Chapter – 2 : Continuity of Life | Chapter Solution Class 10

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Book Name : Life Science And Environment
Subject : Life Science
Class : 10 (Madhyamik)
Publisher : Santra Publisher Pvt. Ltd
Unit Name : Continuity of Life

Multiple Choice Questions

Question 1

The chromosome number of a gamete of man is

  1. 64
  2. 32
  3. 46
  4. 23

Answer

23

Explanation

Gametes are haploid cells, meaning they have half the number of chromosomes as a somatic cell. Somatic cells in humans have 46 chromosomes, while gametes have 23 chromosomes.

Question 2

Direct cell division is known as

  1. Mitosis
  2. Meiosis
  3. Cytokinesis.
  4. Amitosis

Answer

Amitosis

Explanation

Amitosis is a type of cell division that does not involve the separation of chromosomes. It is a simpler form of cell division than mitosis or meiosis, and it is often seen in unicellular organisms.

Question 3

Reduction division is formed in

  1. Mitosis.
  2. Amitosise.
  3. Meiosis.
  4. Cytokinesis

Answer

Meiosis

Explanation

Reduction division is a process that occurs during meiosis, a type of cell division that produces gametes. During reduction division, the number of chromosomes is reduced by half. This ensures that the gametes have the correct number of chromosomes to combine with another gamete to form a zygote.

Question 4

In which of the stage of mitosis cell division does the nuclear membrane disappear?

  1. Interphase.
  2. Anaphaseeis
  3. Prophase.
  4. Telophase

Answer

Prophase

Explanation

During prophase, the chromosomes condense and become visible. The nuclear membrane also disappears, and the chromosomes are free in the cytoplasm.

Question 5

In which of the stages of mitosis cell division does the nuclear membrane reap sear?

  1. anaphase.
  2. Prophase.
  3. Metaphase.
  4. Telophase

Answer

Telophase

Explanation

During telophase, the chromosomes decondensed, and the nuclear membrane reforms. The cytoplasm also divides, forming two daughter cells.

Question 6

Four daughter cells are obtained from

  1. Mitosis.
  2. Meiosis.
  3. Amitosis
  4. None of them

Answer

Meiosis

Explanation

Mitosis and amitosis both produce two daughter cells, while meiosis produces four daughter cells.

Question 7

Half of the chromosomes move towards the two poles of bame in mitosis.

  1. Metaphase.
  2. Telophase
  3. Anaphase
  4. Prophase

Answer

Anaphase

Explanation

During anaphase, the sister chromatids of each chromosome separate and move towards the opposite poles of the cell. This is the stage where half of the chromosomes move towards the two poles of the cell.

Question 8

Centromere is present at the centre of chromosomes in

  1. Metacentric
  2. Acrocentric
  3. Telocentric
  4. Sub-metacentric

Answer

Metacentric

Explanation

In metacentric chromosomes, the centromere is located near the center of the chromosome. This means that the two arms of the chromosome are of equal length.

Question 9

The chromosome-bearing centromere at the terminal end is called

  1. Sub-metacentric chromosome.
  2. Telocentric chromosome.
  3. Metacentric chromosome.
  4. Acrocentric chromosome

Answer

Telocentric chromosome

Explanation

A telocentric chromosome is a type of chromosome that has its centromere located at the very end of the chromosome. This means that the chromosome has only one arm. Telocentric chromosomes are found in some animals, plants, and fungi.

Question 10

Gene is part of

  1. DNA
  2. RNA
  3. a & b both
  4. None of them

Answer

DNA and RNA

Explanation

A gene is a unit of heredity that is made up of DNA. DNA is a molecule that contains the instructions for building proteins. Proteins are the building blocks of cells, and they carry out many important functions in the body.

RNA is a molecule that is similar to DNA, but it is single-stranded instead of double-stranded. RNA is used to make proteins from the instructions in DNA.

Question 11

Autosome number in the human body is

  1. 45
  2. 40
  3. 44
  4. 42

Answer

44

Explanation

Autosomes are chromosomes that are not sex chromosomes. In humans, there are 22 pairs of autosomes, for a total of 44 autosomes. The sex chromosomes are the X and Y chromosomes. Females have two X chromosomes, while males have one X chromosome and one Y chromosome.

Question 12

In chromosome satellite present at

  1. Chromatid
  2. Primary constriction
  3. Secondary constriction
  4. Centromere

Answer

Secondary constriction

Explanation

A satellite is a small, spherical body that is attached to the short arm of some chromosomes. It is thought to be made up of repetitive DNA sequences. Satellites are often associated with nucleolar organizer regions (NORs), which are regions of the chromosome that contain genes that are involved in the production of ribosomes.

