Categories
Class 10th Science

Sexual Reproduction in Plants : Science Notes for Class 10 Biology

SEXUAL REPRODUCTION

  • In a population variations are useful for survival of a population.
  • Sexual mode of reproduction allows individuals to have more variations to be generated.
  • Generation of variations in DNA copying mechanism of asexual mode is fairly slow
  • Each new variation is made in a DNA copy that already has variations accumulated from previous generations.
  • Combining variations from two or more individuals would thus create new combinations of variants.
  • Each combination would be novel, since it would involve two different individuals.
  • For each new cell to not have twice the amount of DNA that previous generation have, special lineages of cells in specialised organs have only half the number of chromosomes and DNA as compared to other cells.
  • Two individuals combining during sexual reproduction, result in re-establishment of the number of chromosomes and DNA content in new generation.
  • Motile germ cell is called male gamete and germ-cell containing food is called female-gamete

Sexual reproduction in flowers

  • Flower can be termed as the sexual organ of a plant.
  • All the parts of a flower are arranged around an axis.
    1. Sepals: Green leaf like structure.
    2. Petals: Colourful structures, which add attraction to a flower. This attraction is not only having ornamental value, but a more important role in facilitating reproduction. Insects and birds, attracted by the colour, help transfer pollen grains or male gametes from male flower to female flower. This helps in pollination.
    3. Male Reproductive Organ of Plant: Androecium
  • The flower of a plant contains tube like structures called stamen.
  • At the top of stamen is a chambered structure called Androecium.
  • Androecium is responsible for the production of male gamete also called pollen grains.
    4. Female Reproductive Organ of Plant:
  • GynoeciumUsually at the centre of a flower you can notice Gynoecium.
  • Gynoecium is pitcher shaped structure with a long tube protruding out of it.
  • The gynoecium produces female gamete also called eggs.

Difference between Unisexual and Bisexual Plants

Unisexual Bisexual
  • A flower containing either stamen or carpel is unisexual e.g.watermelon
  • Flower containing both stamen and carpel are bisexual e.g hibiscus
  • Stamen is the male-reproductive part producing pollen which is yellowish in color.

 

  • Stamens and carpels are the reproductive parts of a flower.
  • Carpel is present in the centre of the flower and is the female reproductive part.
  • Carpel is made up of three parts , the swollen part is ovary , the middle elongated part is style and the terminal part is sticky and called stigma.
  • The ovary contains ovule which has an egg cell, the male gamete fuses with the female gamete present in ovule.

Pollination In flower

  • Pollination is the transfer of pollen from a male part of a plant to a female part of a plant, later enabling fertilisation and the production of seeds.
  • The pollen needs to be transferred from stamen to the stigma.
  • If the transfer of pollen occurs in the same flower it is self-pollination, if the transfers occurs in a different flower it is called cross-pollination
  •  Cross pollination can be facilitated by insects, birds, animals, air or water.
  • A tube growing out of the pollen grain and travels through the style to reach the ovary helps the landed pollen grain to reach female-germ cell.

Zygote Formation in Plant Reproduction

  • Once pollen grains enter the androecium, one of them enters the egg to fertilize it to form a zygote.
  • Seeds are the zygote or embryo of the plant.
  • To survive and to germinate,  seeds need source of food.
  • In all seeds there is abundance of food.
  • That is why for our daily need we depend on so many seeds like rice, wheat, groundnut for food.
  • During germination the food in the cotyledon is used to grow a new plant.
  • Once green leaves come out, they take care of further food production
  • After fertilization the zygote develops several times to form an embryo within the ovule.
  • The ovule develops a tough coat and is gradually converted into a seed
  • The seeds contain the embryo which develops into a seedling under proper conditions, this is known as germination

 

Appear the Quiz on Reproduction Topic 

Categories
Class 10th Science

How do Organism Reproduce:Class 10th Science Notes on Biology

Reproduction 

  • Reproduction is defined as a biological process in which an organism gives rise to young ones (offspring) similar to itself.
  • Reproduction at its basic level involves creation of the copy of DNA
  • DNA present in the chromosome of the cell is the information source for making proteins.
  • If the information is changed, different proteins will be made, and would lead to altered body designs.
  • The two DNA’s need to be separated, for the copy of DNA to have an organised cellular structure, DNA copying is accompanied by creation of additional cell apparatus.
  • Since no bio-chemical reaction is absolutely reliable, therefore the copying of DNA will have some variations each time.
  • DNA copies generated will be similar to each other and not identical.
  • Some of the variations may even be drastic enough for the new DNA generated not would not be able to work with the cellular apparatus and would eventually lead to death of the new cell.
  • The consistency of DNA copying during reproduction is important for maintenance of body design features that allow the organism to use a particular niche .
  • Reproduction is linked to stability of population of species.

