored in gall bladder
• Bile emulsifies fats (breaks large fat droplets into smaller ones)
• No digestive enzymes in bile
• Removes toxins from blood

3. Pancreas

• Located below the stomach
• Secretes pancreatic juice into duodenum
• Contains multiple enzymes:
  • Trypsin - Digests proteins
  • Amylase - Digests carbohydrates
  • Lipase - Digests fats

4. Intestinal Glands

• Present in the wall of small intestine
• Secrete intestinal juice (complete digestion)

Process of Digestion in Humans

Step-by-Step Breakdown

1. Mouth (Buccal Cavity)

• Mechanical Digestion: Teeth cut, tear, and grind food
• Chemical Digestion: Salivary amylase breaks starch → maltose
• Duration: Food stays for few seconds
• Formation of bolus (food ball)

2. Oesophagus

• Peristalsis pushes food to stomach
• No digestion occurs
• Takes 5-10 seconds

3. Stomach

• Mechanical action: Churning mixes food with gastric juice
• Chemical digestion:
  • HCl activates pepsinogen → pepsin
  • Pepsin breaks proteins → peptones
  • Kills harmful bacteria
• Forms chyme (acidic semi-liquid food)
• Duration: 4-5 hours

4. Small Intestine

• Duodenum receives:
  • Bile from liver (emulsifies fats)
  • Pancreatic juice (digests all nutrients)
  • Intestinal juice (completes digestion)

Complete Digestion:

• Carbohydrates → Glucose
• Proteins → Amino acids
• Fats → Fatty acids and glycerol

5. Absorption

• Occurs through villi in small intestine
• Glucose and amino acids → blood vessels
• Fatty acids and glycerol → lymphatic vessels
• Transported to all body cells

6. Large Intestine

• Absorbs water and minerals
• Undigested food forms faeces
• Bacterial action on residue

7. Egestion

• Removal of faeces through anus
• Completes digestive process

Formulas and Equations in Digestion

Process	Equation/Formula	Explanation
Starch Digestion (Mouth)	Starch + Salivary Amylase → Maltose	Initial breakdown of carbohydrates
Protein Digestion (Stomach)	Protein + Pepsin (HCl) → Peptones	Partial protein breakdown
Complete Carbohydrate Digestion	Maltose + Maltase → Glucose	Final breakdown into simple sugar
Complete Protein Digestion	Peptones + Trypsin → Amino acids	Final protein breakdown
Fat Emulsification	Large fat droplets + Bile → Small fat droplets	Physical breakdown of fats
Fat Digestion	Fats + Lipase → Fatty acids + Glycerol	Chemical breakdown of fats
Cellulose Digestion (Ruminants)	Cellulose + Cellulase (bacteria) → Glucose	Only in ruminants with bacterial help

Digestion in Grass-Eating Animals (Ruminants)

What are Ruminants?

Animals that swallow grass quickly and store it in a specialized stomach compartment, then bring it back to mouth for thorough chewing.

Examples: Cow, buffalo, goat, sheep, deer, giraffe

Ruminant Stomach Structure

Ruminants have a four-chambered stomach:

1. Rumen (Largest chamber)
   • Stores swallowed grass
   • Bacterial action starts cellulose breakdown
   • Partial digestion occurs
2. Reticulum (Honeycomb-like structure)
   • Forms balls of partially digested food called cud
   • Sends cud back to mouth for chewing
3. Omasum (Many-layered structure)
   • Absorbs water and minerals
   • Further grinds food
4. Abomasum (True stomach)
   • Similar to human stomach
   • Secretes digestive juices
   • Completes protein digestion

Process of Rumination

1. Quick swallowing of grass without chewing
2. Storage in rumen
3. Bacterial fermentation breaks cellulose partially
4. Cud formation in reticulum
5. Regurgitation - Bringing cud back to mouth
6. Thorough chewing (rumination)
7. Re-swallowing to omasum and abomasum
8. Complete digestion and absorption

Importance: Allows grazing animals to quickly consume large amounts of food and digest cellulose (which humans cannot digest) with bacterial help.

Nutrition in Amoeba (Unicellular Organism)

Amoeba is a microscopic single-celled organism that exhibits holozoic nutrition.