Question 13

Which amino acid is present in the acidic protein of the chromosome?

  1. Tryptophan.
  2. Leucine.
  3. Valine
  4. Lysine

Answer

Lysine

Explanation

Lysine is an acidic amino acid that is found in chromosomes. It has a positive charge at physiological pH, which helps to neutralize the negative charge of the DNA backbone.

Question 14

Which one is equational division?

  1. Cytokinesis
  2. Amitosis
  3. Mitosis
  4. Meiosis

Answer

Mitosis

Explanation

Mitosis is a type of cell division that occurs in somatic cells. Somatic cells are all the cells in the body except for gametes (sex cells). During mitosis, the DNA in the cell is replicated, and the cell then divides into two daughter cells that are genetically identical to the parent cell.

Question 15

In which type of reproduction, mitosis & meiosis both are involved

  1. Sexual reproduction
  2. Vegetative propagation
  3. Asexual reproduction
  4. None of them

Answer

Sexual reproduction

Explanation

Sexual reproduction is a type of reproduction that involves the fusion of two gametes, one from each parent. The gametes are produced by meiosis, which is a type of cell division that reduces the number of chromosomes by half. The fusion of the gametes then restores the full number of chromosomes in the zygote, which is the cell that develops into the new organism.

Question 16

Fragmentation found in

  1. Hydra
  2. Planaria
  3. Amoeba
  4. Spirogyra

Answer

Spirogyra

Explanation

Fragmentation is a type of asexual reproduction that occurs when a parent organism breaks up into smaller pieces, each of which can grow into a new organism.

Question 17

Grafting is found in

  1. Ginger
  2. Potato
  3. Guava
  4. Sesbania

Answer

Guava

Explanation

Grafting is a technique used to join two different plants together so that they can grow as one plant. The plant that provides the roots is called the stock, and the plant that provides the top growth is called the scion.

Question 18

Every part of Calyx called as

  1. Sepal
  2. Petal
  3. Stamen
  4. Carpel

Answer

Sepal

Explanation

A calyx is the outermost whorl of floral parts in a flower. It is composed of sepals, which are leaf-like structures that protect the flower bud before it opens. Sepals are usually green, but they can also be brightly coloured.

Question 19

Self-pollination found in

  1. Mirabilis
  2. Borassus
  3. Cucurbita
  4. Solanum

Answer

Mirabilis

Explanation

Self-pollination is the pollination of a flower by its own pollen. It can occur in plants that have both male and female reproductive organs in the same flower (perfect flowers) or in plants that have separate male and female flowers (imperfect flowers).

Question 20

Anemophily found in

  1. Hydrilla
  2. Maize
  3. Vallisneria
  4. Mango

Answer

Maize

Explanation

Anemophily is a type of pollination that is carried out by wind. The pollen grains of anemophilous plants are typically small and lightweight, and they have smooth surfaces that allow them to be easily carried by the wind.

Question 21

Ornithophily found in

  1. Shimul
  2. Sunflower
  3. Mango
  4. Paddy

Answer

Shimul

Question 22

In the case of humans after 10 months to 13 years of age is called

  1. Infancy
  2. Adolesce
  3. Childhood
  4. Senescence

Answer

Childhood

Explanation

Childhood is the developmental stage between infancy and adolescence, typically from 1 to 12 years of age. It is a time of rapid physical, emotional, and cognitive development. Children in this stage are learning about the world around them and developing their own unique personalities.

Question 23

Sex determinant chromosome of females is

  1. XX
  2. XO
  3. YY
  4. XY

Answer

XX

Explanation

Humans have 23 pairs of chromosomes, of which one pair is the sex chromosome. The sex chromosomes are the X chromosome and the Y chromosome. Females have two X chromosomes, while males have one X chromosome and one Y chromosome.

Question 24

The number of sex chromosomes in humans is

  1. 4
  2. 2
  3. 46
  4. 23 pairs

Answer

2

Explanation

Humans have 23 pairs of chromosomes, of which one pair is the sex chromosome. The sex chromosomes are the X chromosome and the Y chromosome. Females have two X chromosomes, while males have one X chromosome and one Y chromosome.

Question 25

Secondary sex characters are established in

  1. Late adulthood
  2. Adulthood
  3. Adolescence
  4. Childhood

Answer

Adolescence

Explanation

Secondary sex characteristics are physical traits that are not directly involved in reproduction but are associated with a particular sex. In humans, these characteristics typically develop during puberty, which is the period of transition from childhood to adulthood.