IMPORTANCE OF VARIATION in Reproduction 

  • Population of organisms fill well-defined places or niches in the ecosystem, using their ability to reproduce.
  • Variation in DNA copying can ensure the survival of some individuals among a population, in case of changes in a particular niche in which the population is suited to survive in.
  • Variation is useful for survival of species over time.

ASEXUAL REPRODUCTION

  • Asexual reproduction:A sexual reproduction involves production of Offsprings by single parents.
  • There is no involvement of specialized gamete cell .
  • Offspring are genetically identical to their parents

Types of  Asexual Reproduction 

FISSION

  • In unicellular organisms, fission is the mode of reproduction used to create new individuals.
  • In simple unicellular organisms fission can take place in any plane, such as in amoeba.
  • In organisms showing somewhat more organisation of body, it occurs in a definite orientation in relation to the structure, for example leishmania having a whip-like structure present in one end.
  • Some single-celled organisms simply divide into many daughter cells simultaneously using multiple fission, for example plasmodium.
  • Yeast can put out small buds that separate and grow further

FRAGMENTATION

  • Multicellular organisms with simpler body design use fragmentation as a method of reproduction, for example in spirogyra, which breaks up into smaller pieces upon maturation.
  • These fragments grow into new individuals.
  • Not all multicellular organisms can use cell by cell division for reproduction as they are not simply a random collection of cells, and have organised body designs and structures,
  • In multicellular organisms reproduction via a single cell-type which is capable of growing, proliferating and making other cell types under right circumstances.

REGENERATION

  • Many fully differentiated organisms have the ability to give rise to new individuals from their body parts.
  • For example , if hydra or planaria is cut or broken into any number of pieces each piece grows into a complete organism this is known as regeneration
  • It is not the same as reproduction, since organisms would not depend on being cut up to be able to reproduce.

Budding

  • Organisms such as hydra use regenerative cells for reproduction in process of budding.
  • In hydra a bud develops as an outgrowth due to repeated cell division at one specific site
  • These buds develop into tiny individuals and detach themselves from parent body when fully mature.
Budding In Hydra
Budding In Hydra

Vegetative propagation

  • There are many plants in which parts like roots, stems and leaves can develop into new plants in appropriate conditions, this property is used in vegetative propagation method such as layering or grafting
  • Plants raised by vegetative propagation can bear fruits and flowers earlier than those reproduced by seeds.
  • Plants raised by vegetative propagation are genetically similar enough to the parent plant to have all its characteristics.

Spore formation

  • In rhizopus tiny blob-on-a-stick structures called sporangia containing spores that can develop into new rhizopus are involved in reproduction.
  • The spores have thick walls that protect them until they come into contact of another moist surface and being to grow.
Spore formation in rhizopus
Spore formation in rhizopus

Read the NCERT Solution On Reproduction here

Categories
Class 9 Science

Diversity in Living Organism:Animalia Class 9th Science Notes

ANIMALIA

Porifera

  • These are non-motile organisms with pores all over their body leading to canal system that helps in circulating water throughout the body to bring in food and oxygen.
  • These animals are covered with a hard outside layer or skeleton
  • They are commonly called sponges example- sycon, spongilla and euplectelia.

Coelenterata

  • The body of these animals have a cavity, and is made up of two layers of cells.
  • Some of these species live in colonies(corals) while others have solitary like span(hydra).

Platyhelminthes

  • The body of these animals are bilaterally symmetrical, and have three layers of cells and are thus called triploblastic.
  • The three layers of cells allow outside and inside body linings as well as some organs to be made.
  • There is no true coelom, in which well developed organs can be accommodated.
  • The body is flattened from top to bottom i.e dorsoventrally.
  • Examples are parasites like liver flukes or free-living animals like planarians.

Nematoda

  • The nematoda body is bilaterally symmetrical, triploblastic and cylindrical.
  • There are tissues but no organs and have a psuedo cavity
  • Examples of nematoda are worms causing elephantiasis i.e filarial worms and pinworms found in intestines.

Annelida

  • Annelida are bilaterally symmetrical, triploblastic and have a true body cavity, allowing organs to be packed in body structure.
  • Differentiation occurs in a segmental fashion with segments lined up one after the other from head to tail.
  • Earthworms and leeches are examples of annelida.

