WBBSE Class 8 Science Solutions Chapter 6 The Structure of Living Organisms

Detailed explanations in West Bengal Board Class 8 Science Book Solutions Chapter 6 The Structure of Living Organisms offer valuable context and analysis.

WBBSE Class 8 Science Chapter 6 Question Answer – The Structure of Living Organisms

Complete the table : (See Text Book Page 178)

Name of cell	Shape of cell
1. Erythrocyte	Red Blood Corpuscles are rounded and flatened on both sides. They look like a disc.
2. Leucocyte	Leucocyte cells change their shape very often.
3. Muscle cell	Muscle cells are spindle shaped, both ends are tapering.
4. Nerve cell	The nerve cell is comparatively longer than other cells. The cell body is star-shaped or rounded and branches of different shapes remain connected with it.
5. Apical cell of root and shoot	Apical cells of root and shoot are hexagonal in shape, they divided and redivide constantly
6. Cells associated with upward transport of water in plant	The cells of this region are cylindrical in shape.

Complete the table : (See Text Book Page 187)

Characteristics	Plant cell	Animal cell
1. Cell wall	A rigid cell wass formed of cellulose is present	Cell wall is abscent
2. Vacuole	Vacuoles are present	Vacuoles are absent
3. Plastid	Plastids are coloured bodies found only in plant cells	Plastid is absent
4. Centrosome	Centrosome is absent	Centrosome is present near the nucleus

(Complete the table : (See Text Book Page 187)

Correlate the words two columns : (See Text Book Page 187)

Answer the following questions : (See Text Book Page 180-189)

Find out the organ cedes, which perform a function synergistically.
(i) Helps in protein synthesis —

• Lysosome
• Ribdsomc.
• Nucleus
• Golgibody
• Cytoplasm
• ER
• Centrosomc. (IT) Secretory granules.
• Vacuole (Give tick Mark)

Or
(ii) Organelles help in synthesis, storage or secretion of different component —

• ER
• Golgjody
• Lysosome
• Secretory gram tiles

(c) Vacuole (Give tick mark)
Cell organelles functioning antagonistically (Find out)

(i) Synthesis of food and break down of food in plant cell.
Answer:
Mitochondria.

(ii) Synthesis of protein and decomposition or digestion of protein in animal cell.
Answer:
Ribosome.

Write origin of following cell organalles.
(i) Golgi body : Mitochondria/Cell membrane/ER.
Answer:
ER

(ii) Lysosome: Centrosome/Golgivody/ER
Answer:
Centrosome

(iii) ER: Cell membrane/Plastid/Golgi body.
Answer:
Cell membrane.

(iv) Ribosome: ER/Golgi body/Lysosome.
Answer:
ER

(v) Vacuoles of Animal Cell: Nucleus/Ccntrosome/Lysosome.
Answer:
Centrosome.

The terminal cells of nail and hair divide repeatedly and cause increase in length of nail and hair. Which organelle remains hyperactive in these cells?
Answer:
Golgi body.

Leucocytes digest and destroy pathogens inside themselves. During this period which originally increase in number?
Answer:
Lysosomes.

Which cell organelles are increased in number in cells of gastric gland (gland present in stomach) secreting enzymes immediately after taking meal?
Answer:
Mitochondria.

The movement of muscular cells of intestinal wall is very slow. But movement of skeletal muscles are fast. Which cell organelle more in number in the muscle cells of leg and hand?
Answer:
Mitochondria.

Class 8 Science Chapter 6 Question Answer West Bengal Board – The Structure of Living Organisms

Multiple Choice Questions & Answers : (1 mark for each question)

Question 1.
The smallest structural and functional unit of the body is —
i) tissue
ii) cell
iii) organ
Answer:
ii) cell

Question 2.
One ocular lens is used in —
i) electron microscope
ii) compound light microscope
iii) simple light microscope
iv) Complex light microscope
Answer:
iii) simple light microscope

Question 3.
The shape of red blood corpuscle is —
i) round
ii) spindle
iii) cylindrical
iv) hexagonal
Answer:
i) round

Question 4.
A function of muscular tissue of animal body —
i) stores fat
ii) absorption
iii) provides defence
iv) controls blood pressure
Answer:
iv) controls blood pressure

Question 5.
A function of corrective tissue of animal body —
i) secretion
ii) controls body temperature
iii) creates sound
iv) sesration of glands
Answer:
ii) controls body temperature

Question 6.
A function of nerve tissue of animal body —
i) receives stimulus
ii) controls body temperature
iii) swallowing of food
iv) stores fat
Answer:
i) receives stimulus

Question 7.
A function of permanent tissue in plant body —
i) formation of buds
ii) formation of new leaves
iii) formation of new organs
iv) repair of wounds
Answer:
iv) repair of wounds

