Dear students, prepare for biology class 9th chapter 5 long questions. These important long questions are carefully added to get you best preparation for your 9th class biology ch. 5 exams.
0
Our database contains a total of 0 questions for biology Short Questions. You’ll prepare using this huge databank.
Question: 1
Define reproduction. Describe its importance in life.
Answer: 1
1-21The most basic characteristic of life is reproduction.
Definition
It is a biological process in living things by which they produce their young ones which are similar to parents.
Levels of Reproduction
Reproduction occurs at different levels of organization.
(i) Parts of the cell such as the chromosomes produce new chromosomes.
(ii) Cells then produce new cells
(iii) Individuals produce off springs like themselves.
Reproduction for continuation of life
Rudolf Virchow proposed an important biological principle that all cells come from pre¬existing cells. This principle tells us that the continuation of life, including all aspects of reproduction, is based on the reproduction of cells. We commonly refer cellular reproduction as cell division and it is a part of whole life of a cell i.e. cell cycle.
Question: 2
Define inter-phase. Explain the stages of inter-phase.
Answer: 2
2-21Inter-phase is the time when a cell's metabolic activity is very high, as it performs its various functions. Stages of interphase
It is divided into three phases.
G1 (first gap)
S (synthesis)
G2 (second gap)
G1 Phase
After its production, a cell starts its cell cycle in G1 phase. During this phase,
(i) The cell increases its supply of proteins,
(ii) Cell increases the number of its organelles (such as mitochondria, ribosomes)
(iii)Cell grows in size.
(iv)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.
S Phase
In this phase, DNA replication takes place, as a result the cell duplicates its chromosomes. As a result, each chromosome consists of two sister chromatids.
G2 Phase
In the G2 phase, the cell prepares proteins that are essential for mitosis, mainly for the production of spindle fibers.
After the G2 phase of inter-phase, the cell enters in the division phase i.e. M phase. It is characterized by mitosis, in which the cell divides into the two daughter cells.
Question: 3
What is mitosis? Describe its Discovery and phases.
Answer: 3
3-21Inter-phase is the time when a cell's metabolic activity is very high, as it performs its various functions. Stages of interphase
It is divided into three phases.
G1 (first gap)
S (synthesis)
G2 (second gap)
G1 Phase
After its production, a cell starts its cell cycle in G1 phase. During this phase,
(i) The cell increases its supply of proteins,
(ii) Cell increases the number of its organelles (such as mitochondria, ribosomes)
(iii)Cell grows in size.
(iv)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.
S Phase
In this phase, DNA replication takes place, as a result the cell duplicates its chromosomes. As a result, each chromosome consists of two sister chromatids.
G2 Phase
In the G2 phase, the cell prepares proteins that are essential for mitosis, mainly for the production of spindle fibers.
After the G2 phase of inter-phase, the cell enters in the division phase i.e. M phase. It is characterized by mitosis, in which the cell divides into the two daughter cells.
Question: 4
Define meiosis and explain its phases in detail.
Answer: 4
4-21
Question: 5
Describe significance of meiosis?
Answer: 5
5-21. Introduction
The significance of meiosis for reproduction and inheritance was described in 1980 by German biologist August Weizmann.
(i) Maintenance of chromosome number
August Weizmann noted that meiosis was necessary not only to maintain the number of chromosomes in the next generation but also to produce variations in next generation.
(ii) Meiosis for sexual reproduction of Eukaryotas
Meiosis is essential for sexual reproduction and therefore occurs in all eukaryotes including single celled organisms that reproduce sexually. Meiosis does not occur in prokaryotes, which reproduce asexually by binary fission.
(iii) Meiosis in humans
In human diploid gametes, mother cells or germ line cells undergo meiosis to produce haploid gametes. Male and female gametes unite to form diploid zygote which undergoes repeated mitosis and develops into the new diploid human.
(iv) Gamete formation in fungi and protozoa
Many haploid fungi and protozoa produce haploid gametes through mitosis.