Arthropoda

  • This is the largest group of animals
  • They are bilaterally symmetrical, segmented, and have an open circulatory system and jointed legs.
  • The coelomic cavity is blood filled in arthropoda.
  • Examples of arthropoda are prawns, butterflies, scorpions and crabs.

Mollusca

  • They are bilaterally symmetrical, have reduced coelomic cavity and little segmentation
  • They have open circulatory system, kidney like organs for excretion and use foot for moving around
  • Example are snails and mussels.

Echinodermata

  • These are spiny skinned, free-living marine animals.
  • They are triploblastic, have a coelomic cavity and have peculiar water driven tube system that they use for moving around
  • They have hard calcium carbonate structures as skeleton.
  • Examples of echinodermata are starfish and sea urchins.

Protochordata

  • They are bilaterally symmetrical, triploblastic and have notochord.
  • Notochord is a long rod-like support structure that runs along the back of the animal separating the nervous tissue from the gut.
  • Protochords may not have a proper notochord present at all stages in their lives
  • Examples of protochords are balanoglossus, herdermania and amphioxus.
Balanoglossus
Balanoglossus

Vertebrata

  • These animals have a true vertebral column and internal skeleton, allowing a completely different distribution of muscle attachment points to be used for movement.
  • They are bilaterally symmetrical, triploblastic, coelomic, segmented, dorsal nerve chord, paired gill pouches.

(i) Pisces

  • These are fish.
  • Their skin is covered with scales, they obtain oxygen dissolved in water using gills, have a streamlined body and a muscular tail.
  • They are cold-blooded, have two chambered heart and lay eggs
  • Examples are tuna, rohu and angler fish.

(ii)Amphibia

  • They lack scales, have three-chambered heart and mucus glands in their skin .
  • They respire through gills or lungs and lay eggs.
  • Examples of amphibia are salamanders and hyla.

(iii)Reptilia

  • These animals are cold-blooded, have scales, lay eggs, have three chambered heart and respire through lungs
  • Crocodiles have four-chambered heart.
  • Turtles, lizard and chameleon are examples of reptiles.
Nile crocodile

(iv)Aves

  • They are warm-blooded, have four chambered heart, lay eggs and have an outside covering of feathers.
  • They have two forelimbs modified for flight and breathe through lungs
  • Examples are ostrich, crow, sparrow etc.

(v)Mammalia

  • Mammals are warm-blooded, have mammary glands for production of milk to nourish young ones.
  • Their skin have hair as well as sweat and oil glands
  • Platypus and echidna lay eggs.
  • Examples of mammals are human, whale, bat etc.

Diversity in Living Organisms NCERT Solutions

Diversity in Living Organisms:NCERT Notes Class 9th

Categories
Class 9 Science

Diversity in Living Organisms:NCERT Notes Class 9th

  • Classification is the Science of arranging organisms in series of groups and subgroups on the basis of their similarities and dissimilarities.
  • Aristotle classified organisms on the basis of their habitat means the place where they live, in water, in air and on land
  • We look for similarities among the organism which allows us to put them into different classes and then study them as a whole.
  • Characteristics are details of appearance or behaviour.
  • The characteristics that decide the broadest divisions among living organisms are independent of any other characteristic in their effects on the form and function of the organism
  • The characteristic in the next level would be independent on the previous one and would decide the variety in the next level.
  • Once a body design comes into existence, it will shape the effects of all subsequent design changes.
  • Characteristics that come into existence are likely to be more basic than characteristics that have come into existence later.
  • Some group of organisms have ancient body designs that have not changed very much and are referred to as primitive or lower organisms.
  • Some group of organisms have acquired their particular body design relatively recently and are referred to as advanced or lower organism.

HIERARCHY OF CLASSIFICATION

  • The kingdoms proposed by whittaker proposed has five kingdoms: Monera, protista, fungi, plantae and animalia.
  • Woese introduced modification by dividing monera into archaebacteria and eubacteria.
  • Classification is done by naming the sub-groups at various levels in the following scheme: kingdom, phylum, class, order, family, genus, species.
  • A species include all organisms that are similar enough to breed and perpetuate.