Fill in the Blanks

Question 1

In the ____ phase of the cell cycle DNA is synthesized.

Answer

S phase

Question 2

Uncontrolled cell division takes place resulting in the formation of ____.

Answer

tumours

Question 3

Shimul is ____ pollinated flower.

Answer

Cross

Question 4

The male gamete and female gamete unite to form ____.

Answer

zygote

Question 5

Secondary sex characters are established in ____.

Answer

adolescence

Mention True or False

Question 1

During gastrulation, cells enlarge and form tissues by elongation. 

Answer

True

Question 2

In fern, alternation of generation is found.

Answer

True

Question 3

By fertilization, the ovule converts into a seed.

Answer

True

Question 4

The paired homologous chromosomes together are called synapsis.

Answer

False

Question 5

Pyrimidines are two types-cytosine and guanine.

Answer

False

Column Matching :

Question 

Left Column Right Column
A. Chromatid (i) Chromonema
B. Chromomere (ii) ATP generation
C. Mitochondria (iii) Uracil
D. RNA (iv) Chromosome

Answer

Left Column Right Column
A. Chromatid (iv) Chromosome
B. Chromomere (i) Chromonema
C. Mitochondria (ii) ATP generation
D. RNA (iii) Uracil

Question 

Left Column Right Column
A. Cytokinin (i) Plantlet
B. Embroid (ii) Grafting
C. Scion (iii) Cutting
D. Citrus (iv) Tissue culture

Answer

Left Column Right Column
Cytokinin (iv) Tissue culture
Embroid (i) Plantlet
Scion (ii) Grafting
Citrus (iii) Cutting

Very Short Answer (VSA) Type Questions

Question 1

Mention the site of G0.

Answer

G0 is a resting stage of the cell cycle. It is found in cells that have stopped dividing, such as muscle cells and nerve cells.

Question 2

What is the full form of DNA?

Answer

DNA stands for deoxyribonucleic acid.

Question 3

Write full form of RNA?

Answer

RNA stands for ribonucleic acid.

Question 4

Mention the location of the gene.

Answer

Genes are located on chromosomes.

Question 5

What is the number of chromosomes in the human body?

Answer

Humans have 46 chromosomes in their body cells. 23 of these chromosomes come from the mother and 23 come from the father.

Question 6

Define sat-chromosome.

Answer

A sat-chromosome is a chromosome that has a small satellite attached to it. Satellites are small, round, extra pieces of DNA that are found on some chromosomes.

Question 7

What are the nitrogenous bases of DNA?

Answer

The nitrogenous bases of DNA are adenine (A), guanine (G), cytosine (C), and thymine (T).

Question 8

Which cell organelle is involved in the formation of bame?

Answer

The cell organelle involved in the formation of bame is the ribosome.

Question 9

Where does amitosis cell division occur?

Answer

Amitosis occurs in cells that are not dividing very often, such as muscle cells and nerve cells.

Question 10

What is the unit of asexual reproduction?

Answer

The unit of asexual reproduction is the cell.

Question 11

Mention the threat of sexual reproduction.

Answer

The threat of sexual reproduction is that it can lead to the production of offspring with genetic defects.

Question 12

What is a haploid cell?

Answer

A haploid cell is a cell that has only one set of chromosomes.

Question 13

Define diploid cell.

Answer

A diploid cell is a cell that has two sets of chromosomes.

Question 14

What is chromatin reticulum?

Answer

Chromatin reticulum is a network of DNA and protein that is found in the nucleus of cells.

Question 15

What is a telocentric chromosome?

Answer

A telocentric chromosome is a chromosome that has a centromere located at the end of the chromosome.

Question 16

What do you mean by acrocentric chromosome? 

Answer

An acrocentric chromosome is a chromosome that has a centromere located near one end of the chromosome.

Question 17

Define metacentric chromosome.

Answer

A metacentric chromosome is a chromosome that has a centromere located in the middle of the chromosome.

Question 18

What is sat-chromosome?

Answer

A sat-chromosome is a chromosome that has a small satellite attached to it.

Question 19

Write the pyrimidines of nucleic acid. 

Answer

The pyrimidines of nucleic acid are cytosine (C), thymine (T), and uracil (U).

Question 20

What is the cell cycle?

Answer

The cell cycle is the series of events that a cell goes through from its formation to its division. The cell cycle consists of two main phases: interphase and mitosis.

