NIOS Class 10 Science Worksheet 21 Questions Answers – Building Blocks of Life Cell and Tissues

This Worksheet 21 contains questions based on Chapter 21Building Blocks of Life Cell and Tissues complete answers.

 

 

This post explains the answers of questions given in the worksheet including explanation, diagrams. These solutions will help you complete your assignments and TMA also.

 

Building Blocks of Life Cell and Tissues Worksheet 21 Solution

 

Q1. “Cells are the basic structural units of living organisms”. Justify the statement?

Answer

The statement” Cells are the basic structural units of living organisms “is correct
because all living things are made up cells.

 We know a house is made of bricks, the body of plants and animals of cells. Every organism starts its life as a single cell which divides many times to form more cells, same type of cells joins together to form tissues and tissues form organs and organs combined to form a whole body.

If cell get damaged or worn out, new cells are formed to replace them so cells are
necessary to build and maintain the body.

 

Q2. Draw a typical cell. Label important organelles.

Answer

 

 

Q3.Differentiate between Prokaryotic and Eukaryotic cell.

Answer

Feature	Prokaryotic cell	Eukaryotic cell
Nucleus	Well defined nucleus is absent	Well defined nucleus is present
Nuclear membrane	Absent	Present
Genetic material	DNA lies in cytoplasm	DNA is found in nucleus
Cell organelles	Membrane bound cell organelles are absent	Membrane bound cell organelles are present
Example	Bacteria, blue-green algae	Plants, animals, fungi

 

 

Q4.Give on function each of the following organelles: Mitochondria, Endoplasmic reticulum, Ribosomes, Nucleus, Golgi bodies, Lysosomes.

Answer

The functions of the given cell organelles are as follows :

 

1. Mitochondria: – They release energy during respiration and are called powerhouse of the cell.

 

2. Endoplasmic reticulum: – It helps in the transport of proteins and fats inside the cell.

 

3. Ribosomes: – They are the sites of protein synthesis in the cell.

 

4. Nucleus: – It controls all activities of the cell and contains genetic material like DNA.

 

5. Golgi Bodies: -They help in the secretion and storage of substances like enzymes and hormones.

 

6. Lysosomes: – They digest worn out cells and are called suicide bags of the cell

 

Q5. Name three kinds of permanent tissues found in plants? Write one function of each?

Answer

The three types of permanent tissues in plats are

1. Protective tissues: – This tissue is made of cells with thick walls and occurs on the surface of leaves, stem and roots. It protects the plant from injury, drying and harmful substances. Example – epidermis

2. Supporting tissues: – These tissues provide support to various parts of plant. It gives support and strength to different parts of plant. Example – tissues in leaf stalks and potatoes.

3. Conducting tissue: – It is called vascular tissue and transports water, minerals and food in the plants. They are xylem and phloem.

Q6.State the stages and significance of meiosis?

Answer

Stages of Meiosis

Meiosistakes place in two main phases:

   1. Phase I (first meiotic division)

    i.      Chromatin fibres condense to form chromosomes.

    ii.    Homologous chromosomes pair up.

   iii.   Nuclear membrane disappears.

   iv.   Homologous chromosomes separate and move apart.

    v.   Cytoplasm divides to form two cells and each have half the number of chromosomes.

   

   2. Phase II (second meiotic division)

    i.    It is similar to mitosis.

    ii.  Centrosome divides and chromatids separate.

   iii. Cytoplasm divides again.

   iv. Four cells are formed and each cell half the number of chromosomes of the parent cell.

 

Significance of Meiosis

    1. It halves the number of chromosomes in sex cells.

    2. It helps in maintaining the constant number of    chromosomes in a species after fertilization.

    3. It produces new combination of genes which leads to variation.

   4. It is essential for sexual reproduction.

 

Q7. With the help of diagram of animal and plant cells. State the points of difference between them?

Answer

 

Feature	Plant cell	Animal cell
Size and shape	Larger and rectangular	Smaller and oval
Cell wall	Present	Absent
Vacuole	One large vacuole	Small or absent
Plastids	Present	Absent
Golgi bodies	Absent	Present
centrosome	Absent	Present
Reserve food	Stored as starch	Stored as glycogen

 

 

Q8. Draw a sketch of the human nerve cell. What function do nerve cells perfume?

Answer

 

Functions of Nerve cells

Nerve cells carry messages (nerve impulses) from on part of the body to another. They help in thinking, feeling, movement and coordination of body activities.

 

Q9. Mention the different types of connective tissues? Give one function of each?

Answer

The different types of connective tissues and their functions are following

    1. Fibrous tissue: – Tendon, ligament and areolar tissues are examples of fibrous tissue. It connects different parts. Tendon connects muscles to bone and ligament connects bone to bone.

   2. Adipose tissue: – It stores fat and acts as a cushion to protect organs.

   3. Cartilage: – It provides support and flexibility to body parts like nose, ears and joints.

   4. Bone: – It gives shape and strength to the body and helps in movement.

   5. Blood: – It transports gases and nutrients to different parts of the body.

 

   6. Lymph: – It helps in protection against disease causing germs and in transport of
substances.

 

Q10.Wirte a note on “Stem cell technology”? give its two uses in disease control.

Answer

Stem Cell Technology

Stem cells are undifferentiated (unspecialised)cells which can divide by mitosis and
change into specialised cells like blood cells, nerve cells or muscles cells. They
can also make more stem cells. These cells are obtained from (i) embryo (ii) Umbilical cord (iii) bone marrow

 Two uses of Stem Cell Technology in Disease Control

   1. To replace damaged tissues- Stem cells can be used   to repair or replace tissues damaged due to diseases or injuries.

   2. Bone marrow transplant to treat blood cancer -Stem cell therapy is used in bone marrow transplant for treating leukemia.

 

 Related Topics

1). NIOS Class 10 Science Worksheets Solutions Set 1