Further classification is done by naming the subgroups at Various levels as given:
Kingdom→Phyllum\Divison→Class→Order →Family→Genus→Species
•Kingdom Monera
•Kingdom Protista
•Kingdom Fungi
•Kingdom Plantae
•Kingdom Animalia

Monera

  • Organisms in monera kingdom do not have a defined nucleus, organelles or multicellular body design.
  • They may or may not have cell walls
  • The mode of nutrition in organisms of monera kingdom can be autotrophic as well as heterophic.
  • This group includes bacteria, blue-green algae or cyanobacteria, mycoplasma and anabaena.

 

 

Protista

  • Organisms of this group are unicellular, eukaryotic and some of them organisms use appendages, such as hair-like cilia or whip-like flagella for moving around.
  • Examples are unicellular algae, diatoms and protozoans

Fungi

  • Organisms in this group are heterotrophic, eukaryotic and use decaying organic material as food and are therefore called saprophytes.
  • Many of these organisms have the capacity to become multicellular organisms at a certain stages in their lives.
  • They have cell walls made of tough complex sugar called chitin.
  • Yeast, mushrooms, aspergillus, penicillium and agaricus.

  • Some fungal species live in symbiotic relationships, and these life-forms are called lichens.

Plantae

  • The organisms in this group are are multicellular, eukaryotes, autotrophs and use chlorophyll for photosynthesis
  • All plants are included in this group.

Animalia

  • These include all organisms which are multicellular eukaryotes, without cell walls, and are heterotrophs.

PLANTAE

Thallophyta

  • Plants in this group are predominantly aquatic and do not have well-differentiated body design fall in this group.
  • Plants in this are commonly are called algae.
  • Examples of thallophyta are spirogyra, ulothrix, cladophora and chara.

Bryophyta

  • Bryophytes are called the amphibians of the plants.
  • The plants in this group do not have special tissues for conduction of water and other substances from one part of the plant body to another.
  • Examples of bryophyta are moss and marchantia.
  • The plant body is commonly differentiated to form stem and leaf-like structures.

Moss Biodevirsity

Pteridophyta

  • The plant body is differentiated into roots, stem and leaves and has specialised tissue for the conduction of water and other substances from one part of the plant body to another.
  • Plants of pteridophyta are cryptogamae.
  • Cryptogamae are plants with hidden reproductive organs.
  • Phanerogams are plants with well differentiated reproductive tissues that ultimately make seeds.

Gymnosperms

  • The plants of this group bear naked seeds and are usually perennial, evergreen and woody
  • Pines such as deodar are example of gymnosperms

Deodar
Deodar

Angiosperms

  • The seeds of these plants develop inside an organ.
  • These are also called flowering plants.
  • Plant embryos in seeds have cotyledons i.e seed leaves.
  • Monocots are plants with seeds having one cotyledon.
  • Plants with seeds having two cotyledons are called dicots.

Appear the quiz on Biodiversity here

Read the second part of this lesson on Animal Kingdom notes for Class 9th science here

Categories
Class 9 Science

Animal Tissue Classification and Notes Class 9 NCERT

ANIMAL TISSUES

Epithelial tissue

  • The covering or protective tissue in animal body are epithelial tissue, covering most organs and cavities it forms a barrier to keep different body systems separate.
  • The skin, the lining of the mouth, the lining of blood vessels, lung alveoli and kidney tubules are made up of epithelial tissue.
  • Cells of epithelial tissue are tightly packed and form a continuous sheet having small amount of cementing material between them and almost no inter-cellular spaces.
  • All epithelium are separated from the underlying tissue by an extracellular fibrous basement membrane.

Epithelial tissue Classification

i) Squamous epithelial tissue 

  • Squamous epithelial tissue consists of a layer of thin flat cells.
  • It is present in the linings of blood vessels, lungs, mouth, oesophagus etc.
  • The skin has several layers of epithelial cells. This tissue is called Stratified squamous tissue.

ii) Columnar epithelial tissue :-

  • Columnar epithelial tissue consists of tall pillar like cells.
  • It is present in the walls of the intestine.
  • The columnar epithelial tissue in the respiratory tract has hair like projections called cilia.
  • This tissue is called Ciliated columnar epithelial tissue.

iii) Cuboidal epithelial tissue :-

  • Cuboidal epithelial tissue consists of cone shape cells having a basement membrane.
  • It forms the lining of kidney, tubules and ducts of salivary glands and provide mechanical support.

iv) Glandular epithelial tissue :-

  • Sometimes epithelial tissue folds inwards and forms a multicellular gland which secretes substances.
  • This tissue is called Glandular epithelial tissue.

