2. Nutrition in Animals

Starfish

1. It eats animals that are covered by hard shells of calcium carbonate.
2. After opening the shell, the starfish pops out its stomach through its mouth.
3. It eats the soft animal inside the shell.
4. The stomach then goes back into the body and the food is slowly digested.

Amoeba 

1. It is a microscopic single celled organism. 
2. It has a cell membrane, a rounded nucleus & many small food vacuoles in its cytoplasm.
3. It has finger-like temproary projections of cell membrane called pseudopodia or false feet.
4. It uses pseudopodia to move, capture of food or change its shape & position.

Digestion:

1. Amoeba feeds on some microscopic organisms.
2. When the amoeba senses food, it pushes out one or more pseudopodia around the food to capture it.
3.  The food becomes trapped in a food vacuole where digestive juices are secreted.
4. They act on the food & break it down into simpler substances that can be abosorbed.
5. The absorbed substances are used for growth, maintenance & multiplication.
6. The undigested residue of the food is expelled outside by the vacuole.

Diagram:

Rumination:

All grass eating animals are called ruminants.

Ingestion:

1. The ruminats continuously swallow grass without chewing it much.
2. This partly chewed food is swallowed through the esophagus to the first chamber of the stomach.
3. The stomach of the ruminants has four chambers.

Rumen:

1. It is the first & largest chamber of the stomach.
2. It receives the food swallowed through the esophagus.
3. The food is stored here & broken down.
4. The partly digested is called as cud.
5. Cellulose, an important plant based carbohydrate is broken down & digested  by the cellulose digesting bacteria present in the rumen.

Reticulum:

1. It is the second chamber of the stomach.
2. From the rumen the cud enters the reticulum.
3. Here, the cud is brought back to the mouth in small lumps to chew it properly. This process of rechewing of cud is called as rumination.
4. Saliva is mixed with the food & the food is rechewed.
5. The food enters the third chamber.

Omasum:

1. It is the third & smallest chamber of the stomach.
2. Here, the food is broken down into small pieces.

Abomasum:

1. It is the fourth chamber of the stomach.
2. Here, hydochloric acid & gastric juices are secreted to digest the food.
3. From here the food reaches the caecum.

Caecum:

1. It is a sac like structure present between small and large intestine.
2. in some animals like horses, rabbits, cellulose may be digested here. 

Small Intestine:

The digested food now passes into the small intestine for absorption and assimilation.

Large intestine:

The undigested food passes through the large intestine, where water & minerals are abosrbed.

The undigested food is stored as waste & egested from the body.

*Humans caanot digest cellulose as they don't have cellulose digesting bacteria.