Structure

• Cell membrane - Controls entry and exit
• Cytoplasm - Contains cell organelles
• Nucleus - Controls cell activities
• Pseudopodia (False feet) - For movement and food capture
• Food vacuole - Temporary digestive chamber
• Contractile vacuole - Expels excess water

Process of Nutrition in Amoeba

1. Ingestion

• Amoeba senses food (bacteria, algae)
• Extends pseudopodia around food particle
• Engulfs food forming food vacuole
• Process called phagocytosis

2. Digestion

• Digestive enzymes released into food vacuole
• Complex food broken into simpler molecules
• Takes several hours

3. Absorption

• Digested nutrients diffuse into cytoplasm
• Used for energy and growth

4. Assimilation

• Nutrients utilized for metabolic activities
• Energy production through cellular respiration

5. Egestion

• Undigested waste accumulates in food vacuole
• Vacuole moves to cell surface
• Waste expelled by rupturing cell membrane at any point
• No specific opening for egestion

Time Duration: Entire process takes 1-2 hours

Nutrition in Starfish

Starfish exhibits unique feeding mechanism:

• Feeds on animals with hard calcium carbonate shells (mollusks)
• Opens the shell using tube feet
• Everts its stomach through its mouth
• Stomach wraps around soft tissue inside shell
• Digests food externally
• Retracts stomach back into body
• Completes digestion internally

Important Definitions for Class 7 Nutrition in Animals

Term	Definition
Nutrition	Process of obtaining and utilizing food for growth and energy
Ingestion	Taking in food through mouth
Digestion	Breaking down complex food into simpler absorbable forms
Absorption	Uptake of digested nutrients into blood
Assimilation	Utilization of absorbed nutrients by body cells
Egestion	Removal of undigested waste from body
Peristalsis	Wave-like muscular contractions that move food through alimentary canal
Villi	Finger-like projections in small intestine for absorption
Chyme	Semi-solid acidic food formed in stomach
Bolus	Ball of chewed food formed in mouth
Cud	Partially digested food returned to mouth for re-chewing in ruminants
Rumination	Process of chewing cud in ruminants
Enamel	Hardest substance in body, outer layer of tooth
Pseudopodia	Temporary finger-like projections in Amoeba for movement and feeding
Phagocytosis	Process of engulfing food particles (in Amoeba)

Common Health Issues Related to Nutrition and Digestion

1. Tooth Decay

Cause:

• Poor oral hygiene
• Formation of plaque (sticky film of bacteria, food particles, and saliva)
• Bacteria produce acid that damages enamel

Prevention:

• Brush twice daily
• Rinse after meals
• Avoid excessive sugary foods
• Regular dental check-ups

2. Diarrhoea

Definition: Frequent passage of watery stool

Causes:

• Infection
• Food poisoning
• Indigestion
• Contaminated water

Treatment:

• Oral Rehydration Solution (ORS)
• Mixture of boiled water, salt, and sugar
• Prevents dehydration
• Consult doctor if severe

Prevention:

• Drink clean water
• Wash hands before eating
• Eat fresh, properly cooked food

3. Constipation

Cause:

• Low fiber diet
• Insufficient water intake
• Lack of exercise

Prevention:

• Eat fiber-rich foods (fruits, vegetables, whole grains)
• Drink adequate water
• Regular exercise

4. Acidity

Cause:

• Excess acid production in stomach
• Irregular eating habits
• Spicy foods

Symptoms:

• Burning sensation in chest
• Sour taste in mouth

Prevention:

• Regular meal timings
• Avoid oily and spicy foods
• Don't skip meals

Nutrition in Animals Class 7 Extra Questions with Answers

Short Answer Questions (2-3 Marks)

Q1. What are different types of teeth in our mouth?

Answer: Human adults have 32 teeth of four types:

• Incisors (8): Front teeth for cutting and biting food
• Canines (4): Pointed teeth for tearing food
• Premolars (8): For crushing and grinding food
• Molars (12): Back teeth with flat surfaces for thorough grinding

Q2. Why is digestion essential?

Answer: Digestion is essential because:

• Food we eat is complex and cannot be directly absorbed by body
• Digestive process breaks down complex molecules into simpler, soluble forms
• Only simple molecules can pass through intestinal walls into blood
• These nutrients provide energy and materials for growth, repair, and maintenance

Q3. What happens during chemical digestion of food in the mouth?