NCERT Solutions Class 9 Science Tissues

Connective tissue

  • The cells of a connective tissue are loosely packed and embedded in inter cellular matrix, this matrix may be jelly like, fluid, dense or rigid.
  • Blood is a type of connective tissue.

i) Blood :-

  • Blood contains a fluid matrix called plasma which contains red blood cells (RBC), white blood cells (WBC) and platelets.
  • The blood transports gases, digested food, hormones, waste materials etc.

ii) Bone :-

  • Bone is a hard and strong tissue
  • It consists of cells which are embedded in a hard matrix containing calcium and phosphorus compounds.
  • Bone forms the framework of the body and supports the body and the main organs.

iii) Ligaments :-

  • Ligaments are flexible tissues which joins bones together and helps in movements.

Ligaments

iv) Tendons :-

  • Tendons are fibrous tissues which joins muscles to bones and helps in movements.

v) Areolar tissues :-

  • It fills the space between skin and muscles, inside the organs, around blood vessels etc.
  • It helps to repair the tissues.

vi) Adipose tissue :-

  • Adipose Tissue is found below the skin and between internal organs.
  • It contains fats and helps to store fats.

Muscular tissue

Muscular Tissue
Muscular Tissue
  • Muscular tissue contains elongated cells are called muscle fibres and is responsible for movement in our body.
  • Muscular tissue contains special proteins called contractile proteins which can contract and relax.
  • Muscles that move by our conscious will are called voluntary muscles for example muscles present in our limbs and are also called skeletal muscles .
  • Muscles which do not move under our will are called involuntary muscles.

i) Striated muscles :-

  • Striated muscles are voluntary muscles having light and dark striations.
  • The cells are long, cylindrical and are multinucleated.
  • They are also called skeletal muscles because they are attached to bones.
  • They help in voluntary movements of the body.

ii) Unstriated muscles ( Smooth muscles) :-

  • Unstriated muscles are involuntary muscles having no striations.
  • The cells are long and spindle shaped and are uninucleated.
  • They are present in alimentary canal, blood vessels, bronchi of lungs, iris of eye etc.
  • They help in involuntary movements.

iii) Cardiac muscles :-

  • Cardiac muscles  are involuntary muscles having faint striations.
  • The cells are long, cylindrical, branched and multinucleated.
  • They are present in the heart and helps in the contraction and relaxation of the heart.

Nervous Tissue

  • Nervous tissue is highly specialized for responding and transmitting stimulus very rapidly.
  • Nervous tissue have cells called neurons containing a cell body with a nucleus and cytoplasm
  • Each neuron has single long part called axon and many short branched part called dendrites.
  • The combination of functions of nerves and muscle tissue is fundamental to animals.

NCERT Solutions Class 9 Science Tissues

Click Here for Quiz on Tissue 

Read the First part of the lesson on Plant Tissue here 

Categories
Class 9 Science

Plant Tissues NCERT Notes for Class 9 Science

What is Tissue

  • Tissue is a group of cells that are similar in structure and/or work together to achieve a particular function.
  • Eg :- In human beings the cells of the muscular tissue contract and relax and help in movements.
  • In plants the cells of the vascular tissue conduct water and food from one part of the plant to the other

Differences between plant and animal tissue

  • Plants do not move from place to place. Most of the cells and tissues in plants provide mechanical support and strength.
  •  Since dead cells do not need maintenance and provide with mechanical support, thus the plant tissues are mainly composed of dead cells
  • The growth of plants takes place only in some regions. So plants have tissues called meristematic tissues which divide and help in growth and permanent tissues which do not divide
  • Animal tissues are composed of mainly living cells.
  • Animals grow uniformly thus there is no such demarcation of dividing and non-dividing regions in animals.
  •  Animals have organs having specialized functions. So the organs have specialized tissues

PLANT TISSUES

Meristematic tissue

  • The growth in plants is limited to specific regions thus the meristematic tissue is located at only these regions
  • The are three types of meristematic tissue apical, lateral and intercalary.
  • When meristematic cells produce new cells the two cells are similar, but as they grow they become differentiated as components of other tissues.
  • Apical meristem is present at the growing tips of stem and roots and increases the length of the stem and root.
  • Intercalary meristem is present at the base of the leaves or internodes on twigs
  • The girth of the stem or root increases due to lateral meristem.
  • Cells of meristematic tissue are very active hence have very dense cytoplasm, this cellulose walls, prominent nuclei and lack vacuoles.

