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Dear students, prepare for biology class 9th chapter 4 long questions. These important long questions are carefully added to get you best preparation for your 9th class biology ch. 4 exams.
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Question: 1
Describe the types of microscopes.
Answer: 1
Question: 2
Describe the history of formulation of cell theory?
Answer: 2
Question: 3
Construct the time line that traces the history of formulation of the cell theroy.
Answer: 3
Question: 4
Write a note on Cell wall.
Answer: 4
Ans. Cell Wall Introduction The cell wall is a non-living strong component of the cell and it is located outside the plasma membrane. Not all living organisms have cell walls around their cells e.g., animals and many animal like protists. Function It provides shape, strength, protection and support to the inner living matter (protoplasm) of the cell. Chemical composition Plant cells have a variety of chemicals incorporated in their cell walls. Types Primary wall (Lahore board 2012 G II) The outer layer of the plant cell wall is known as primary wall and the cellulose is the most common chemical in it. Secondary Wall (Lahore board 2012 G II) Some plant cells, for example xylem cells also have secondary walls on the inner side of the primary wall. It is much thicker and contains lignin and some other chemicals. Plasmodesmata There are pores in the cell walls of adjacent cells, through which their cytoplasm is connected. These pores are called plasmodesmata. Cell wall of Fungi Fungi and many other protists have cell walls although they do not contain cellulose. Their cell walls are made of variety of chemicals. For example, chitin is present in the cell wall of fungi. Cell wall of prokaryotes Prokaryotes have a cell wall composed of peptidoglycan that is a complex of amino acids and sugar.
Question: 5
Write a note on Cell membrance.
Answer: 5
Question: 6
Write a note on nucles.
Answer: 6
Question: 7
Write a note on Plastids.
Answer: 7
Question: 8
Write the relationship between cell size and shape and surface area to volume ration.
Answer: 8
Ans. Relationship between cell size and shape Cells vary greatly in size. Smallest Cells The smallest cells are bacteria called Mycoplasmas with diameter between 0.1gm to 1.0pm. Bulkiest Cells The bulkiest cells are bird eggs. Longest Cells Longest cells are some muscle cells and nerve cells. Most cells lie between these extremes. Relation of cell size and shape to cell function Birds Egg Bird's eggs are bulky because they contain a large amount of nutrient for the developing young. Muscle Cells Long muscle cells are efficient in pulling different body parts together. Nerve Cells Lengthy nerve cells can transmit messages between different parts of body. Benefits of small cell size Small cell size also has many benefits. For example human red blood cells are only 8t_tm in diameter and therefore can move through our tiniest blood vessels i.e. capillaries. Surface area of large and small cells Large cells have less surface area in relation to their volume while small cells of the same shape have more surface area. The figure shows relationship using cube shaped cells. The figure shows one large cell and 27 small cells. In both cases the total volume is the same: Volume = 30p.m x 30p.m x = 270001=3 Contrast or Comparison of total volume to total surface area In contrast to the total volume, the total surface area are very different because the cubical shape has 6 sides. Its surface area is 6 times the area of 1 side. The surface areas of The cubes are as follows. Surface area of 1 large cube = 6 x (301= x 3011m) = 5400p,m2 Surface area of 1 small cube = 6 x Surface area of 27 small cubes = 27 x 600p.m2 = 162001= Role of Surface Area The need of nutrients and rate of waste production are directly Proportional to cell volume. The cell takes up nutrients and excretes wastes through its surface cell membrane. So a large volume cell demands large surface area. A large cell has much smaller surface area relative to its volume than smaller cells have. Hence it is concluded that the cell membrane of small cells can serve their small volumes more easily than the membrane of the large cell.
Question: 9
Descirbe the passage of molecules into and out of cells.
Answer: 9
Question: 10
Describe Different types of animals tissues.
Answer: 10
Question: 11
Q<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15857376594001076335476"> )</gwmw> 5) a Write a note on <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15857376556141678435537">meristematic</gwmw>Tissuses?
Answer: 11
There tissues are composed of cell. Which have the ability to divide the cell are thin walled have large nucleus and small or no values
Apicla meristerms:
Located at the apices of roots and shoot. When they divide they cause increase in the length of plant such growth is called primary growth
Lateral meristerns:

are located on the lateral sides of roats and shoat by dividing they are responsible for increase in growth is called secondary growth.
Vascular cambium: Located between xylem and phloem and cork combiumin the the auterlateral sides of planet
Question: 12
Q NO 5<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15857379101724271126350">(</gwmw>B) What <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15857379101727116785915">is diffusion explain</gwmw> with examples?<div><br></div>
Answer: 12
A Diffusion is the movement of molecules from an area of higher concentration to the area of lower concentration along concentration the maleculesof any substance are in motion when that substances is above 0 degree centigrade. In substance, majority of the molecules move from higher to lower concentraion although there are some that move law to high the overall movement is thus from high to law concentration. Eventually the molecules reach a state of equilibrium where they are distributed equally throughout the area Diffusion is one principle method of movement of substance within cell as well as across well membrane . Carbon, dioxide, oxygen, glucose etc. can cross cell wall membrain by diffusion . example of diffusion Because a cell does not expend energy when molecules diffuse across its membrane the diffusion is type of passive transport.
Question: 13
Q no 6 (a) Describe the cell function and cell structure?
Answer: 13
The bodies of animals and plant are made of different cell type each type performs specific function and all coordination function became the life processes of organisnscells may one type may differ from those of other type in the following respects
Size and Shapes:
Red blood cell are round to accommodate globular hemoglobin.
Nerve cells are long for the transmission of nerve impulse.
Xylem cell are tube -like and have thick wall of conduction of water and support.
Surface are to volume ratio:
Root hair cell have large surface area of the maximum absorption of water and salts.
It on be explain by the following examples of cell of human body.
Never cell conduct nerve impulse and thus contribute in coordination in body .Muscle cell undergo contraction and share their ralein movement in body.
Red blood cell carry oxygen and white blood cell kill foregin materials and So contribute in the rules of blood in transportationand defense .
Question: 14
Q no 6 (b) Describe the structures and function of <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15857439153463844989312">nucleus</gwmw>?
Answer: 14
Organelles are small structures within cells that perform dedicated function
A prominent nucleus occur in eukaryrtic cell, In animals cell it is present in the center while in matureplants cells . due to the formation of large central vaciuale. it is pushed to side nucleus is bounded by a double membrane know as nuclear envelape. Nuclear envelope contain many small pores that enable it to acttas a semi-permeable membrane
Nucleolus is dark spot and it is the site where ribosome RNA are formed and assembled as ribosomechromosome are visible only during cell division while during interphaseof cell they are in the form of fine thread-likestructure known as chromation
theprokaryotic cells do not contain prominent nucleus.

their chromosome is made of 'DNA only submerged cytoplasm
Question: 15
Q no 7 (a) Write a <gwmw class="ginger-module-highlighter-mistake-type-2" id="gwmw-15857479630634556260259">shot</gwmw> note on Lysosomes:<div><br></div>
Answer: 15
In the mid- twentieth unturya belgionscientist christian Rene deduve. discovered lysosomes. these are single membrane bound-organielles lysomes contain strange digestive emymesand work for the breakdown of focal and waste materials within cell during its function a lusomefuses with the cacuolethat contain the tergetedmaterials and its eneymesbreakedown the materials
Question: 16
Q no 7 (b) Write note on mitochondria and endoplasmicreticulum?
Answer: 16
Mitocnoridria are double membrane-bounded structure formed only ineukaryotes.
These are the sites of aerabic respiration. and are the major eergyproduction center the outer membranceof aMitocnoridrian issmall
but the inner membrane forms many infaldingMitocnoridriahave their own DNA and ribosemes. The ribosomesof mitochoridrionare moesimilar to bacterial ribosometo bacterial ribosome
Ensoplamicrericulum is a network of intercountedchamnelsthat extends from cell membrane to nuclear encelop. The network exist in two forms
Rough Endoplasmic Reticulum:
is so named because of its rough appearance due to numerous ribosomes that are attached to it
Smooth endoplasmicReticulum:
Lackes ribosomesand is inalevedin lipid metabrlismand in the transport of materials from one part of cell to other
Question: 17
Define micrscopy . What are characteristics of a microscope ? What are types of microscope ?
Answer: 17
Microscopy :
The use of Microscope is known as microscope . The first compound microscope was developed by Zacharias Janssen , in Holland in 1595 . It was simply a tube with lenses at each and its magnification ranged from 3X TO 9X
Question: 18
What is light microscope ?
Answer: 18
Light microscopeworks by passing visible light through the specimen
Construction :
It uses two glass lenses . One lens produces an enlarged image of the specimen and the second lens magnifies the image and projects it into viewer's eye or onto photographic film
Question: 19
What is electron microscope ?
Answer: 19
Electron microscope :Electron microscope is the most advanced form of microscope
Construction :
In EM , object and lens are placed in a vacuum chamber and a bean of electrons is passed through object . Electrons pass through or are reflected from object and make image . Electromagnetic lenses enlarges and focus the image onto a screen or photographic film