(v) Meiosis in plants
Plants' life cycle shows alternation of generation. The cells of the diploid sporophyte generation undergo meiosis to produce haploid spores, which grow into haploid gametophyte generation. The haploid gametophyte generation produces haploid gametes through mitosis. The gametes combine to produce the diploid zygote. The zygote undergoes mitosis to become the diploid saprophyte.
(vi) Meiosis as a source of genetic variations
The chromosome pairs of each parent undergo crossing over during meiosis. So daughter cells i.e. gametes have genetic variations. When gametes fuse and form zygote; its genetic make-up is different from both parents. Thus meiosis allows a species to bring variations which help organisms to adapt to the changes in environment.
Question: 6
Write a note on necrosis.
Answer: 6
6-21
Question: 7
What is apoptosis? What happens in it? Describe its importance.
Answer: 7
7-21"Between 50 billion to 70 billion cells die each day due to apoptosis in an adult human". Apoptosis is one of the main types of programmed cell death.
Events of apoptosis
Following is the series of events in apoptosis:
(i) Cell shrinks and becomes rounded due to the breakdown of the cytoskeleton by enzymes.
(ii) Chromatin undergoes condensation and the nuclear envelope breaks. (iii)In this way, nucleus spreads in the form of several discrete chromatin bodies.
(iv)The cell membrane makes irregular buds known as blabs.
(v) The blebs break off from the cell and are now called apoptotic bodies, which are then phagocytosed by other cells.
Causes of apoptosis
Apoptosis can occur when a cell is damaged, or undergoes stress conditions.
Significance of apoptosis(i) Removal of damaged cell
Apoptosis removes the damaged cell, preventing it from getting further nutrients or to prevent the spread of infection.
(ii) Differentiation of fingers and toes in embryo
Apoptosis generally gives advantages during development. For example, during the formation of fingers, the cells between them undergo apoptosis and the digits separate.
Question: 8
Q no: 5 (A) What is apoptosis? Describe Series of events in Apoptosis.
Answer: 8
8-21Apoptosis is one of the main types of programmed cell death. During apaptosis cell shrinks and become rounded due to the breakdown of cytoskeleton by enzymes. It chromation undergoes condensation and nuclear encelaps breaks . In this way nuclesus spread in the from of several discrete chormatin bosies . cell memberne makes irregular buds known as blebs . Blebs breake from the cell and one know called apoplotic bodies . Which are than phagocylosed by their cells.during the formation of fingers. The cell between them under go apaptosis and the digit separate
Apoptosis con occur when a cell is demaged or endergoes stress condition apoptosis removes the demaged cell. preventing oit from getting further nutrients or to prevent this spread of infection Apaptosis also gives advantages during development. For Example
Question: 9
Q no: (B) What is cell cycle and describe all the phases of <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859120920584447283643">interphase</gwmw> in detail.
Answer: 9
9-21Cell cycle: Cell cycle is series of event from the time a cell is produced until . It completes mitosis and produce new cell. Cell cycle consist of two major phase interphase and mitotic phase. is a relatively short peviod of cell cycle . It alternates with the much longer interphase where cell prepare itself for division.Interphase :Interphase is the time when a cell metabalic activity is very high as its perform itsvarious function it is divided into three phase .
Mitotic Phase:
G1 phase:
After is reproduction a cell starts is cellcycle in G1 phase During this phase cell increase its supply of proteins increase the number of its organells or grow in size. This phase is also marked by the synthesis of various enzymes that are required in next phase
S phase:
In this phase cell duplicates its choromosomes . As a result each chromosomes. As a result each chromosome consist of two writerchronatids .
G2 phase:
In The G2phase cell prepares proteins that are essential for mitosis mainly for the production of spindle fibres .
Go Phase:
In multicellular eukaryotic cell enter Go phase from G1 and stop dividing some one remain in Go for indefinite perioud of neurons.
Question: 10
Q no<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859150051247305654841">:</gwmw>6 (A) Explain the changes which take place during prophase of mitosis.