Permanent tissue

  • The cells produced by meristematic tissue take a specific role and loose the ability to divide.
  • Differentiation is the process of taking up a permanent shape, size and function.

Simple permanent tissue

 

  • Parenchyma is a basic packing tissue, consisting of relatively unspecialised cells with thin cell walls.

    parenchyma
    Parenchyma
  • Parenchyma has live cells and are loosely packed.
  • It provides support to plants as well as store food.
  • It stores excretory products such as gums, raisins, tannins and crystals/
  • It may also contain chlorophyll and perform photosynthesis, in such situations it is called collenchyma.
  • In aquatic animals parenchyma contains large air cavities to help them float by giving buoyancy and is called aerenchyma.
  • The parenchyma of stems and roots stores nutrients and water.
  • Collenchyma is a permanent tissue responsible for flexibility in plants along with providing mechanical support and is present in leaf stalks below epidermis.
  • The cells of collenchyma are elongated, irregularly thickened at corners and have very less intercellular space.
  • Sclerenchyma is a permanent tissue which makes plant hard and stiff, and is made up of dead cells, that are long and narrow as the walls are thickened due to lignin.
  • Sclerenchyma is present at veins of leaves, hard covering of seeds and vascular bundles.
  • Coconut husk is made of sclerenchymatous tissue.
  • There are two types of sclerenchyma fibers and sclereids.
  • Sclerenchyma protects plants from the stress and strain of environmental factors like wind.
Epidermal cells
Epidermal cells
  • The outermost layer of cells is called epidermis and is usually made up of single layer of cells and the entire surface of the plant is covered by epidermis.
  • Epidermal cells on the aerial parts of the plant secrete a waxy, water resistant layer on outer surface to aid water loss, mechanical injury and invasion by parasitic fungi.
  • Due to the protective layer that epidermal cells play, they form a continuous layer without intercellular spaces in tissue, are relatively flat and their outer and side walls are thicker than inner wall
stomata
stomata
  • Stomata are pores present in epidermis of tissue enclosed by two kidney shaped cells called guard cells and are responsible for exchanging gases and transpiration.
  • In desert plants epidermal tissue secretes a waxy coating of cutin on its outer surface to prevent loss of water.
  • As plants grow older a strip of secondary meristem replaces the epidermal tissue of the stem and this forms the bark of the tree and cork.

Visit Here for Nitrogen Cycle Explained

cork
cork

Complex permanent tissue

  • Complex permanent tissues are made up of more than one type of cells coordinating to perform a common function
  • Xylem and phloem are a type of complex tissue.
  • They are both conducting tissues and constitute a vascular bundle, which is a feature of complex plants which made their survival possible in terrestrial environment.

Xylem :-

  • Xylem consists of tracheids, vessels, xylem parenchyma and xylem fibres.
  • The tracheids and vessels help to transport water and minerals from roots to all part of the plant.
  • Xylem parenchyma stores food and fibres help in support.
  • Xylem cells have thick walls and are dead.

Phloem :-

  • Phloem Consists of sieve tubes, companion cells, phloem parenchyma and phloem fibres.
  • The sieve tubes and companion cells transports food from leaves to all parts of the plant.
  • Phloem parenchyma stores food and fibres help in support
  • Unlike xylem in phloem, materials can move in both directions.

Appear a quiz on what you have read 

Visit here for the Second Part on Animal Tissue Here 

NCERT Solutions on Tissue

 

Categories
Class 9 Science

The Fundamental unit of life : Cell Structure and Function

Cell Structure and Function

  • Cell is the fundamental and structural unit of life.
  • All living organisms are composed of cells.

  • Amoeba, chlamydomonas, paramoecium and bacteria are unicellular organism.
  • In multicellular organisms, many cell group together to form various body parts and perform different functions.
  • Cells divide to produce cells of their own kind.
  • Amoeba can change their shape.

Structural organisation of Cell

  • Each cell has specific components within it called cell organelles.
  • Cell organelles perform specific functions inside a cell.
  • All cells are found to have the same organelles.
  • Interaction of cell with its environment is possible due to cell organelles.
  • Plasma membrane or cell membrane is the outermost covering of the cell separating the contents of the cell from external environment.

PLASMA MEMBRANE

  • Plasma membrane is selectively permeable.
  • Carbon dioxide and oxygen can move across the cell membrane by diffusion.
  • Diffusion is the process by which substance moves from a region of its high concentration to a region of low concentration
  • Osmosis is the process by which water moves across a selectively permeable membrane from a region of low concentration to a region of low concentration
  • Osmosis is a special type of diffusion.
  • If the medium surrounding the cell has more water concentration then water will move inside the cell and the medium is said to be hypotonic solution.
  • If the medium surrounding the cell and the cell has equal water concentration then water will move inside as well as outside the cell at same rate and thus there will be no net movement of water, such type of a medium is called isotonic solution.

