Class - 7th Chapter -2: Nutrition and Digestion CBSE /ICSE Board Notes

How Animals Obtain Their Nutrition

⟹The process of breaking down of complex substances of food into simpler substances is called digestion.

Process of Nutrition

➥ Nutrition is the process through which animals obtain and utilize nutrients to sustain their growth, energy, and repair tissues.

1. Ingestion: Taking in food.
2. Digestion: Breaking down food into simpler substances.
3. Absorption: Uptake of nutrients into the body.
4. Assimilation: Utilizing the absorbed nutrients for growth and repair.
5. Egestion: Removing undigested food from the body.

Modes of Procuring Food

➯ Animals have different modes of obtaining their food:-

1. Herbivores: Animals that eat only plants. eg:- Cow.
2. Carnivores: Animals that eat other animals. eg:- Lion.
3. Omnivores: Animals that eat both plants and animals. eg:- Human.
4. Detritivores: Animals that feed on dead organic matter. eg:- Earthworm.

Nutrients in Amoeba

➥ Amoeba is a tiny, single-celled organism that gets its nutrients in these simple steps:

Nutrition in Amoeba

1. Ingestion

➥ Amoeba takes in food by surrounding it with its pseudopodia (false feet) and forming a food vacuole.

2. Digestion

➥ Inside the food vacuole, the food is broken down into smaller, soluble molecules by digestive enzymes.

3. Absorption

➥ The nutrients from the digested food move into the Amoeba’s cytoplasm. This process is called diffusion. The remaining undigested particles are left behind.

4. Assimilation

➥ The absorbed nutrients are used to produce energy needed for the Amoeba’s life processes.

5. Egestion

➥ Undigested food is expelled from the Amoeba by pushing it out through the cell membrane.

Nutrition in Animals

Animals follow these steps for nutrition:

1. Ingestion: Intake of food by mouth.
2. Digestion: Breakdown of food into simpler substances.
3. Digestion Process
1. In Mouth: Food is crushed by teeth, mixed with saliva (salivary juice), and tasted. Saliva starts breaking down starch.
2. In Oesophagus: Food moves through the oesophagus by peristaltic movement. No digestion occurs here.
3. In Stomach: The stomach breaks down food with gastric juice. It contains acid and pepsin to digest proteins.
4. In Small Intestine: The small intestine continues digestion, converting proteins to amino acids, carbs to glucose, and fats to fatty acids and glycerol.
5. In Liver: The liver makes bile juice to neutralize stomach acid and help digest fats.
6. In Pancreas: The pancreas releases pancreatic juice, which contains enzymes to digest proteins and fats.
4. Absorption: Nutrients are absorbed in the small intestine through tiny projections called villi.
5. Assimilation: The body uses absorbed nutrients for energy and to build and repair tissues.
6. Egestion: Waste moves to the large intestine, where water is absorbed. The remaining waste is removed from the body through the anus.

Human Teeth and Their Functions

➥ Teeth are hard, bone-like structures in the upper and lower jaws of most vertebrates.

➥ They help in cutting, breaking, and chewing food.

➯ There are two types of teeth:

• Temporary Teeth (Milk Teeth): These are the first set of teeth that appear in childhood.
• Permanent Teeth: These are the adult teeth that replace the milk teeth as one grows older.

Human teeth play a crucial role in digestion:

• Incisors: Sharp teeth used for cutting food.
• Canines: Pointed teeth used for tearing food.
• Premolars: Flat teeth used for grinding and crushing food.
• Molars: Large, flat teeth used for thorough grinding and crushing.

Digestive System in Ruminants

⟹ Ruminants have a specialized digestive system to process plant material:

• Rumen: The largest stomach chamber where fermentation of plant material occurs.
• Reticulum: Collects smaller particles and moves them to the omasum.
• Omasum: Absorbs water and nutrients from the food.
• Abomasum: The true stomach where enzymatic digestion occurs.