[Quiz] NCERT Class 7 Biology Chapter -1 Nutrition in Animals

The inner lining of the stomach secretes mucus, hydrochloric acid and digestive juices. Mucus protects the lining of the stomach. The hydrochloric acid kills many bacteria that enter along with the food and makes the medium in the stomach acidic and helps the digestive juices to act. Digestive juices break down the proteins into simpler substances. The digested food can now pass into the blood vessels through the wall of the small intestine. This process is called absorption. The large intestine absorbs water and some salts from the undigested food material. The liver is the largest gland in the body. It secretes bile juice that is stored in a sac called the gallbladder. Bile plays an important role in the digestion of fats.

It is the microscopic unicellular organism found in pond water which keeps changing its shape and position constantly. It has a cell membrane, a rounded, dense nucleus and many small bubble-like vacuoles in its cytoplasm. The amoeba is a tiny, one-celled organism. You need a microscope to see most amoebas - the largest are only about 1 mm across. Amoebas live in fresh water (like puddle and ponds), in salt water, in wet soil, and in animals (including people). There are many different types of amoebas. The name amoeba comes from the Greek word amoibe, which means change. (Amoeba is sometimes spelled ameba.)

1. Cell membrane - the thin layer of protein and fat that surrounds the amoeba; it allows some substances to pass into the cell. and blocks other substances.

2. Contractile vacuole - a cavity within the amoeba that excretes excess water and waste; the waste is brought to the cell membrane and is then eliminated from the amoeba.

3. Cytoplasm (ectoplasm and endoplasm) - a jelly-like material that fills most of the cell; the organelles (like the nucleus) are surrounded by cytoplasm.

4. Food vacuole - a cavity within the amoeba in which food is digested (broken down in order to be absorbed by the amoeba).

5. Nucleus - the major organelle of the amoeba, located centrally; it controls reproduction (it contains the chromosomes) and many other important functions (including eating and growth).

6. Pseudopods - temporary "feet" that the amoeba uses to move around and to engulf food. An amoeba consists of a single blobby cell surrounded by a porous cell membrane. The amoeba "breathes" using this membrane - oxygen gas from the water passes in to the amoeba through the cell membrane and carbon dioxide gas leaves through it. A complex, jelly-like series of folded membranes called cytoplasm fills most of the cell. A large, disk-shaped nucleus within the amoeba controls the growth and reproduction of the amoeba.