  • If the medium surrounding the cell has less water concentration then the water will move outside the cell and the medium is called hypertonic solution.
  • Cell when placed in a hypertonic solution will swell
  • Cell placed in a isotonic solution will not change its size.
  • Cell placed in a hypertonic solution will shrink.
  • Plant roots absorb water by diffusion.
  • The plasma membrane is flexible and is made up of proteins and lipids.
  • Endocytosis is a process by which amoeba engulfs its food and other material from external environment due to flexibility of plasma membrane.

Animal Cell
Animal Cell

CELL WALL

  • Along with plasma membrane or cell membrane plant cells have another outer rigid covering called the cell wall.
  • The plant cell wall is mainly composed of cellulose.
  • Plasmolysis is the phenomena in which the contents of the cell contract and move away from the cell wall when plant cell looses water due to shrinkage.
  • Cell walls allow cells of plants, fungii and bacteria to withstand very dilute external media without bursting, i.e cell walls can allow cells to withstand much greater changes as compared to the animal cells
Plant cell
Plant cell

NUCLEUS

  • When cells are stained by iodine solution or safranin solution, different parts of the cells get differently coloured according to their chemical composition
  • Nucleus has a double layered covering called nucleus membrane.
  • Transfer of materials from inside of the nucleus to its outside takes place through pores present on nucleus membrane.
  • Nucleus contains chromosomes, which are visible as rod-shaped structures only when the cell is about to divide.
  • Chromosome have DNA ( Deoxyribo Nucleic Acid) molecules which have information of inheritance.
  • DNA is present as a part of chromatin material in a cell which is not dividing.
  • Nucleus plays an important role in cell reproduction and determining the way in which the cell will develop and the form it will exhibit at maturity by directing chemical activities.
  • An poorly defined nuclear region containing only nucleic acid is called nucleoid.
  • Prokaryotes are organisms lacking nucleus membrane.
  • Eukaryotes are organisms having nucleus membrane.
  • Prokaryotic cells also lack other cytoplasmic organelles present in eukaryotic cells.

CYTOPLASM

  • Cytoplasm is the fluid content inside the plasma membrane.
  • Cytoplasm has many specialised cell organelles that perform special functions.
  • Cell organelles also have membranes.
  • Prokaryotes also lack membrane bound cell organelles.
  • Viruses lack any membranes and thus do not show characteristics of life until they enter a living body.

CELL ORGANELLES

  • A cell organelle is a specialized sub-unit within a cell that has a specific function.
  • Organelles are either separately enclosed and may called as membrane-bound organelles or are spatially distinct functional units without a membrane.

Endoplasmic reticulum

  • The endoplasmic reticulum is a large network of membrane-bound tubes and sheets.
  • Endoplasmic reticulum is similar in structure to plasma membrane.
  • There are two types of Endoplasmic reticulum – Rough Endoplasmic Reticulum(RER) and Smooth Endoplasmic Reticulum(SER)
  • Ribosomes attached to the surface of Rough endoplasmic reticulum makes it look rough under a microscope.
  • Ribosomes are site for manufacture of protein.
  • The Smooth Endoplasmic Reticulum helps in manufacture of fat molecules or lipids.
  • Membrane biogenesis is the process by which cell membrane is manufactured using some proteins and lipids.
  • Other proteins and lipids function as enzymes.
  • Endoplasmic reticulum serves as channels for transfer of materials between various regions of the cytoplasm and between cytoplasm and the nucleus.
  • Endoplasmic reticulum also functions as cytoplasmic framework, providing a surface for biochemical activities.
  • Smooth endoplasmic reticulum detoxifies poisons and drugs.

Golgi apparatus

Golgi apparatus
Golgi apparatus
  • Golgi apparatus consists of a system of membrane-bound vesicles arranged approximately parallel to each other in stacks called cristens.
  • The material synthesised at Endoplasmic reticulum is packaged and dispatched to various targets inside and outside the cell through golgi apparatus.
  • Golgi apparatus makes complex sugars from simple sugar.
  • Golgi apparatus is also involved in formation of lysosomes.