Question 21

Name the organisms where asexual reproduction is found. 

Answer

Asexual reproduction is found in many different organisms, including bacteria, fungi, plants, and animals.

Question 22

What is the flower? 

Answer

A flower is the reproductive organ of a flowering plant. It is made up of four main parts: the sepals, petals, stamens, and pistils.

Question 23

Define gamosepalous calyx.

Answer

A gamosepalous calyx is a calyx that is fused together. This means that the sepals are not separate from each other.

Question 24

What are stamens?

Answer

Stamens are the male reproductive organs of a flower. They are made up of a filament and an anther. The anther is where the pollen is produced.

Question 25

Give the example of a regular flower.

Answer

A regular flower is a flower that has all of its parts arranged in a symmetrical pattern. This means that the petals are all the same size and shape, and the sepals are all the same size and shape.

Question 26

What is an irregular flower?

Answer

An irregular flower is a flower that does not have all of its parts arranged in a symmetrical pattern.

Question 27

Give an example of water pollinated plant.

Answer

An example of a water-pollinated plant is the water lily.

Question 28

Write an example of cross-pollination.

Answer

Apples, grasses, maple trees.

Question 29

Give an example of a wind-pollinated plant. 

Answer

An example of a wind-pollinated plant is the corn plant.

Question 30

Name one bird-pollinated plant.

Answer

One bird-pollinated plant is the hummingbird sage.

Short Answer (SA) Type Questions

Question 1

What is a chromosome?

Answer

A chromosome is a thread-like structure located inside the nucleus of animal and plant cells. Each chromosome is made up of protein and a single molecule of deoxyribonucleic acid (DNA). DNA contains the genetic instructions that make each type of living creature unique.

Question 2

What is a gene?

Answer

A gene is a unit of heredity that is located on a chromosome. Genes control the development and function of an organism.

Question 3

Mention the two characteristics of the gene.

Answer

The two characteristics of a gene are:

  • It is a unit of heredity.
  • It is located on a chromosome.

Question 4

What is autosome?

Answer

An autosome is any chromosome that is not a sex chromosome. In humans, there are 22 pairs of autosomes, for a total of 44 chromosomes. The remaining pair of chromosomes are the sex chromosomes, which can be either XX (female) or XY (male).

Question 5

What is a sex chromosome? 

Answer

A sex chromosome is a chromosome that determines the sex of an individual. In humans and most other mammals, there are two sex chromosomes: X and Y. Females have two X chromosomes, while males have one X chromosome and one Y chromosome.

Question 6

What is a centromere?

Answer

The centromere is a region of a chromosome that is involved in cell division. It is the point where the two chromatids of a chromosome are attached.

Question 7

What is chromomere?

Answer

A chromomere is a bead-like structure that is found along the length of a chromosome. Chromomeres are visible during mitosis and meiosis.

Question 8

Give two differences between DNA & RNA

Answer

The two differences between DNA and RNA are:

  • DNA is a double-stranded molecule, while RNA is a single-stranded molecule.
  • DNA contains the sugar deoxyribose, while RNA contains the sugar ribose.

Question 9

What is the role of the centrosome in cell division? 

Answer

The centrosome is a structure that is found in the cytoplasm of cells. It is involved in cell division. The centrosome produces the spindle fibres that are used to separate the chromosomes during mitosis and meiosis.

Question 10

What is amitosis?

Answer

Amitosis is a type of cell division that does not involve the formation of spindle fibres. Amitosis is a common type of cell division in unicellular organisms, but it is also found in some multicellular organisms.

Question 11

What is mitosis?

Answer

Mitosis is a type of cell division that produces two identical daughter cells. Mitosis is the process by which cells divide to grow and repair themselves.

Question 12

Give two significance of mitosis. 

Answer

The two significances of mitosis are:

  • It is the process by which cells divide to grow and repair themselves.
  • It is the process by which cells divide to produce gametes.

Question 13

What is meiosis?

Answer

Meiosis is a type of cell division that produces four daughter cells with half the number of chromosomes as the parent cell. Meiosis is the process by which gametes are produced.

Question 14

Give two significance of meiosis

Answer

The two significances of meiosis are:

  • It is the process by which gametes are produced.
  • It is the process by which genetic variation is introduced into a population.

Question 15

What is the cell cycle?

Answer

The cell cycle is the series of events that a cell goes through from its formation to its division. The cell cycle consists of two main phases: interphase and mitosis.