Question 8.
Helps in cell division in animal cells —
i) Sysosome
ii) golgi bodies
iii) centrosome
iv) ribosome
Answer:
iii) centrosome

Question 9.
Saline environment is seen in —
i) river
ii) ocean
iii) pond
iv) canal
Answer:
ii) ocean

Question 10.
Excessive lysosomal activities lead to —
i) tuberculosis
ii) plague
iii) AIDS
iv) cancer
Answer:
iv) cancer

State whether True or False : (1 mark for each question)

1) Three lenses are used in compound light microscope.
2) Multicellular organisms can not adapt to the changing environment.
3) Only rod shaped cells are present in the retina.
4) An oval shaped cell is modified into a round shaped cell in case of cancer.
5) the dense, rounded structure present in the cytoplasmis called nucleus.
6) The coiled structure of DNA is called chromatin:
7) Vacuole plays important role in the formation of plant body.
8) Number of RBC decreases abruptly in animals living in high-altitude region.
9) Plants grown in saline water possess salt-filled cells.
10) Generally, larger vacancies are present in plant cell and smaller vacuoles in animal cell.
Answer:
1) true
2) false
3) false
4) true
5) true
6) false
7) true
8) false
9) true
10) true.

Fill in the blanks : ( 1 mark for each question)

1) ……………. is the smallest unit of a living organism.
2) Cell is seen is ……………. not seen by naked eye.
3) In 1674 Dutch scientist ……………. observed living cell for the first time.
4) ……………. consists of a single cell.
5) The organisms can adopt in the changing environment.
6) Algae like ……………. looks like a thread ie filamentous.
7) The shape of ……………. is even changing.
8) ……………. helps in the process of locomotion of Amoeba.
9) The ……………. present in human blood destroy the invading pathogens.
10) ……………. cells are the smallest cells in our body.
11) Muscle cells are ……………. shaped; both ends are
12) The ……………. cells are comperatively longer than other cells.
13) The adipose cell looks like a ……………. es.
14) ……………. cell is the longest cell.
15) Unfertilised ……………. egg is the largest cell.
16) ……………. provides a definite shape to cell.
17) The characters of parents are transmitted to the offspring through …………….
18) On the basis of ……………. number we differntiate one species from another species.
19) ……………. is the control centre of the cell.
20) ……………. are small rounded sacs filled with enzymes.
Answer:
1) cell
2) microscope
3) Lecnwen hock
4) amoeba
5) multicellular
6) spirogyra
7) amoeba
8) Pseudopodia
9) leucocytes
10) blood
11) spindle, tapering
12) nerve
13) ring
14) nerve
15) ostrich
16) cell membrane
17) genes
18) chromosome
19) nucleus
20) lysosomes

Very Short Questions & Answers : (1 mark for each question)

Question 1.
What is living thing?
Answer:
The things which perform respiration, digestion, excretion, and reproduction are called living things.

Question 2.
What is cell?
Answer:
The structural and functional unit of the body is called cell.

Question 3.
Who discovered cell?
Answer:
Cells were discovered by Robert Hooke in 1665 when he observed this a slice of cork under his microscope.

Question 4.
Is it possible to see a cell with naked eye?
Answer:
Cell is not seen under naked eye because its size is very small, it can be seen by microscope.

Question 5.
What is the magnification of an Electron Microscope?
Answer:
The magnification of an Election Microscope is 50.000-30,000

Question 6.
Name some unicellular organisms.
Answer:
Organisms like bacteria. Amoeba. Euglena, Paramecium, Chlamydomonas and yeast are formed of one cell only.

Question 7.
Name some multicelular organisms.
Answer:
Organisms like frog. man. tree. Hydra are formed of many cells.

Question 8.
On what factor the shape of cell depends in muliicelluar organisms?
Answer:
In multicellular organisms the shape of cell depends on their metabolic activities or nature of functions.

Question 9.
Where fat is stored in animals body?
Answer:
In animal body the fat is stored beneath the skin.

Question 10.
What type of cell is present in retina?
Answer:
Rod shaped cells are pescnt in ratina which absorbs mild light and cone shaped cells are also present in the retina which absorbs bright light and colour.

Question 11.
What is the shape of Dead store cells?
Answer:
Dead store cells present in seed coat and fruit coat assume the shape of rod, star or bone etc.

Question 12.
With what type of cell the body of Spirogyra is made of?
Answer:
The body of Spirogyra is made up of rectangular cells.

Question 13.
What Amoeba used for moving?
Answer:
Amoeba uses its pseudopodia for moving.

Question 14.
What is the shape of cell of RBC?
Answer:
Red blood Corpuscles are rounded and flattened on both sides, they look like a disc.

