CBSE Class 9 Science Advanced Biology Fundamental Unit of Life Very Short Answer Questions Set 02

Very Short Answer Type

Question 1. A person takes concentrated solution of salt, after sometime, he starts vomiting. What is the phenomenon responsible for such situation ? Explain.
Answer:
The phenomenon is osmosis (exosmosis).
The concentrated salt solution in the stomach is hypertonic to the cells lining the stomach. Water moves out of these cells by osmosis into the salt solution, which irritates the stomach lining and makes the person vomit.
In simple words: Osmosis pulls water out of the cells into the strong salt solution, and this causes vomiting.

Teacher's Note:
1. Never drink strong salt solution: it is harmful because it draws water out of the body cells.
2. Name the process first and then explain it.

Question 2. Write down the definition of cell.
Answer:
A cell is the smallest unit of structure and function of living organisms.
In simple words: A cell is the basic building and working unit of life.

Teacher's Note:
1. Use the words 'structural and functional unit'.
2. Add that all living things are made of cells.

Question 3. Who wrote micrographia.
Answer:
Robert Hooke wrote Micrographia (1665), in which he described the cells he saw in a slice of cork.
In simple words: Robert Hooke wrote Micrographia.

Teacher's Note:
1. Hooke gave the name 'cell' in this book.
2. Link the book with the year 1665.

Question 4. Define omnis cellula e cellulae.
Answer:
Omnis cellula e cellula is a Latin saying (the book prints it as 'e cellulae') that was given by Rudolf Virchow. It means "every cell arises from a pre-existing cell": new cells are formed only by the division of old cells.
In simple words: It means that all cells come from cells that already exist.

Teacher's Note:
1. This is the third point of the cell theory.
2. It was Virchow's addition to the theory of Schleiden and Schwann.

Question 5. Define prokaryotic cell.
Answer:
A prokaryotic cell is a primitive cell with no true nucleus, that is, it has no nuclear membrane and no nucleolus, and no membrane-bound organelles. Its DNA lies in the cytoplasm as a nucleoid. Bacteria are examples.
In simple words: A prokaryotic cell has no real nucleus.

Teacher's Note:
1. Pro means before and karyon means nucleus.
2. Bacteria and blue-green algae are prokaryotes.

Question 6. Give one example of dedifferentiated cell.
Answer:
The cork cambium (phellogen) of a woody stem is formed when mature, permanent cells of the cortex go back to the dividing state. Cells of the callus formed at a wound and the cambium formed between vascular bundles are other examples.
In simple words: Mature cells that start dividing again, like cork cambium cells, are dedifferentiated.

Teacher's Note:
1. Dedifferentiation often happens during regeneration.
2. These cells become meristematic once more.

Question 7. Give one-one example of spindle shape cell, discoidal and branched cell.
Answer:
Spindle-shaped cell: muscle cell.
Discoidal cell: red blood cell (RBC).
Branched cell: pigment cell (melanocyte) or nerve cell.
In simple words: Muscle cell is spindle-shaped, RBC is disc-shaped and a pigment cell is branched.

Teacher's Note:
1. Learn the six shapes in the chapter figure.
2. Shape and function are closely connected.

Question 8. Write down the name of largest plant cell.
Answer:
The chapter's answer is the hemp fibre, the longest cell in plants. (The single-celled alga Acetabularia is also a very large plant-like cell, several centimetres long.)
In simple words: The hemp fibre is the largest (longest) plant cell in this chapter.

Teacher's Note:
1. Recall the longest animal cell: the nerve cell.
2. The very largest cell of all is the ostrich egg.

Question 9. Write down the name of smallest cell of human body.
Answer:
The sperm is the smallest cell of the human body by volume. (Many books give the red blood cell, about 7 µm in diameter, as the smallest cell.)
In simple words: The sperm is the smallest human cell.

Teacher's Note:
1. The largest human cell is the egg (ovum).
2. Both red blood cells and sperm are very small.

Question 10. Define protoplast.
Answer:
The protoplast is the living part of a plant cell lying inside the cell wall. It consists of the plasma membrane and the protoplasm (nucleus and cytoplasm).
In simple words: The protoplast is the cell without its cell wall.

Teacher's Note:
1. Plant cell = protoplast + cell wall.
2. Check the flow chart of the cell components.

Question 11. What is the composition of protoplasm ?
Answer:
Protoplasm is made of the nucleoplasm (the protoplasm inside the nucleus) and the cytoplasm (the protoplasm outside the nucleus).
Chemically it is mostly water with proteins, carbohydrates, lipids, nucleic acids and mineral salts.
In simple words: Protoplasm = nucleoplasm + cytoplasm.

Teacher's Note:
1. Protoplasm is the living part of the cell.
2. Use the plus sign in your answer.

Question 12. Who gave the fluid mosaic model of plasma membrane ?
Answer:
Singer and Nicolson (1972) gave the fluid mosaic model of the plasma membrane.
In simple words: Singer and Nicolson proposed the fluid mosaic model.

Teacher's Note:
1. In it, proteins float in a fluid bilayer of lipids.
2. This is the accepted model today.

Question 13. What is osmosis ?
Answer:
Osmosis is the movement of water (solvent) through a semipermeable membrane from a solution of lower concentration to a solution of higher concentration. It is also called the diffusion of the solvent.
In simple words: Osmosis is the passage of water through a membrane toward the more concentrated solution.

Teacher's Note:
1. It needs no energy: it is passive.
2. Water goes toward the side with more solute.

Question 14. Which cell organelle is called as the head quarter of cell ?
Answer:
The nucleus is called the headquarters of the cell, because it controls all the activities of the cell.
In simple words: The nucleus controls the cell.

Teacher's Note:
1. The nucleus is also called the control centre.
2. It holds the genetic material.

Question 15. Which organelle controls osmotic pressure in a cell ?
Answer:
The vacuole controls the osmotic pressure of a cell.
In simple words: The vacuole controls the cell's osmotic pressure.

Teacher's Note:
1. The vacuole is bounded by the tonoplast.
2. It is large in plant cells.