Question 16

Give two characteristics of metaphase

Answer

The two characteristics of metaphase are:

  • The chromosomes are aligned at the equator of the cell.
  • The spindle fibres are attached to the centromeres of the chromosomes.

Question 17

State two features of anaphase

Answer

The two features of anaphase are:

  • The chromatids of each chromosome separate.
  • The chromosomes move to opposite poles of the cell.

Question 18

What is cytokinesis?

Answer

Cytokinesis is the process by which the cytoplasm of a cell is divided into two daughter cells. Cytokinesis occurs after mitosis.

Question 19

What is bivalent?

Answer

A bivalent is a pair of homologous chromosomes that are joined together during meiosis. Homologous chromosomes are chromosomes that carry the same genes, but they may have different alleles for those genes. Bivalents are formed when homologous chromosomes pair up during prophase I of meiosis. This pairing process is called synapsis.

Question 20

Define Euchromatin

Answer

Euchromatin is a type of chromatin that is loosely packed and active in transcription. Euchromatin makes up most of the DNA in a cell.

Question 21

What is heterochromatin?

Answer

Heterochromatin is a type of chromatin that is tightly packed and inactive in transcription. Heterochromatin is found in the centromeres and telomeres of chromosomes.

Question 22

Give two differences between mitosis & meiosis

Answer

The two differences between mitosis and meiosis are:

  • Mitosis produces two identical daughter cells, while meiosis produces four daughter cells with half the number of chromosomes as the parent cell.
  • Mitosis is a continuous process, while meiosis is a discontinuous process.

Question 23

What is asexual reproduction?

Answer

Asexual reproduction is a type of reproduction where a new organism is produced from a single parent. Asexual reproduction is common in bacteria, fungi, and plants.

Question 24

What is sexual reproduction?

Answer

Sexual reproduction is a type of reproduction where a new organism is produced from two parents.

Question 25

What is cutting?

Answer

A cutting is a piece of plant tissue that is used to propagate a new plant. Cuttings are typically taken from the stems or leaves of a plant.

Question 26

What do you mean by grafting?

Answer

Grafting is a technique used to join two different plants together so that they grow as one. The scion, which is the desired part of the plant, is grafted onto the rootstock, which provides support for the scion.

Question 27

Define micropropagation

Answer

Micropropagation, also known as plant tissue culture, is a technique used to rapidly produce large numbers of plants from small pieces of plant tissue. This technique is widely used in commercial horticulture to propagate plants that are difficult to propagate by traditional methods, such as seeds or cuttings.

Question 28

Define alternation of generation

Answer

Alternation of generations is a life cycle that is found in some plants and algae. In the alternation of generations, the organism alternates between two different phases: a haploid phase and a diploid phase.

Question 29

What is pollination?

Answer

Pollination is the transfer of pollen from the male part of a flower to the female part of a flower. Pollination is necessary for sexual reproduction in flowering plants.

Question 30

What is self-pollination?

Answer

Self-pollination is the transfer of pollen from the male part of a flower (the anther) to the female part of the same flower (the stigma). This can happen directly, within the same flower, or indirectly, when pollen is transferred from one flower to another flower on the same plant.

Question 31

What is cross-pollination?

Answer

Cross-pollination is the transfer of pollen from the male part of one flower (the anther) to the female part of a different flower (the stigma). This can happen between flowers on the same plant, or between flowers on different plants of the same species. Cross-pollination is the most common method of reproduction in flowering plants.

Question 32

What is the complete flower?

Answer

A complete flower is a flower that has all four of the following parts:

  • Sepals: The sepals are the outermost parts of a flower. They are usually green and leaf-like, and they protect the bud of the flower before it blooms.
  • Petals: The petals are the brightly coloured parts of a flower. They attract pollinators, such as insects and birds, which help to transfer pollen from one flower to another.
  • Stamens: The stamens are the male reproductive parts of a flower. They are composed of an anther, which produces pollen, and a filament, which supports the anther.
  • Pistil: The pistil is the female reproductive part of a flower. It is composed of a stigma, which receives pollen, a style, which supports the stigma, and an ovary, which contains the ovules (eggs).

Question 33

Define growth.

Answer

Growth is the increase in the size of an organism. Growth can be measured by the increase in length, width, or weight of an organism.

Question 34

What is development?

Answer

Development is the process of growth and change that an organism undergoes over time. It is a complex process that involves both physical and behavioural changes.

Long Answer (LA) Type Questions

Question 1

What is a chromosome? What is the inter-relationship among chromosomes, DNA and gene?

Answer

A chromosome is a thread-like structure in cells that carries genetic information in the form of DNA.