Question 15.
How do Muscles cells of human body look like?
Answer:
Muscle cells are spindle shaped both ends are tapering.

Question 16.
What is the shape of nerve cell?
Answer:
Nerve cells are quite long and are star-shaped or rounded and branches of different shapes remain connected with it.

Question 17.
What is the structural steps of living organism?
Answer:
The structural steps of living organism are — (body → organ system → organs → tissues → cell)

Question 18.
What is tissue?
Answer:
A group of cells performing the same function constitutes a tissue

Question 19.
What is cell membrane?
Answer:
The thin membrane present outside the cell is called cell membrane or plasma membrane.

Question 20.
What is cytoplasm?
Answer:
Cytoplasm is a jelly-like semifluid substance between the cell membrane and nucleus.

Question 21.
What is called ‘brain’ of the cell?
Answer:
Nucleus is called the ‘brain” of the cell as it controls all biochemical process of cell.

Question 22.
What is chromatin reticulum?
Answer:
A thread-like structure present inside nucleus arranged is reticulate fashion are called chromatin reticulum.

Question 23.
What are chromosome?
Answer:
Chromosomes are formed from chromatin reticulum. During cell division, Chromatin fibres condense to form chromosomes.

Question 24.
What is gene?
Answer:
Gene is a special structure present in chromosome. The characters of parents are transmitted to the offspring through genes.

Question 25.
What is nucleolus?
Answer:
A distinct, rounded, dense, structure is present inside the nucleus where rebosomes are synthesised, it is called nucleolus.

Question 26.
How many chromosomes are there in human body?
Answer:
A human body cell has 46 chromosomes in its nucleus.

Question 27.
What are prokaryotes?
Answer:
Cells like Bacteria, blue-green algae posses nuclear material without enclosed in membrane, they are prokaryotes.

Question 28.
What are eukaryotes?
Answer:
Most of the plant and animal cells possess nucleus with membrane and nuclear reticulum, they are called eukaryotes.

Question 29.
What is protoplasm?
Answer:
Together nucleus and cytoplasm are called protoplasm.

Question 30.
What are cell organelles?
Answer:
Various minute structures scattered inside cell cytoplasm are called cell organelles.

Question 31.
What is called the power house of cell?
Answer:
Mitochondria is called the power house of ceil?

Question 32.
What are cristae?
Answer:
Finger like projections come out from inner membrams of Mitochondria they are called cristae.

Question 33.
What are called suicidal bag?
Answer:
Lysosomes are called suicidal bag.

Question 34.
What leads to cancer?
Answer:
More lysosomal activities leads to cancer,

Question 35.
What is primordial entriclc?
Answer:
The large vacuole occupies most of the plant cell centrally, pushing the cytoplasm and nucleus towards periphery in the form of a film just beneath the cell membrane, this layer is called primordial utricle.

Question 36.
Which animals have antifreeze protein?
Answer:
The animals living in very dry and cold environment have anti freeze protin.

Question 37.
How fresh water plants float on water?
Answer:
They can easily float on the surface of water due to air cavity in the parenchyma (aerenchyna).

Question 38.
In less oxygenated environment what helps bacteria in respiration?
Answer:
If less oxygenated environment mitochondria are absent in bacteria instead they possess mesome which helps them in respiration.

Question 39.
What is more in cells of endoskelcton?
Answer:
Calcium is more in cells of endoskeleton.

Question 40.
What increases abruptly in animals living in high altitude region?
Answer:
Number of RBC increases abruptly in animals living in high altitude region.

Short Questions & Answers : (2 marks for each question)

Question 1.
What does a cell look like?
Answer:
The shape of cells varies from one organism to another. The shape of cells is related to the functions they perform. Cells may be rounded, spherical, oval, elongated, tubular, cubojdal, disc-shaped, kidney shaped, spindle shaped or irregular.

Question 2.
What is a tissue? Into how many groups it can be classified?
Answer:
Division of labour in protoplasm of different cells results from the evolution life and causes the difference in functions. Due to occurrence of these type of phepiornena specialised types of cells originated. Collection of these specialised cells are known as tissue. Tissues can be divided into the following types :

• Plant tissues
• Animal tissues.

Question 3.
What are the different types of plant tissues?
Answer:
Plant tissues are mainly classified as —

• Meristematic tissues
• Permanent tissues

Question 4.
What are the different types of animal tissues
Answer:

• Epithelial tissues
• Connective tissues
• Muscular tissues
• Nervous tissues.

Question 5.
What are different parts of an animal cells?
Answer:
Animal cells have following parts – Cell membrane, Cytoplasm, Nucleus, Cell organelles, Mitochondria, Endloplasmic Reticulum, Golgibodies, Lysosomes, Ribosomes and Centrosome.

