Nutrition in Animals Class 7 Science Notes - Chapter 2

we provide short notes class 7 chapter 2 Nutrition also have pdf download link at end.  

Different Ways of Taking Food

The mode of taking food into the body varies in different organisms/spices. Hummingbirds and bees consume plant nectar.Animals that live in water filter nearby small food particles and eat them.

Digestion in Humans

Digestion is the process by which food is broken down into smaller molecules and absorbed by the body.The digestive system involves the coordination of many organs, including the mouth, oesophagus, stomach, small intestine, large intestine, liver, pancreas, and gallbladder, to break down food and absorb nutrients into the body.

Digestion in Humans

Process of Digestion in Humans

Buccal Cavity

The digestive process starts in the buccal cavity which is also known as Mouth.
where food is mechanically and chemically broken down by chewing and mixing with saliva. 
It consists of the tongue and teeth.
Teeth: Aids in the chewing and breaking down of food into smaller particles.
Tongue: is a fleshy, movable organ that is affixed to the buccal cavity's floor at the back.

Saliva and Salivary glands

Saliva is a clear, slightly alkaline fluid produced by the salivary glands in the mouth
It helps to moisten and lubricate food, making it easier to chew and swallow.
Saliva contains enzymes that begin the process of breaking down carbohydrates, making it easier for the digestive system to process the food.
Saliva contains enzymes that begin the process of breaking down carbohydrates, making it easier for the digestive system to process the food.

Tongue 

It is a fleshy muscular organ attached to the back of the buccal cavity's base.
It aids in swallowing by mixing saliva with food while chewing.
Taste buds on the tongue help us recognize different flavours.

Tongue

Oesophagus or food pipe

The swallowed food passes into the food pipe or oesophagus.
It is a 25-cm-long muscular tube with a sphincter (valve/opening) at each end.
Its job is to move food and liquid from the mouth to the stomach after they have been swallowed.
As there is movement through the walls of the food pipe, food is pushed downward.

Stomach

It is a bag-like structure with thick walls.
It takes food from the food pipe and travels through the small intestine to the other opening
The stomach lining produces mucus, hydrochloric acid (HCl), and other digestive juices.
The food is mixed with gastric juices and broken down into smaller particles through muscular contractions.
This mixture, called chyme, then moves into the small intestine, where most of the nutrients are absorbed into the bloodstream.

Small Intestine

This 7.5-meter-long organ is tightly wound.
It gets secretions from the pancreas and liver.
The small intestine is where food is fully digested and absorbed.
Villi are finger-like outgrowths on the interior of the intestine walls.
The surface area for food absorption is increased by villi.
A small network of blood vessels runs through each villus.
Villi absorb food and transport it to the body via blood vessels.
The remaining waste products move into the large intestine, where water and electrolytes are absorbed and the waste is compacted into faeces.

Large Intestine

It is both longer and wider than the small intestine.
It measures 1.5m in length.
Water and salt are absorbed from undigested food in the large intestine.
The rectum is used to expel any remaining waste.
Faecal matter is removed from time to time via the anus (egestion).

Anus

The anus is the opening at the end of the digestive tract through which faeces, or solid waste, are eliminated from the body
The anus is located at the bottom of the large intestine, near the rectum.

Gallbladder

The gallbladder is a small, pear-shaped organ located just below the liver in the upper right side of the abdomen
Its main function is to store and release bile, a digestive fluid produced by the liver.
Bile helps to digest fats and absorb fat-soluble vitamins (such as vitamins A, D, E, and K) in the small intestine
When we eat, bile is released from the gallbladder into the small intestine, where it emulsifies, or breaks down, the fats into small droplets that can be more easily digested and absorbed by the body.

Absorption & Assimilation in Small Intestine

The blood vessels lining the walls of the small intestine absorb the food that has been digested. Absorption is the term used to describe this phenomenon. 
Villi are numerous finger-like protrusions that line the interior of the small intestine walls.
Through blood vessels, the substances that are absorbed are delivered to various organs of the body where they are used to construct complex substances like proteins that are necessary for the body. We refer to this as assimilation.

Digestion in Grass Eating Animals

Animals that consume grass have a different digestive system from people
Even when they are not eating, these animals are constantly chewing.
They quickly swallow the grass and store it in a room called the Rumen.
Cud is the term for the food that has been partially digested by bacteria in the rumen.
Later, the animal puts the cud back in its mouth and slowly chews it once more.
Rumination is the term used to describe this phenomenon and ruminants are the animals that exhibit it.
Additionally, they have very long small intestines, which aid in fully digesting cellulose, the primary ingredient in grass.

Rumination 

Rumination is the process by which the cattle regurgitates previously consumed feed and masticates it a second time.

Feeding and Digestion in Amoeba

Amoeba is a microscopic single-celled organism found in pond water.
Amoeba constantly changes shape and position.

Process of Digestion in Amoeba

Pseudopodia help the amoeba to capture the food particles. Phagocytosis is the name of the process.
Thus, a food vacuole is formed, containing the food substance.
When food passes through the cytoplasm and into the food vacuole, digestive juices are produced.
The food is affected by them and broken down into simpler substances, after which the digested food is absorbed.
Undigested food is finally released into the surrounding water as the food vacuole opens to the exterior

Important Key