DNA is the molecule inside chromosomes that encodes hereditary data. Genes are specific segments of DNA that determine traits. Chromosomes contain DNA, and DNA holds genes, forming an interdependent relationship crucial for heredity and the functioning of living organisms.

Question 2

State the types of chromosomes. What is the difference between a centrosome and a centromere?

Answer

The types of chromosomes are autosomes and sex chromosomes.

Centrosome Centromere
Found outside the cell nucleus. Located on the centromere region of a chromosome.
Composed of two centrioles. Composed of a specialized DNA sequence.
Plays a role in cell division and organizing spindle fibers. Ensures proper separation of chromatids during cell division.

Question 3

Describe the structure of chromosomes with proper diagrammatic representation

Answer

Structure of Chromosome

Structure of chromosomes

  1. Telomere: Protective DNA caps at chromosome ends.
  2. Chromosome: Thread-like structure with DNA and histone proteins.
  3. Sister Chromatid: Identical copies held by a centromere during cell division.

Question 4

State the chemical components of the chromosome

Answer

The chemical components of a chromosome include:

  1. Deoxyribonucleic acid (DNA): The fundamental genetic material, composed of nucleotides carrying genetic information.
  2. Histone Proteins: Wrap and condense DNA, forming chromatin, and helping regulate gene expression.
  3. Telomeres: Specific DNA sequences and associated proteins at the ends of chromosomes, protecting genetic material during cell division and ageing.
  4. Centromeres: Specialized DNA regions that facilitate the attachment of spindle fibres during cell division.

Question 5

What do you mean by heterochromatin and euchromatin? Mention their individual characteristics

Answer

Heterochromatin and euchromatin are two types of chromatin, which is the condensed form of DNA in chromosomes.

Heterochromatin:

  • Characteristics: Dense, tightly packed DNA.
  • Function: Mostly inactive, silencing genes.
  • Location: Usually found near the centre of the nucleus.

Euchromatin:

  • Characteristics: Loosely packed DNA.
  • Function: Active, allowing gene expression.
  • Location: Distributed throughout the nucleus.

Question 6

State the structure of DNA

Answer

DNA-Structure

The structure of DNA is a double helix. It consists of two long strands of nucleotides, each with a sugar-phosphate backbone and nitrogenous bases (adenine, thymine, cytosine, and guanine) pairing in the centre with specific hydrogen bonds (A-T and C-G).

Question 7

What is RNA? Mention the difference between DNA and RNA

Answer

RNA stands for Ribonucleic Acid. It is a single-stranded molecule that plays a crucial role in various cellular processes, including protein synthesis.

Aspect DNA RNA
Structure Double stranded Single stranded
Bases A, T, C, G A, U, C, G
Function Stores genetic information Involved in protein synthesis

Question 8

Mention the role of nucleus, centrosome and mitochondria in cell division.

Answer

  1. Nucleus:
    • Holds the cell’s genetic material (DNA) in the form of chromosomes.
    • Regulates cell division by coordinating DNA replication and distributing chromosomes to daughter cells during mitosis and meiosis.
  2. Centrosome:
    • Organizes microtubules, forming the mitotic spindle necessary for cell division.
    • Helps separate duplicated chromosomes by pulling them apart to opposite poles during mitosis and meiosis.
  3. Mitochondria:
    • Provides energy (in the form of ATP) required for various cellular processes, including cell division.
    • Supports the synthesis of materials needed for cell division, ensuring the proper functioning of the dividing cell.

Question 9

What is cell division? What is the significance of cell division?

Answer

Cell division is the process by which a single cell divides to form two or more daughter cells.

Significance:

  • Allows growth, development, and tissue repair in organisms.
  • Enables asexual and sexual reproduction.
  • Introduces genetic diversity for evolution and adaptability.

Question 10

What is the cell cycle? Briefly describe the phases of the cell cycle.

Answer

The cell cycle is the sequence of events that a cell undergoes as it divides and duplicates its contents to produce two daughter cells.

Phases of the cell cycle:

  1. Interphase: The cell prepares for division, grows, and duplicates its DNA.
  2. Mitosis: The cell’s nucleus divides into two identical nuclei, each containing a complete set of DNA.
  3. Cytokinesis: The cell’s cytoplasm divides, and two daughter cells are formed.

Question 11

What is the significance of the cell cycle? Why mitosis is called equational division?

Answer

The significance of the cell cycle lies in its ability to allow cells to grow, reproduce, and replace damaged or dead cells, enabling the development, maintenance, and regeneration of living organisms.