Answer: 10
10-21Prophase of mitosis:
Normally the genetic materials in nucleus is in a loose thread-like form called chromatin At the onset of prophase chromatin condenses into highly ordered structures called chromosome . Sine the genetic materials has already been duplicatied either in S phase each chromatids . bound together at the same centromere Each chromosomes also has kinetochore at centomere . There are two centrioles . Eachcentriols duplicae and thus two daughter centrosomes are formed Both centrosomes migrate to the opposite poles of cell . The microtubules thus formed are called spindle fibres . complete set of rpindle fibres is known as mitotic spindle . By this time nucleaslus and nuclear envelops have degraded and pindle fibres have invaded the central phase.
Question: 11
Q no: (B) Write short note Necrosis.
Answer: 11
11-21Necrosis is the accidental death of cell and living tissues. Necrosis is less sequential than apoptosis there are many cause of necrosis including injury inflection concer ect . Necrosis may occur when a cell is given hypoxiaenviroments
During necrasis there is a release of special enzymes from lysosomes uysosomes enzymes break cellulan components and may also may be released outsides cell to break surrounding cell . Cells that necrosis may also release harmful chemicals that damage other cells.
Question: 12
Q no: 7 (A) Describe the Significance of Meiosos Meiosis:<div></div>
Answer: 12
12-21The significance of meisos for reproduction and inheritance was described in 1890 by german biologsis August weismann .
Maintenance of the chromosomes number in next generation:
Meiosis is essential for sexual reprodution in humans diplaid gemete mather cells ot germ line cell undergo meisosis to produce haploid gemeter male and female gemetes unite to form diploid zygoat . Which undergoer repeated mitosis and develops into a new dipliods Humans.
Production of variation in next generation:
The chromomes paios of each parent undergo crossing over during meiosis. So daughter cell gametes have genetic vaiation . when gemeter fuse and form zygote
ERRORS In MEIOSIS:
During anaphase chromoseomes separated and go to opposite poles with during anaphase anaphase 2 sister chromosomes seprated . It is called
Disjunction:
Some time the seperation is not normal and it is called NoN Disjunction.
It result abnormalchromosomes number in next generation for example 47 or 45 chromosomes in humans
Question: 13
Describe <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859202853488600818329">prophase</gwmw>of Meiosis:
Answer: 13
13-21Question: 14
Define cell cycle . Explain its phases
Answer: 14
14-21Cell cycle : It is the series of events from the time a cell is produced until it completes mitosis and produces new cell
Phases of cell cycle :
Phases of cell cycle :
It consists of two major parts
1: Interphase : The phase of cell cycle in which n a cell's metabolic activity is very high , as it performs its various functions but it is non-dividing phase of cell cycle
2: Mitotic phase : Mitotic phase is relatively short period of cell cycle . It alternates with much longer interphase where cell prepares itself for division
Interphase last for at least 90% of the total time required for the cell cycle
-Division of interphase : It is divided into three phases G1 (first gap) S(synthesis) and G2(Second gap)
-G1 phase : During this phase , a cell increases its supply of proteins and increase the number of its organelles (such as Ribosomes , Mitochondria ) and grows in size and synthesize various enzyme that are required in next phase i-e S phase for the duplication of chromosomes
Question: 15
Define mitosis . Explain its phases
Answer: 15
15-21Mitosis : The type of cell division in which a cell divides into two daughter cells . Each with a same number of chromosomes as were present in parent cell
Discovery of Mitosis: In 1880's German biologist , Walther Flemming discovered mitosis
Occurrence of mitosis : Mitosis occurs only in eukaryotic cell . In multicellular organisms the somatic cells undergo mitosis
Binary fission : In prokaryotic cell , it is a process in which one organism divide into two organisms
Phases of mitosis : Mitosis is complex it has two major phases
1: Karyokinesis : The division of nucleus is called Karyokinesis
2: Cytokinesis : The division of cytoplasm is called cytokinesis
KaryokinesisIt is further divided into four phases
1: Prophase
2: Metaphase
3: Anaphase
4: Telophase
1: Prophase :
Chromatin : Normally the genetic material in nucleus is in loose thread like form called chromatin
Chromosomes : (Chromo=color , Soma= body )
During cell division chromatin condenses into highly ordered structure called chromosomes
Kinetochore : It is a complex protein structure that is the point where spindle fibers attach
Centrosomes : The two centrioles are collectively called centrosomes
Spindle fiber : Mitochondria join together and form spindle fibers
Mitotic fibers : Complete set of spindle fibers is called mitotic fibers
Question: 16
What is the singnificance of mitosis ?