Question: 20
Explain the history of cell theory .
Answer: 20
Aristotle : He presented the idea that all plants and animals are somehow related

Robert Hooks :In 1665 , he examined a thin slice of cork and observed many tiny empty compartments are called cellulose . So He discovered cell

Antonie van Leeuwenhoek :He observed micro-organisms in pond water by his self-made microscope and called then animalcules
Question: 21
What are sub-cellular and acellular particles ?
Answer: 21
According to the first principle of the cell theory all organisms are composed of one or more cells . Virus ,prions and viroids are not composed of cells , rather they are sub-cellular or a cellular particles . They do not run any metabolism inside them . They show some characteristics of living organisms i-e they can increase in number and can transmit their characters to next generation . We knows that such acellular particles are not classified in any of the five kingdoms of organisms
Question: 22
What are the principle of cell theories ?
Answer: 22
1: All organisms are composed of one or more cells
2: Cells are the smallest living things , the basic unit of organization of all organisms
3: Cells arise only by divisions in the previously existing cells
Question: 23
Explain the following cellular structure
Answer: 23
1: Cell wall : Cell wall is a strong and non-living component of cell present outside the plasma membraneFunction : It provides shape , strength , protection and support to the inner living matter called protoplasm cellsPresence : Cell wall is present in plants , plant like protists , fungi and prokaryote but absent in animals and animal like protists
Question: 24
Write a note on cell organelles?
Answer: 24
Cell organelles: Organelles are small structure with in cells that perform dedicated functions
Nucleus :
Presence : A prominent nucleus is present in eukaryotic cells
Location :
In animals cells : In animal cells it is present in the centre
In plant cell : In mature plants cells , due to the formation of large central vacuole it is pushed to side
Structure of Nucleus :
Nuclear envelope : Nuclear is bounded by double small membrane which is called nuclear envelope . Nuclear envelope contains of many small pores that enables it to act as a semi-permeable membrane
Nucleoplasm : Inside the nuclear envelope a granular fluid is present which is called nucleoplasm . Nucleoplasm contains one or two nucleoli (Singular nucleolus) and chromosomes

Nucleolus : Nucleolus is a dark spot and is the where ribosomal RNA is formed and assembled as ribosomes

Chromosome : They are visible during cell divisions while during interphase (non-dividing phase) of the cells . It is present in the form of thread like structure called chromatin chromosomes are made up of deoxyribonucleic acid (DNA) and proteins
Question: 25
Compare prokaryotes cell and eukaryotic cell<div>Similarities :</div><div><br></div>
Answer: 25
There are few similarities between prokaryotic and eukaryotic cells
1: They both have DNA as their genetic prokaryotic and eukaryotic cells
2: They are both membrane bounded
3: They both have ribosomes
4: They have similar basic metabolism
5: They are both amazingly diverse in form
Question: 26
Differentiate between an animal cell and plant cell<div><br></div>
Answer: 26
Animal cell:
1: A cell membrane is the outer most boundary of an animal cell . Cell wall is absent
2: Centrioles are present in animal cells
3: An animal cell may contain numerous sized vacuoles
Position of nucleus
4: The position of nucleus is usually central
5: There are no plastids in animal cell and hence they cannot manufacture their own food material

Question: 27
Explain relation between cell structure and cell function<div><br></div>
Answer: 27
Cell structure is always in accordance with their function . Cell differ of one type to the other type of cells in the following way
Size and shape :
1: Red blood cells are round to accommodate globular haemoglobin
2: Nerve cells are long for the transmission of nerve impulses
3: Xylem cells are tube-like and have thick walls for conduction of water and support

Question: 28
Describe the cell unit of life in term of its structure and function<div><br></div>
Answer: 28
Cell unit of life :
Various cells have various structures but when they perform function in coordination with each other then they become unit of life . It means there is a division of labor among the cells of an organism . The phenomenon is common to both animal and plant cells

Animal cells :
Different cells are specialized for different functions in animal e.g
1: Nerve cells conduct nerve impulse and thus contribute in coordination in body
2: Muscle cells undergo contraction and share their role in movement in body
3: Red blood cells carry oxygen and white blood cells kill foreign agents and so contribute in the roles of blood in transportation and defense
4:Some skin cells act as physical barriers against foreign materials and some as receptors for temperature , touch , pain etc
5: The cells of bone deposit calcium in their extracellular spaces to make the bone tough and thus contributes to the supporting role of bones
Question: 29
How cell work as an open system ?
Answer: 29
A cell works an open system i-e it takes in substance needed for its metabolic activities through its cell membrane . Then it perform the metabolic processes assigned to it .Products and by-products are formed in metabolism . Cell either utilizes the products or transports them to other cells . The by-products are either stored or are excreted out of cell
Question: 30
Explain different phenomenon of transport across a semi permeable membrane
Answer: 30
Diffusion : It is the movement of molecules from an area of higher concentration to the area of lower concentration i-e along concentration gradient