Mitosis is called “equational division” because it results in the production of two daughter cells with the same number of chromosomes as the parent cell. It ensures genetic stability and the identical distribution of genetic material between daughter cells.

Question 12

Briefly describe the metaphase and anaphase of mitosis with correct diagrammatic representation.

Answer

MetaPhase e1690568069949

Metaphase of Mitosis:

  1. Chromosomes align at the cell’s equatorial plane (metaphase plate).
  2. Spindle fibres from centrosomes attach to the centromeres of sister chromatids.
  3. Chromosomes are maximally condensed and visible under the microscope.

Anaphase

Anaphase of Mitosis:

  1. Sister chromatids separate and are pulled to opposite poles of the cell.
  2. Spindle fibres shorten, exerting tension to move the chromatids.
  3. The cell elongates as chromatids move towards the poles, ensuring each daughter cell receives a complete set of chromosomes.

Question 13

What is meiosis? Briefly explain the features of meiosis-I

Answer

Meiosis is a type of cell division that occurs in sexually reproducing organisms to produce gametes (sperm and eggs) with half the number of chromosomes found in body cells.

Features of Meiosis-I:

  1. Homologous Chromosome Pairing: Chromosomes in the cell align and pair with their homologous partner (one from each parent).
  2. Crossing Over: Genetic exchange occurs between homologous chromosomes, promoting genetic diversity.
  3. Reductional Division: The homologous pairs separate, reducing the chromosome number by half in each daughter cell.
  4. Independent Assortment: The assortment of homologous chromosomes is random, leading to further genetic variation.

Question 14

State the difference between mitosis of plant cells and animal cells. What is prophase?

Answer

Aspect Plant Cell Animal Cell
Cell Wall Presence of rigid cell wall Absence of cell wall
Centrioles Lack centrioles Presence of centrioles
Cytokinesis Cell plate formation Cleavage furrow formation

Prophase is the first stage of mitosis or meiosis, where chromosomes condense, the nuclear envelope breaks down, and the mitotic spindle starts to form.

Question 15

What are the features of meiosis-II? What is sister chromatid?

Answer

Features of Meiosis-II:

  1. Sister chromatids from each chromosome separate and move to opposite poles of the cell.
  2. Each daughter cell receives a complete set of chromosomes, but they are now haploid (half the number of chromosomes as the parent cell).
  3. No further replication of DNA occurs before meiosis II.

Sister chromatids are two identical copies of a single chromosome held together at the centromere.

Question 16

What is crossing over? Mention the process of crossing over

Answer

crossing over

Crossing over is a process that occurs during meiosis, where specific segments of genetic material are exchanged between homologous chromosomes.

Process of Crossing Over:

  1. Homologous chromosomes pair up during meiosis.
  2. Sections of non-sister chromatids break and exchange genetic material.
  3. This creates new genetic combinations in the chromatids.
  4. Crossing over increases genetic diversity, leading to unique traits in offspring.

Question 17

Mention the significance of meiosis. State the difference between mitosis and meiosis.

Answer

Significance of meiosis

  1. Genetic Diversity: Meiosis creates genetically diverse offspring through crossing over and independent assortment.
  2. Maintains Chromosome Number: Halves the chromosome number in gametes to restore the diploid number after fertilization.
Aspect Mitosis Meiosis
Purpose Cell growth, repair, and asexual reproduction. Producing gametes and enabling sexual reproduction.
Number of Divisions One division (mitosis) Two divisions (meiosis I and meiosis II)
Chromosome Number Maintains chromosome number (diploid). Halves chromosome number (haploid gametes).

Question 18

What are the importance of reproduction? Define reproduction.

Answer

Importance of Reproduction:

  1. Reproduction ensures the survival and continuity of species over generations.
  2. Sexual reproduction introduces genetic variation, enhancing adaptability to changing environments.
  3. Reproduction allows the growth and development of new individuals, maintaining the population size of organisms.

Reproduction is the biological process by which living organisms produce offspring of the same species.

Question 19

Describe the different types of asexual reproduction with proper examples.

Answer

Types of asexual reproduction:

  1. Binary Fission: The parent cell divides into two genetically identical daughter cells. Example: Bacteria like Escherichia coli.
  2. Budding: New individual develops as an outgrowth (bud) from the parent and separates. Example: Yeast and Hydra.
  3. Fragmentation: The parent organism breaks into fragments, and each fragment grows into a new individual. Example: Starfish and flatworms.
  4. Vegetative Propagation: New plants develop from vegetative parts (e.g., roots, stems, or leaves) of the parent plant. Example: Strawberry runners and potato tubers.
  5. Parthenogenesis: Offspring develop from unfertilized eggs, without male involvement. Example: Some insects like aphids and bees.