Answer: In the mouth:

• Salivary glands secrete saliva containing enzyme salivary amylase
• Salivary amylase acts on starch and converts it into maltose (sugar)
• This is the first step of chemical digestion
• Saliva also moistens food for easy swallowing

Q4. What are the various steps involved in holozoic mode of nutrition?

Answer: The five steps of holozoic nutrition are:

1. Ingestion: Taking in food through mouth
2. Digestion: Breaking down complex food into simpler forms
3. Absorption: Taking up digested nutrients into blood
4. Assimilation: Utilization of absorbed nutrients by cells for energy
5. Egestion: Removal of undigested waste from body

Q5. What is tooth decay?

Answer: Tooth decay is the destruction of tooth enamel. When we don't clean teeth after eating, food particles mix with bacteria and saliva to form a sticky substance called plaque. Bacteria in plaque produce acids that gradually dissolve the hard enamel, creating cavities. This causes pain, sensitivity, and tooth damage if untreated.

Q6. What is the function of the tongue during digestion?

Answer: The tongue performs several important functions:

• Helps in mixing food with saliva
• Assists in chewing by moving food between teeth
• Contains taste buds for tasting food
• Helps in rolling food into a bolus
• Pushes food backward for swallowing
• Prevents food from entering windpipe during swallowing

Q7. What happens to starch, proteins, and fats during digestion?

Answer:

• Starch (Carbohydrates):
  • Mouth: Starch → Maltose (by salivary amylase)
  • Small intestine: Maltose → Glucose (by maltase)
• Proteins:
  • Stomach: Proteins → Peptones (by pepsin)
  • Small intestine: Peptones → Amino acids (by trypsin)
• Fats:
  • Small intestine: Bile emulsifies fats
  • Fats → Fatty acids + Glycerol (by lipase)

Q8. Why is it necessary to maintain oral hygiene?

Answer: Maintaining oral hygiene is necessary because:

• Prevents tooth decay and cavities
• Stops formation of plaque and tartar
• Prevents gum diseases
• Eliminates bad breath
• Protects enamel from bacterial acids
• Ensures healthy teeth throughout life
• Proper brushing and rinsing removes food particles that attract bacteria

Long Answer Questions (5 Marks)

Q9. Explain the structure of a tooth.

Answer: A tooth has the following parts:

External Structure:

• Crown: Visible part above gums, covered with enamel
• Root: Part embedded in jaw bone, holds tooth firmly
• Neck: Junction between crown and root

Internal Structure:

• Enamel: Hardest substance in body, white outer covering, protects tooth
• Dentine: Bone-like material beneath enamel, yellow in color, forms bulk of tooth
• Pulp Cavity: Central chamber containing:
  • Blood vessels (provide nutrients)
  • Nerves (provide sensation)
  • Soft connective tissue
• Gums: Soft pink tissue surrounding tooth, holds it in jaw socket
• Cement: Covers root surface, helps anchor tooth to jaw bone

Q10. What is the largest gland of the body? Explain its function.

Answer: The liver is the largest gland in the human body, weighing about 1.5 kg.

Functions of Liver:

1. Produces Bile:
   • Bile is a greenish-yellow digestive juice
   • Stored in gall bladder
   • Helps in emulsification of fats
   • Makes fats easier to digest
2. Detoxification:
   • Removes toxic substances from blood
   • Converts harmful ammonia to less harmful urea
3. Storage:
   • Stores glucose as glycogen
   • Stores vitamins and minerals
   • Releases glucose when body needs energy
4. Protein Synthesis:
   • Produces blood proteins
   • Produces clotting factors
5. Metabolic Functions:
   • Regulates blood sugar levels
   • Processes nutrients absorbed from intestines

Q11. What is the role of the large intestine in the human body?

Answer: The large intestine plays several important roles:

Structure:

• Wider but shorter than small intestine (about 1.5 meters)
• Extends from small intestine to rectum

Functions:

1. Water Absorption:
   • Absorbs excess water from undigested food
   • Prevents dehydration
   • Concentrates waste material
2. Mineral Absorption:
   • Absorbs remaining minerals and salts
   • Particularly sodium and chloride
3. Formation of Faeces:
   • Converts liquid waste into solid form
   • Stores faeces temporarily
4. Bacterial Action:
   • Contains beneficial bacteria
   • Bacteria synthesize vitamin K and some B vitamins
   • Help in final breakdown of residue
5. Egestion:
   • Pushes faeces to rectum
   • Eliminates waste through anus

Q12. How does nutrition in Amoeba take place?

