NCERT Solutions for Class 9 Science Chapter 5 The fundamental unit of life in PDF form to free download. 9 Science Solutions for all chapter are given in PDF. Download NCERT Solutions for other subjects here.
NCERT Solutions for Class 9 Science Chapter 5
Class 9 Science – Biology
The Fundamental Unit of Life
- Question 1:
Why is the cell called the structural and functional unit of life?
- Answer 1:
A cell is a smallest part of the living organisms which is fully alive and is capable of performing basic processes of life like, reproduction and respiration, therefore, it is called the structural and functional unit of life.
- Question 2:
Which functions are performed by a single cell organism like amoeba?
- Answer 2:
A single cell takes in food, excrete waste, move, grow and reproduce.
- Question 3:
Who discovered the cell and how?
- Answer 3:
Robert Hooke saw the cork which resembled the structure of a honey comb consisting of many little compartments. He observed these through a microscope. He called these boxes as cell.
- Question 4:
(a) Name a single cell which may constitute a whole organism. What are they called?
(b) Every multicellular organism has come from a single cell. Justify the statement.
- Answer 4:
(a) Amoeba, They are called Unicellular organism.
(b) Single cell forms a zygote which is first cell formed after fertilization. It further leads to the formation of large number of cells by cell division.
- Question 5:
Why is plasma membrane called a selective permeable membrane?
- Answer 5:
It is because it allows only certain material to pass through it and not all the materials.
- Question 6:
How do substances like carbon dioxide and water moves in and out of the cell? Discuss.
- Answer 6:
It takes place through diffusion from higher concentration to lower concentration across a cell membrane.
- Question 7:
What will happen when a human red blood cells is placed in hypertonic salt/sugar solution?
- Answer 7:
It will shrink, i.e., plasmolysis will take place.
- Question 8:
What is the difference between diffusion and osmosis?
- Answer 8:
In diffusion movement of ions, solute, solvent or gases take place where in osmosis only movement of solvent take place. In diffusion semipermeable membrane is not involved where as in osmosis, it is involved.
- Question 9:
Can you name the two organelles which contains their own genetic material?
- Answer 9:
(i) Mitochondria (ii) Chloroplast
- Question 10:
Why are Lysosomes known as suicide bags?
- Answer 10:
When the covering membrane breaks, Lysosomes spill digestive enzyme which digest the organic materials and will kiss cells, therefore they are called suicide bags.
- Question 11:
Where are proteins synthesized inside the cell?
- Answer 11:
Packaging, storage and dispatching of the materials, synthesized inside the cell will not take place.
- Question 12:
Which organelle is known as the powerhouse of the cell? Why?
- Answer 12:
Mitochondria, because it provides energy in the form of ATP for all cellular activities.
- Question 13:
Why are stem cell used in treatment of severe immunodeficiency disorder (SCID) in the children? Give three reasons.
- Answer 13:
(i) These are capable of dividing for long periods to generate replacement for the cell which that cannot produce adenosine deaminase.
(ii) Stem cells can trigger immune response.
(iii) Stem cells can differentiate into white blood cells against the infectious diseases.
- Question 14:
State the difference between mitochondria and plastid.
- Answer 14:
(i) It is a double membrane structure.
(ii) It releases energy in the form of ATP.
(iii) It is the power house of the cell.
(i) It is a semi-autonomous structure.
(ii) It provides colour to the plant parts.
(iii) It is the Kitchen of the plants cell.
- Question 15:
Why is saline water gargles are useful in sore throat?
- Answer 15:
Saline water is a hypertonic solution exosmosises will occur and common salt is an antiviral agent.