Class 7 Science Nutrition in Animals Notes

Class 7 Science Nutrition in Animals Notes

Introduction:
The chapter “Nutrition in Animals” explores how animals obtain and utilize food to meet their energy needs. Unlike plants, animals cannot make their own food through photosynthesis. Instead, they depend on plants and other animals for nourishment. This chapter explains the process of nutrition in different types of animals, from simple organisms to complex ones, and introduces key concepts like ingestion, digestion, absorption, and assimilation of food.

Key Concepts Covered:

  1. What is Nutrition?
    • Nutrition is the process by which living organisms obtain and utilize food to sustain their life processes, such as growth, reproduction, and energy production.
    • Animals get their food from plants (herbivores), other animals (carnivores), or both (omnivores).
  2. Modes of Nutrition in Animals:
    • Heterotrophic Nutrition: Animals depend on other organisms (plants or other animals) for food. They cannot make their own food.
    • Animals can be divided into three categories based on their food habits:
      • Herbivores: Animals that eat only plants (e.g., cows, deer).
      • Carnivores: Animals that eat only other animals (e.g., lions, tigers).
      • Omnivores: Animals that eat both plants and animals (e.g., humans, bears).
  3. The Digestive System:
    • The digestive system is responsible for breaking down food into simpler forms that can be absorbed and utilized by the body.
    • Ingestion is the intake of food into the mouth.
    • Digestion is the process where food is broken down into smaller components (nutrients).
    • Absorption is the process of absorbing nutrients into the bloodstream.
    • Assimilation is the incorporation of absorbed nutrients into the cells for growth and energy.
    • Egestion is the elimination of undigested food from the body.
  4. Human Digestive System:
    • The human digestive system consists of the following parts:
      • Mouth: Food is ingested and mechanically broken down by teeth.
      • Esophagus: A tube that moves food from the mouth to the stomach.
      • Stomach: Food is mixed with gastric juices and broken down further.
      • Small Intestine: Most digestion and absorption of nutrients occur here.
      • Large Intestine: Absorbs water and forms feces.
      • Anus: The opening through which undigested food (feces) is excreted.
  5. Digestive Enzymes:
    • Enzymes are biological catalysts that speed up the chemical reactions involved in digestion.
    • Examples of digestive enzymes:
      • Amylase: Breaks down starch into sugars (found in saliva and pancreatic juice).
      • Protease: Breaks down proteins into amino acids.
      • Lipase: Breaks down fats into fatty acids and glycerol.
  6. Digestion in Simple Organisms:
    • Amoeba: Ingests food through a process called phagocytosis, where the food is engulfed in a food vacuole and digested by enzymes.
    • Hydra: A simple organism that has a central body cavity where digestion occurs. Food is taken in through the mouth and digested in the cavity.
  7. Ruminants and Their Digestion:
    • Ruminants (e.g., cows, goats) have a specialized stomach with four chambers that allow them to digest plant material efficiently.
    • They chew their food, swallow it into the rumen, where it is partially digested, then regurgitate it for further chewing (called cud chewing) before it is fully digested.

Important Questions with Answers:

  1. What is the role of the digestive system in animals?
    • Answer: The digestive system breaks down food into simpler substances that can be absorbed and used by the body for energy, growth, and repair.
  2. What are the main types of nutrition in animals?
    • Answer: The main types of nutrition in animals are herbivores (plant-eaters), carnivores (meat-eaters), and omnivores (both plant- and meat-eaters).
  3. What is the function of the small intestine in the human digestive system?
    • Answer: The small intestine is responsible for the majority of digestion and the absorption of nutrients into the bloodstream.
  4. What is the difference between digestion in humans and amoeba?
    • Answer: In humans, digestion occurs in a specialized digestive system, while in amoeba, food is engulfed by the cell membrane and digested inside a food vacuole.
  5. Explain the process of digestion in ruminants.
    • Answer: Ruminants have a multi-chambered stomach. They swallow food into the rumen, where it is partially digested, then regurgitate it as cud to chew it again for better digestion before it moves to other stomach chambers.
  6. Why do humans need digestive enzymes?
    • Answer: Digestive enzymes speed up the breakdown of food into smaller, absorbable nutrients like sugars, amino acids, and fatty acids.
  7. What is the function of bile in digestion?
    • Answer: Bile is produced by the liver and stored in the gall bladder. It helps break down fats into smaller droplets, making them easier to digest by lipase.