Answer: Amoeba exhibits holozoic nutrition through the following steps:

1. Ingestion:

• Amoeba comes in contact with food (bacteria, algae)
• Forms pseudopodia (false feet) around food
• Pseudopodia fuse, engulfing food particle
• Forms food vacuole containing trapped food
• Process called phagocytosis

2. Digestion:

• Food vacuole moves through cytoplasm
• Digestive enzymes secreted into vacuole
• Complex food broken into simpler molecules
• Similar to intracellular digestion

3. Absorption:

• Digested nutrients diffuse out of food vacuole
• Pass into surrounding cytoplasm
• Distributed throughout cell

4. Assimilation:

• Nutrients used for:
  • Energy production
  • Growth
  • Repair
  • Reproduction

5. Egestion:

• Undigested waste remains in vacuole
• Vacuole moves toward cell membrane
• Membrane ruptures at any point
• Waste expelled out (no fixed point)

Time: Entire process takes 1-2 hours

Q13. What is the function of villi and where are they located?

Answer:

Location: Villi are finger-like projections present on the inner walls of the small intestine.

Structure:

• Microscopic projections (1-1.5 mm height)
• Millions of villi line the intestinal wall
• Covered with thin epithelial layer
• Rich network of blood capillaries inside
• Each villus contains a lymphatic vessel (lacteal)

Functions:

1. Increase Surface Area:
   • Provide enormous surface area for absorption
   • Small intestine length: 6-7 meters
   • Villi multiply surface area by 30-40 times
   • Enables maximum nutrient absorption
2. Absorption of Nutrients:
   • Glucose and amino acids: Absorbed into blood capillaries
   • Fatty acids and glycerol: Absorbed into lacteals (lymphatic vessels)
   • Quick absorption due to thin walls
   • Single cell layer separates nutrients from blood
3. Transportation:
   • Blood vessels carry nutrients to liver via hepatic portal vein
   • Lacteals carry fats to lymphatic system
   • Eventually nutrients reach all body cells

Importance: Without villi, absorption would be inefficient and body would not get adequate nutrition.

Q14. What is the fate of absorbed carbohydrates, proteins, and fats?

Answer:

Carbohydrates (Glucose):

• Absorbed as glucose into blood capillaries of villi
• Transported to liver via hepatic portal vein
• Liver regulates blood glucose level
• Excess glucose stored as glycogen in liver and muscles
• Released when body needs energy
• Used by cells for energy production through cellular respiration

Proteins (Amino Acids):

• Absorbed as amino acids into blood capillaries
• Transported to liver
• Distributed to all body cells through bloodstream
• Used for:
  • Building new proteins for growth
  • Repairing damaged tissues
  • Making enzymes and hormones
  • Replacing worn-out cells
• Excess amino acids broken down by liver
• Nitrogen converted to urea (excreted by kidneys)

Fats (Fatty Acids and Glycerol):

• Absorbed into lacteals (lymphatic vessels) in villi
• Enter bloodstream through lymphatic system
• Transported to tissues
• Used for:
  • Energy storage (most concentrated energy source)
  • Building cell membranes
  • Protecting organs
  • Insulation
• Excess stored as adipose (fat) tissue under skin

Q15. Does the food pipe help in digestion?

Answer: No, the food pipe (oesophagus) does not help in digestion directly.

Functions of Food Pipe:

1. Transportation Only:
   • Acts as passage between mouth and stomach
   • Length approximately 25 cm
   • Muscular tube with no digestive glands
2. Peristaltic Movement:
   • Performs wave-like muscular contractions
   • Pushes food downward toward stomach
   • Works against gravity
   • Takes 5-10 seconds for food to reach stomach
3. Protection:
   • Epiglottis (flap) covers windpipe during swallowing
   • Prevents food from entering respiratory tract
   • Causes choking if malfunctions

Note: All digestion occurs in mouth, stomach, and intestines. The oesophagus only transports food without any chemical or mechanical digestion.

Q16. What is the role of the pancreas in digestion?