Question 20

What is vegetative propagation? Mention the vegetative propagation by roots and stems.

Answer

Vegetative Propagation: A form of asexual reproduction in plants where new individuals develop from vegetative parts (not seeds).

Vegetative Propagation by Roots:

  1. Adventitious roots grow from stems or nodes, producing new plants.
  2. Examples: Sweet potato and Dahlia.

Vegetative Propagation by Stems:

  1. Nodes or buds on stems develop into new plants.
  2. Examples: Potato and Mint.

Question 21

Describe the different methods of artificial vegetative propagation.

Answer

Different Methods of Artificial Vegetative Propagation:

  1. Cuttings: Plant parts like stems or leaves are cut and placed in suitable conditions to develop into new plants.
  2. Grafting: Joining a stem (scion) of one plant to the root system (rootstock) of another to grow as a single plant.
  3. Layering: Burying a branch of the parent plant in the soil until it develops roots and then separating it as an independent plant.
  4. Tissue Culture: Growing plant cells or tissues in a laboratory to produce new plants under sterile conditions.

Question 22

What is an alternation of generation? Explain the alternation of generation in fern.

Answer

Alternation of Generations:

A life cycle where plants alternate between haploid (n) and diploid (2n) generations, involving both gametophyte and sporophyte stages.

Alternation of generation

Alternation of Generation in Fern:

  1. Sporophyte Stage (2n): The dominant stage. Sporophytes produce spores through meiosis in structures called sporangia.
  2. Spore Formation: Spores are released and develop into a gametophyte.
  3. Gametophyte Stage (n): The gametophyte produces gametes (sperm and eggs) through mitosis.
  4. Fertilization: Sperm fertilizes an egg, forming a zygote.
  5. Embryonic Sporophyte: The zygote develops into a new sporophyte, completing the cycle.

Question 23

Describe the different parts of the flower.

Answer

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The different parts of the flower

  1. Petals: Colorful and attractive outer parts of the flower.
  2. Sepals: Green leaf-like structures at the base of the flower.
  3. Stamen: Male reproductive part, includes filament and anther.
  4. Pistil (or Carpel): Female reproductive part, consisting of stigma, style, and ovary.
  5. Ovules: Eggs found inside the ovary, which develop into seeds when fertilized.

Question 24

What is fertilization? Describe the process of fertilization in plants.

Answer

Fertilization is the process of fusion between male and female gametes, resulting in the formation of a zygote, which develops into a new individual.

Process of Fertilization in Plants:

  1. Pollination: Pollen grains (male gametes) from the anther land on the stigma (female part).
  2. Germination: Pollen tube grows from the stigma to the ovary.
  3. Fusion: Sperm (male gamete) travels through the pollen tube and fuses with the egg (female gamete) inside the ovule.
  4. Zygote Formation: The fertilized egg becomes a zygote, which develops into an embryo.
  5. Seed Formation: The ovule develops into a seed, containing the embryo and stored food.
  6. Fruit Formation: The ovary enlarges and becomes a fruit, protecting the seeds.

Question 25

What is growth? Briefly describe the different phases of human development. 

Answer

Growth:

The process of physical, physiological, and behavioural changes that result in an increase in the size, complexity, and capability of an organism.

Phases of Human Development:

  1. Infancy: It extends from birth to 10 months of age. At birth, the head is about one-fourth of the whole body. After birth, the arms grow faster than the legs. The infant is a vibrant and seemingly unlimited source of energy.
  2. Childhood: It extends from 10 months to about 13 years of age. The legs attain their proportionate sUe only after 10 years. The growth rate increases gradually.
  3. Adolescence: It extends from 13 years to 18 years of age. There is enhanced activity of growth hormones. The growth rate is high and attains a maximum. Due to the increase in sex hormones secondary sex characters are established in males and females.
  4. Adulthood: It extends from 18 years to 25 years of age. After the age of 18 years, the growth rate gets reduced and stops altogether after the age of 22 – 22 years. Secretion of sex hormones is diminished and the function of STH is almost closed.
  5. Senescence or late adulthood: It extends from 25 years of age onwards. After 25 years of age, many organs show a gradual decline in their functional activities. Many organs may even regress in size. As the organism grows older the power of metabolism gradually declines.

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