9th Biology Chapter # 5 All Punjab Board Papers | 5 Years Old Board Papers Short questions | Repeated short questions in all Board Papers

   CHAPTER No. 5

1.                 Define cell cycle.       

Ans.     The cell cycle is the series of events from the time a cell is produced until it completes mitosis and produces new cells.

2.                  Name two major phases of cell cycle and which phase is divided into three. Name these phases.        

Ans.     Major Phases are interphase and mitotic phase. Interphase is divided three phases

            (A) G1  (First gap)              (B) S (synthesis)    (C) G2  (Second gap)

3.                  Name two major phases of cell cycle.

Ans.     (A) Interphase             (B) Mitotic Phase

4.                  What is G-I phase./ Write the importance of G1 phase.  

Ans.     G 1-phase:  During this phase, cell increases its supply of proteins and ribosomes and grows in size. This phase is also marked by the synthesis of various enzymes, that are required in the next phase i.e. S-phase for the duplication of chromosomes.

5.                  Explain S-Phase in cell cycle./ What changes occurs in S-phase.

Ans.     S-Phase:   In this phase, cell duplicates its chromosomes.  As a result each chromosome consists of two sister chromatics.

6.                  What is main function during G2 phase of cell cycle?      

Ans.     Cell prepares proteins that are essential for mitosis mainly for the production of spindle fibers.

7.                  What do you know about G₀ phase?                                             

Ans.     In multicellular eukaryotes, cell enter Go phase from GI and stop dividing. Some cells remain in Go for indefinite period e.g Neurons, Some cells enter semi-permanently e.g cells of liver and kidney. Some cells not enter in Go and continue to divide e.g epithelial cells.

8.                 By whom and when was the process of mitosis discovered?

Ans.     The process of mitosis was discovered by a German biologist Walther Flemming in 1880’s.

9.                  Define mitosis. In which cells does it occur?                                  

Ans:     Mitosis is the type of cell division in which a cell divides into two daughter cells, each with the same number of chromosomes as were present in parent cell.

            Mitosis occurs only in eukaryotic cells.

10.              What is binary fission?

Ans.     Prokaryotic cell undergo a process similar to mitosis called binary fission.

11.             What are somatic cells?                                                       

Ans.     Somatic cells are those cells which form the body of organisms. Somatic cells undergo mitosis.

12.              What is the difference between somatic cells and germ line cells?

Ans.                

Somatic Cells	Germline Cells
These cells form the body of organisms.	These cells form the gametes.
These undergo mitosis.	These undergo meiosis.

13.              Differentiate between karyokinesis and cytokinesis./  Define Karyokinesis.

Ans:    

Karyokinesis	Cytokinesis
It is the division of nucleus	It is the division of cytoplasm

14.              Write the name of two major phases during mitosis.

Ans.     These are karyokinesis, cytokinesis.

15.              Differentiate between chromatin and chromosomes:

Ans:    

Chromatin	Chromosomes
Normally the genetic material in nucleus is in a loose thread like form called chromatin.	At the onset of prophase, chromatin condenses into highly ordered structures called chromosomes.

16.              What is mitotic Spindle?

Ans.     In the cell two centrosomes give rise microtubules called spindle fibers and complete set of spindle fibers is called mitotic spindle

17.              What is the role of telophase in mitosis?

Ans:     Telophase is the reversal of prophase. A new nuclear envelop forms around each set of separated chromosomes. Both sets of chromosomes, now surrounded by new nuclear envelopes, unfold back into chromatin.

18.              What are Phragmoplast?     Or        What is meant by phragmoplast?

Ans.     During cytoplasm in plant cells, vesicles derived from the Golgi apparatus move to the middle of cell and fuse to form a membrane-bound disc called cell plate or phragmoplast.

19.              What is meant by cytokinesis? How this process is carried out in animal’s cells?          /  How does cytokinesis occur in animal cells?    Or        Division of cytoplasm.         

Ans:     Cytokinesis: The division of cytoplasm known as cytokinesis.

            Cytokinesis in animals: In animal cells, cytokinesis occurs by a process known as cleavage. A cleavage furrow develops where metaphase plate used to be. The furrow deepens and eventually pinches the parent cell into two daughter cells.

20.              How does cytokinesis differ in animal and plant cells?/ How cytokinesis occur in plant cell.                                                             

Ans:     In animal cells, cytokinesis occurs by a process known as cleavage. According to this cleavage furrow develops where the metaphase plate used to be. The furrow deepens and eventually pinches the parent cell into two daughter cells.

            In plant cells, vesicles derived from the Golgi apparatus move to the middle of cell and fuse to form a membrane-bounded disc called cell plate or phragmoplast. The plate grows outward and more vesicles fuse with it. Finally membranes of cell plate fuse with plasma membrane and its contents join the parental cell wall.

21.              What is meant by development and growth?

Ans:     The number of cells within an organism increase by mitosis. This is the basic of the development of a multicellular body from a single cell i.e. zygote and also the basis of the growth of multicellular body.

22.              Write two significances of mitosis?

Ans.     1- The organisms can replace their body parts e.g. skin and digestive tract where the cells are constantly sloughed off and replace by new cells.