Answer: The pancreas is a crucial digestive gland with multiple functions:

Location: Below the stomach, in the abdomen

Structure:

• Both exocrine (produces digestive enzymes) and endocrine gland (produces hormones)

Digestive Functions:

1. Secretion of Pancreatic Juice:
   • Flows into duodenum (first part of small intestine)
   • Contains multiple digestive enzymes
   • Alkaline in nature (neutralizes acidic chyme from stomach)
2. Enzyme Production:a) Trypsin:
   • Digests proteins
   • Converts peptones into amino acids
   • Works in alkaline medium
   b) Pancreatic Amylase:
   • Digests carbohydrates
   • Converts starch into maltose
   • Completes carbohydrate digestion
   c) Lipase:
   • Digests fats
   • Breaks down fats into fatty acids and glycerol
   • Works on emulsified fats
3. pH Regulation:
   • Secretes bicarbonate ions
   • Neutralizes stomach acid
   • Creates optimal pH for intestinal enzymes

Hormonal Functions:

• Produces insulin (regulates blood sugar)
• Produces glucagon (raises blood sugar)

Importance: Without pancreatic enzymes, proper digestion of all three major nutrients would be impossible.

Q17. What important role does the small intestine play in the absorption of digested food?

Answer: The small intestine is the primary site of absorption with several specialized features:

Structure:

• Longest part of digestive system (6-7 meters)
• Highly coiled to fit in abdominal cavity
• Three parts: Duodenum, Jejunum, Ileum

Features for Efficient Absorption:

1. Large Surface Area:
   • Inner wall folded into millions of villi
   • Each villus has microvilli
   • Total surface area: 200-300 square meters
   • Provides maximum area for nutrient absorption
2. Rich Blood Supply:
   • Dense network of blood capillaries in each villus
   • Quick transport of absorbed nutrients
   • Glucose and amino acids enter bloodstream
3. Thin Walls:
   • Single layer of epithelial cells
   • Easy diffusion of nutrients
   • Quick absorption into blood
4. Presence of Lacteals:
   • Lymphatic vessels in each villus
   • Absorb fatty acids and glycerol
   • Transport fats to lymphatic system
5. Slow Movement of Food:
   • Food stays 3-5 hours
   • Allows complete absorption
   • Peristalsis ensures mixing
6. Intestinal Juice:
   • Completes final digestion
   • Contains enzymes for all nutrients

Process:

• Nutrients diffuse through intestinal walls
• Enter blood or lymph
• Transported to liver
• Distributed to all body cells

Importance: About 90% of nutrient absorption occurs in the small intestine, making it essential for nutrition.

Q18. What are omasum and abomasum and where are they located?

Answer: Omasum and abomasum are two of the four chambers in a ruminant's stomach.

Location: In grass-eating animals like cows, buffaloes, sheep, and goats

Four Stomach Chambers (in sequence):

1. Rumen (largest)
2. Reticulum
3. Omasum (third chamber)
4. Abomasum (fourth chamber)

Omasum:

• Structure:
  • Also called "many-plies"
  • Has many folds or layers like pages of a book
  • Muscular chamber
• Functions:
  • Absorbs water and minerals from partially digested food
  • Further grinds food mechanically
  • Squeezes out excess water
  • Prepares food for final digestion

Abomasum:

• Structure:
  • True or real stomach
  • Similar to human stomach
  • Secretory chamber with gastric glands
• Functions:
  • Secretes hydrochloric acid (HCl)
  • Produces enzyme pepsin
  • Digests proteins into peptones
  • Functions like a normal stomach
  • Final stage before food enters intestine

Process Flow: Rumen → Reticulum → Cud chewing → Omasum → Abomasum → Small Intestine

Importance: This specialized four-chamber system allows ruminants to digest cellulose with the help of bacteria, which non-ruminants cannot digest.

Multiple Choice Questions (MCQs) for Practice

Q1. In which of the following organs will the digestion of starch take place?

• (a) Mouth 
• (b) Stomach
• (c) Small intestine
• (d) Large intestine

Answer: (a) Mouth
Explanation: Starch digestion begins in the mouth where salivary amylase breaks it down into maltose.

Q2. Which option shows the correct order?

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

• (a) 1-2-3-4-5
• (b) 2-5-3-4-1
• (c) 2-4-5-3-1
• (d) 2-5-4-3-1 

Answer: (d) 2-5-4-3-1
Explanation: Correct sequence is Ingestion → Digestion → Absorption → Assimilation → Egestion

Q3. The process of taking in food is also called:

• (a) Ingestion 
• (b) Egestion
• (c) Digestion
• (d) Absorption

Answer: (a) Ingestion

Q4. Pseudopodia help in the ingestion of food in:

• (a) Amoeba 
• (b) Cockroach
• (c) Hydra
• (d) Birds

Answer: (a) Amoeba
Explanation: Amoeba uses pseudopodia (false feet) to engulf food particles.