Long Questions & Answers : (3 marks for each question)

Question 1.
Which organs in human body are capable of performing one or more than one functions?
Answer:

• Stomach and small intestine for digestion of food.
• bung for respiration
• Heart for transperation of blood (circulation)
• Kidney for elimination of metabolic waste (excretion)
• Brain for receiving external stimulus and converting it into response.

Question 2.
How many types of Microscope arc there, explain briefly?
Answer:
a) Simple light Microscope : Structurally it is simple because only one ocular lens is used. Its magnification is 15-20x.

b) Compound light Microscope: Three lenses are used, namely – ocular lens, objective lens and condenser lens. It is operated by using a beam of sunlight or artificial light source. A mirror or reflector is used fortius purpose. Its magnification is 2000 – 400.0x.

c) Electron Microscope : In this microscope eletromagnetic lens is used instead of glass lens. Magnification is 50,000 – 30,000x. It is fully computerized. The materials to be observed cannot by seen directly. Instead of that photographic films are used.

Question 3.
What types of physiological function are going on in an animal body?
Answer:

• Digestion, Absorption, Assimilation and Egestion (Nutrition)
• Gaseous exchange and Energy production (Respiration)
• Transport of food, oxygen and carbon dioxide (Circulation)
• Expulsion of harmful metabolic wastes (Excretion)
• Change of place in search of food, shelter etc. (Locomotion)
• Response to external stimulus (nervous co-ordination)
• Increase in number and perpetuation (Reproduction)

Question 4.
Describe the different functions that occur in plants throughout a day.
Answer:

• Transport of water from soil to the leaves.
• Absorption of sunlight and preparation of food.
• Standing erect.
• Storage and transport of food.
• Formation of flower, fruit and seeds.

Question 5.
What are the functions of meristematic tissue?
Answer:

• Formation of new’ organs.
• increase the length of root and shoot.
• formation of new leaves, axillary buds, new branches and flowers.
• formation of protective coverings.
• formation of conductive tissue.

Question 6.
What are the functions of permanent tissues?
Answer:

• Synthesis, storage and transporation of food.
• Conduction of water.
• Providing mechanical strength and rigidity
• Storage of waste
• Proving buoyancy
• Dispersal of fruits and seeds
• Increasing the power of tolerance of plant organs to external load and pressure.
• Repair of wounds

Question 7.
Describe the functions of Epithelial tissues?
Answer:

• Formation of protective layers over the free surface of internal organs and outside the body
• Absorption
• Secretion
• Elimination of metabolic wastes and foreign substances.
• Formation of exoskeleton (Scale, hairs, nails, hoove, horn etc.)

Question 8.
What are the functions of nerve tissues?
Answer:

• Receives stimulus
• Conduction of impulse
• Co-ordination of internal and external environment
• Controls contraction of muscle and secretion of gland.

Question 9.
Briefly explain the functions of connective tissue?
Answer:

• Providing mechanical strength and framework,
• Connects different internal organs
• Provides defence
• Stores fat and controls body temperature.

Question 10.
What are the functions of muscular tissues?
Answer:

• Movement of appendages
• Helps in locomotion, swallowing of food, peristaltic movement of alimentary canal and primary tract.
• Controls heart beat and flows of blood,
• Controls blood pressure.
• Controls facial Expression
• Causes changes in body postures and gestures.

Question 11
What is ceil wall? what are its functions?
Answer:
The external matrix present around the plant cell is cell wall. It is a non-living, strong and rigid layer surrounding plasma membrane. It is mainly composed of cellulose. Functions of cell, wall are –

• Gives rigidity and shape to the plant cell.
• Allours substances in solution to enter and leave the cell without hindrance.
• Provides protection

Question 12.
Write short notes on – (a) Nucleus, (b) Mitochondria, (c) Ribosomes
Answer:
a) Nucleus — The dense, rounded structure present in the cytoplsm is called Nucleus. It controls all bio-chimical processes of cell, so it is called ‘brain’ of the cell, Nuclear membrane exists outside the nucleus. Semi-liquid nucleoplasm is present inside it. contains network of thread-like structures called chromatin fibres which contain DNA. A distinct, rounded, dense structure is present inside the nucleus where ribosomes are synthesised. It is called nucleolus.

b) Mitochondria — It is rounded oval or rod-shaped. Various types of enzymes, ribosome and nuclic acid (DNA) are present inside its matrix. They produce energy by breaking down nutrients of food. Finger-like projections come out from inner membrances, it is called cristac. They are involved in production of energy (ATP).

c) Ribosomes — Ribosomes are scattered in the cytoplasm of prokaryotes or attached on surface of ER. These are membraneless cell organelles. Protein synthesis is the main function of ribosome. These proteins help in recovery of wounded protions and also helps in new cell formation.