Answer: 16
16-21Importance of mitosis is maintenance of chromosomal set following are the occasions in lives organisms where mitosis happen
Development and growth :
The number of cell within an organism increase by mitosis . This is the basic of development of multicellular body from single cell i-e zygote and also the basis of the growth of multicellular body
Question: 17
What happens if errors in mitosis occurs ?
Answer: 17
17-21Errors in mitosis : Errors in the control of mitosis may cause cancer . All cells have genes that controls the timing and number of mitosis
Tumor: Sometimes mutation occur in such genes and cells contain to divide its result in growth of abnormal cells called tumors
Benign Tumors : A ling as the tumors remain in their original location they are called Benign Tumors
Malignant Tumors/ Cancerous Tumors
If the Benign Tumors invade other tissues they are called Malignant
Question: 18
Define meiosis . Explain its phase
Answer: 18
18-21Crossing over : After the formation of chiasmata the non-sister chromatids of homologous chromosomes exchange their segments and the phenomenon is known as crossing over
Process :
1: Chromosomes condense further the nuclei envelope disappear and nuclear envelope disintegrates
2: Centrioles which were duplicated during interphase migrate to the two poles and form spindle fibers
3: The kinetochore spindle fibers attach with kinetochore of chromosomes
4: Two kinetochore spindle fibers attach with a pair of chromosomes
Metaphase 1 : The pairs of homologous chromosomes align along equatorial plane forming the metaphase plate
3: Anaphase 1: kinetochore spindle fibers shorten . It results in pulling apart the chromosomes of each pair .Since one chromosomes is pulled towards one pole , two haploid sets are formed . Each chromosomes still contains a pair of sister chromatids
4: Telophase 1: Chromosomes arrive at the poles . Each pole now has the number of chromosomes each chromosomes still consists of two chromatids . Spindle network disappears , and nucleus envelope is formed around each haploid set . Chromosomes uncoil back into chromatin
a) Cytokinesis : The pinching of cell membrane in animal cells or the formation of cell wall in plant cells is called cytokinesis . It occurs and creation of two haploid daughter cells is completed
Question: 19
What is the significance of meiosis ?
Answer: 19
19-21The significance of meiosis for reproduction and inheritance was described 1890 by German biologists August Weismann . He pointed out that meiosis was necessary not only to maintain the number of chromosomes in the next generation but also to produce variations in next generation
1: Maintenance of chromosomes number in next generation :
Meiosis is essential for sexual reproduction
In humans : Meiosis is essential for sexual reproduction . In human diploid gamete-mother cells or germ line cells undergo repeated mitosis and develops into a new diploid human
In fungi and protozoans : Many haploid fungi and protozoans produce haploid gametes through mitosis
Question: 20
What happens if errors in meiosis occur?
Answer: 20
20-21During anaphase 1 , homologous chromosomes separate and go to the opposite poles while during anaphase 2 sister chromosomes separate it is called disjunction
Example:
In normal separation 46 chromosomes are present
Non disjunction :
Sometimes separation is not normal and it is called non disjunction
Increasing in number of chromosomes cause abnormality because meiosis results in the production of gametes which have either more or less than the normal number of chromosomes in the next generation
Question: 21
Write note on<div>1: Apoptosis 2: Necrosis</div>
Answer: 21
21-21Apoptosis and Necrosis are two phenomenon of cell death
1:Apoptosis:
Apoptosis is one of the main types of programmed cell death , and involves a series of biochemical events . This process is controlled by extracellular signals (e.g hormones ) or intracellular signals (e.g good deprivation , viral infection