Q5. Digestion of food inside food vacuole occurs in:

• (a) Hydra
• (b) Cockroach
• (c) Amoeba 
• (d) Birds

Answer: (c) Amoeba

Q6. Hydrochloric acid in stomach:

• (a) Helps in digestion of fat
• (b) Kills bacteria ingested with food 
• (c) Converts starch into sugars
• (d) Helps in the digestion of protein

Answer: (b) Kills bacteria ingested with food
Explanation: HCl creates acidic environment that kills harmful bacteria, also activates pepsinogen to pepsin.

Q7. During what age are milk teeth replaced by permanent teeth?

• (a) 6 to 8 years 
• (b) 8-12 years
• (c) 2-4 years
• (d) 4-7 years

Answer: (a) 6 to 8 years

Q8. Stomach 3 in ruminants is also called:

• (a) Omasum 
• (b) Rumen
• (c) Abomasum
• (d) Reticulum

Answer: (a) Omasum
Explanation: Third chamber is omasum, fourth is abomasum (true stomach).

Q9. Which is the largest gland in the human body?

• (a) Pancreas
• (b) Stomach
• (c) Liver 
• (d) Large intestine

Answer: (c) Liver

Q10. Which process involves the utilization of absorbed nutrients by body cells for energy production?

• (a) Digestion
• (b) Ingestion
• (c) Assimilation
• (d) Absorption

Answer: (c) Assimilation

Additional Practice Questions

Q11. The finger-like projections in the small intestine are called:

• (a) Villi 
• (b) Cilia
• (c) Microvilli
• (d) Pseudopodia

Q12. Which enzyme is present in saliva?

• (a) Pepsin
• (b) Trypsin
• (c) Salivary amylase 
• (d) Lipase

Q13. The food pipe is also known as:

• (a) Trachea
• (b) Oesophagus 
• (c) Pharynx
• (d) Larynx

Q14. Bile is stored in:

• (a) Liver
• (b) Pancreas
• (c) Gall bladder 
• (d) Stomach

Q15. The process of bringing back swallowed food to mouth for chewing in ruminants is called:

• (a) Egestion
• (b) Rumination 
• (c) Ingestion
• (d) Peristalsis

Study Tips for Class 7 Nutrition in Animals

For Better Understanding:

1. Draw Diagrams: Sketch digestive system, tooth structure, and ruminant stomach
2. Make Flow Charts: Create process flow for digestion steps
3. Use Mnemonics: Remember tooth types - "I Can't Prevent Many" (Incisors, Canines, Premolars, Molars)
4. Create Comparison Tables: Compare autotrophic vs heterotrophic, herbivores vs carnivores
5. Watch Educational Videos: Visual learning helps understand complex processes

For Exam Preparation:

1. Focus on definitions and technical terms
2. Practice diagram labeling
3. Understand the sequence of digestive processes
4. Solve NCERT questions thoroughly
5. Learn differences between related concepts
6. Memorize formulas and equations
7. Practice MCQs and previous year questions

Important Topics for Revision:

• Types of nutrition and feeding habits
• Human digestive system parts and functions
• Step-by-step digestion process
• Ruminant digestion
• Nutrition in Amoeba
• Role of digestive glands
• Structure and function of villi
• Health issues related to digestion

Conclusion

Understanding nutrition in animals class 7 provides foundational knowledge about how living organisms obtain and process food. This chapter covers essential concepts including modes of nutrition, types of digestive systems, the human alimentary canal, and specialized feeding mechanisms in different animals.

Important from class 7 science chapter 2 nutrition in animals:

• All animals are heterotrophs and depend on external food sources
• The human digestive system is a complex tube with specialized organs
• Different animals have evolved unique digestive systems suited to their diet
• Proper nutrition and digestive health are essential for overall wellbeing
• Understanding these processes helps us make better dietary choices

Regular revision using these nutrition in animals class 7 notes along with consistent practice of nutrition in animals class 7 extra questions with answers will ensure excellent performance in examinations and build a strong foundation for higher classes.