              2- Some organisms can regenerate its lost arm through mitosis.

23.            What is meant by regeneration? Give an example.  (2 Time) (2017)

Ans.     It is the process of the replacement of lost body parts in organisms e.g. sea stars regenerates its lost arm through mitosis.

24.              Write budding process in hydra./ Explain how Asexual reproduction occur in hydra?

Ans:     The cells at the surface of hydra undergo mitosis and form a mass called bud. Mitosis continues in the cells of bud and it grows into a new individual.

25.              What is meant by tumor?                                                   

Ans.     Sometimes mutations occur in such genes and cell continues to divide. It results in growth of abnormal cell called tumors.

26.              What is the difference between Benign and Malignant?/ What are benign tumors?/  What is Malignant Tumor?                           

Ans.    

Benign Tumor	Malignant Tumor
As long as the tumors remain in their original location, they are called benign Tumor.	If the tumors invade other tissues they are called malignant tumor.

27.             What is meant by metastasis?                                          

Ans.     When tumors send cancer cells to other parts in the body where new tumors may form this is called metastasis

28.              Define meiosis. Name the scientist who discovered the meiosis?

Ans.     Meiosis:  Meiosis is a process by which a diploid (2n) eukaryotic cell divides to generate four haploid (1n) daughter cells and chromosomes become half in daughter cells. Meiosis was discovered by German biologist Oscar Hertwig in 1876.

29.              Differentiate Diploid and Haploid cells.

Ans.    

Diploid Cell	Haploid Cell
Each daughter cell with same number of chromosomes as present in parent cell.	Each daughter cell with no same number of chromosomes as in parent cell.
Diploid means the cells in which chromosomes are in pairs (homologous pairs) of chromosomes	Haploid means the cells with   half the number of chromosomes i.e. chromosomes are not in the form of pairs.

30.             Give two differences between mitosis and meiosis.     (2 Time) (2017)

Ans.    

Mitosis	Meiosis
(i)  It is a type of cell division, in which no of chromosomes remains constant in daughter cell as in the parent cell.	(i)  It is a cell division in which number of chromosomes are reduce to half in daughter cells as compared to parent cell.
(ii)  It occurs in both haploid as well as diploid cell.	(ii)  It occur only in diploid cells.
In this cell division parent cell is divided into two daughter diploid cell.	(iii)  In this cell division on parent cell is divided into four haploid cells.

31.              Define meiosis and mitosis.

Ans:     Mitosis: Mitosis is the type of cell division in which a cell divides into two daughter cells, each with the same number of chromosomes as were present in parent cell.

            Meiosis: It is the process by which one diploid (2n) eukaryotic cell divides to generate four haploid (1n) daughter cells.

32.              What is crossing over? Give its one benefit.          

Ans.     The non-sister chromatids of homologous chromosomes exchange their segment and the phenomenon is known as crossing over.

33.              What is the importance of crossing over in Meiosis?

Ans.     The exchange of segments results in the recombination of genetic information. After crossing over each pair of homologous chromosomes remain as a bivalent.

34.              Define Synapsis.                                                        

Ans.     The homologous chromosomes line up with each other and form pairs by a process called synapsis.

35.              Define Chiasmata.                                                    

Ans.     The two non-sister chromatids of homologous chromosomes join each other at certain points along their lengths. These points of attachment are called chiasmata.

36.              What changes are placed in telophase during meiosis?

Ans:     .Each pole now has half the number of chromosomes but each chromosomes still consists of two chromatids. Spindle network disappears, and nuclear envelop is formed around each haploid set. Chromosomes uncoil back into chromatin.  

37.              Give one advantage of meiosis division.

Ans.     Meiosis was necessary not only to maintain the number of chromosomes in next generation but also to produce variations in next generation.

38.              What is difference between disjunction and non-disjunction?/ What is meant by disjunction in meiosis?                                             

Ans.     Disjunction is a normal separation of chromosomes in meiosis while abnormal separation of chromosomes in meiosis is non-disjunction.

39.              What is meant by apoptosis?                                  

Ans:     Apoptosis is one of the main types of programmed cell death. During apoptosis, cell shrinks and becomes rounded due to the breakdown of cytoskeleton by enzymes.

40.              Define "blebs". What is another name of these?  

Ans:     During apoptosis the cell membrane makes irregular buds known as blebs. Blebs break off from the cell and are now called apoptotic bodies.

41.              Differentiate between blebs and apoptotic bodies.

Ans.     Cell membrane makes irregular buds is called blebs. Blebs break off from the cell and are now called apoptotic bodies.

42.              What is the major advantage of apoptosis during the organism’s life cycle?

Ans.     Duration the formation of fingers the cells b/w them under go apoptosis and the digits separate.

43.              What is necrosis?/ Write own its two causes./ Write the causes of necrosis.   

Ans:     Necrosis is the accidental death of cells and living tissues. There are many causes of necrosis including injury, infection, cancer etc.

44.              Differentiate between necrosis and apoptosis.

Ans:    

Necrosis	Apoptosis
Necrosis is the accidental death of cells and living tissues.	Apoptosis is one of the main types of programmed cell death.