Explanation: The molecule of any substance (solid, liquid or gas ) are in motion when that substances is above 0 degrees Kelvin or -273 degrees centigrade . In a substance , majority of the molecules move from higher to lower concentration , although there are some that move from low to high . The overall (or net ) movement is thus from high to low concentrations . Eventually , the molecules from small intestine lumen into the blood capillaries of villi is another example of diffusion

Passive transport : In diffusion cell does not spend energy when molecules diffuse across its membrane , the diffusion is type of passive transport
2: Facilitated diffusion : When a transport protein moves a substance from higher to lower concentration , the process is called facilitated diffusion
Explanation : The rate of facilitated diffusion is higher than simple diffusion . Facilitated diffusion is also a type of passive transport because there is no expenditure of energy in this process
3: Osmosis : Osmosis is the movement of water across a semi-permeable membrane from a solution of lesser solute concentration to a solution of higher solute concentrations

Tonicity : It refers to the relative concentrations of solute in the solution being compared
Types of solution :
Hypotonic : Solution with relatively lower solute concentrations
Hypertonic : Solution with relatively higher solute concentrations
Isotonic :Solution having equal amount or concentrations of solute

Question: 31
What do you know about endocytosis and exocytosis ?<div><br></div>
Answer: 31
Endocytosis :
Definition : It is the process of cellular ingestion of bulky materials by the infolding of cell membrane
Steps of Endocytosis :
-A portion of cell membrane invigilates
-The material from outside is taken inside invagination
-The open ends of invagination seal and form a small vesicle
-The vesicle detach from the cell membrane and moves into cytoplasm
Types Of Endocytosis :
It has two forms
Exocytosis : The process through which bulky material is exported

Question: 32
What are tissues ?Describe different types of animal tissues .
Answer: 32
Tissues :
Tissues as a group of similar cells specialized for the performance of a common function .
In a colony of cells there are many cells and each cell performs all general functions on its own . Such a group does not get tissue level of organization because cells are not specific and there is no coordination among them
Types of tissues :
There are two types of tissues
1: Animal tissues
2: Plant tissues
1: Animal tissues
These are of four major categories
1: Epithelial tissues 2: Connective tissues

1: Epithelial tissues: Epithelial tissues covers the outside body and lines organs and cavities . The cells are closely packed together in this tissues . The tissues has many types on the basis of shape of the cells and number of cell layer
Types :
It is divided into following types :
1: Squamous Epithelium :
It consists of single layer of flat cells
Location : It is present in lungs , heart , and blood vessels
Function : It allows material to pass across it
2: Cuboidal epithelium :
It consists of single layer of cube shaped cells
Location : It is present in kidney tubes and small glands
Function : They make secretions
3: Columnar epithelium :
It consists of elongated cells
Location : It is present in alimentary canal and gall bladder
Function : They make secretions
4: Cilliated Columnar epithelium :
It consists of elongated cells with cilia
Location : It is present in bronchi and trachea
Function : The propels in trachea and bronchi
5: Stratified squamous epithelium :
They have many layers of flat cells
Location : It is present in the lining of oesophagus and mouth and also over the skin
Function : It protects the inner parts

Question: 33
Explain different types of plant issues
Answer: 33
Plant tissues : As in animals , the cells of plants are grouped into tissues with characteristic functions such as photosynthesis , transport etc

Types :
Plant tissues are of two major categories
1: Simple tissues 2: Compound tissues
Simple tissues : Tissues which are made up of single type of cell are called simple tissues
Types :
It is of two types
1: Meristematic tissues
2: Permanent tissues
-Meristematic tissues : These tissues are composed of cells ., which have the ability to divide . The cells are thin walled have large nucleus and small or no vacuoles . They do not have inter-cellular spaces among them
Types :
The main types of meristematic tissues are recognized in plants
1: Apical meristem 2: Lateral meristem
Apical meristem: : Apical meristem are located at the apices (tips) of roots and shoot . When they divide they cause increase in the length of plant . Such growth is called primary growth
Lateral meristem: lateral meristem are located on the lateral sides of roots and shoot . By dividing they are responsible for increase in growth of plant parts . This growth is called secondary growth

Types :
They are of two types
Vascular cambium
present between xylem and phloem
Cork cambium
Present in the outer lateral sides of plants