Lysosome

  • Lysosome keeps the cell clean by digesting any foreign material as well as worn out cell organelles.
  • Lysosomes contain powering digesting enzymes capable of breaking down all organic material.
  • When the cell gets damaged the lysosomes may burst and the enzymes digest their own cells
  • They are structurally membrane bound sacs filled with digestive enzymes
  • Lysosomes are known as the suicide bag of the cell.
  • The digestive enzyme present in Lysosome is made by Rough Endoplasmic Reticulum.

Mitochondria

  • Mitochondria is the power house of the cell as it produces the energy required for various chemical activities needed for life.
  • Energy released in mitochondria is released in the form of ATP(Adenosine Triphosphate)
  • ATP is the energy currency of the cell.
  • Mitochondria has two membranes, the outer membrane is porous while the inner membrane is deeply folded providing surface for generation of ATP.
  • Mitochondria has its own DNA and ribosome and make their own protein.

Plastids

  • Plastids are present only in plant cells.
  • Leucoplasts are colourless plastids.
  • Chromoplasts are coloured plastids.
  • Plastids containg the pigment chlorophyll is called chloroplasts.
  • Chloroplasts also contains orange and yellow pigment.
  • Leucoplasts are primary organelles in which starch, protein and oil is stored.
  • Plastids contain various membrane layers embedded in a material called storma.
  • Plastids also have their own DNA and ribosome.

Test on Class 9th Biology on Fundamental Unit of Life:CELL

Vacuoles

  • Vacuoles are storage sacs for solid and liquid contents.
  • Vacuoles present in animal cells are smaller as compared to vacuoles present in plant cells.
  • In plant cells vacuoles are full of sap and provide rigidity and turbidity to the cell.
  • Vacuoles store amino acids, sugars and proteins.
  • In some unicellular organisms, specialized vacuoles play important role in expelling excess water and some waste from the cell.

The Fundamental Unit of Life NCERT Solutions

Click Here to Appear The Quiz on the Topic 

Categories
Class 9 Political Science

Preamble Of The Indian Constitution

1. Sovereign
The word ‘sovereign’ implies that India is neither a dependency nor a dominion of any other nation, but an independent state
2. Socialist

Read The Notes on Constitutional Design: Polity Note here 

  • Even before the term was added by the 42nd Amendment in 1976, the Constitution had a socialist content in the form of certain Directive Principles of State Policy.
  • Democratic socialism, on the other hand, holds faith in a ‘mixed economy’ where both public and private sectors co-exist side by side.

3. Secular

  • The term ‘secular’ too was added by the 42nd Constitutional Amendment Act of 1976.
  • all religions in our country (irrespective of their strength) have the same status and support from the state

4. Democratic
A democratic  polity, as stipulated in the Preamble, is based on the doctrine of popular sovereignty, that is, possession of supreme power by the people

5. Republic

  • in our Preamble indicates that India has an elected head called the president.
  • He is elected indirectly for a fixed period of five years.

6. Justice

  • The term ‘justice’ in the Preamble embraces three distinct forms—social, economic and political, secured through various provisions of Fundamental Rights and Directive Principles.

7. Liberty

  • The term ‘liberty’ means the absence of restraints on the activities of individuals, and at the same time, providing opportunities for the development of individual personalities

8. Equality

  • The term ‘equality’ means the absence of special privileges to any section of the society, and the provision of adequate opportunities for all individuals without any discrimination.
  • The Preamble secures to all citizens of India equality of status and opportunity. This provision embraces three dimensions of equality—civic, political and economic.

9. Fraternity

  • Fraternity means a sense of brotherhood.
  • The Constitution promotes this feeling of fraternity by the system of single citizenship.

 

Categories
Class 9 Political Science

Constitutional Design: Polity Note for Class 9th NCERT

Constitution

  • All such certain basic rules that the citizens and the government have to follow together are called constitution.
  • As the supreme law of the country, the constitution determines the rights of citizens, the powers of the government and how the government should function.

WHY DO WE NEED A CONSTITUTION?

Constitution is the supreme law that determines the relationship among people living in a territory (called citizens) and also the relationship between the people and government.

  • it generates a degree of trust and coordination that is necessary for different kind of people to live together
  •  it specifies how the government will be constituted, who will have power to take which
    decisions
  •  It lays down limits on the powers of the government and tells us what the rights of the citizens are
  •  It expresses the aspirations of the people about creating a good society.

MAKING OF THE INDIAN CONSTITUTION

Challenges in making the Indian constitution

  • The size and diversity of India was a huge challenge
  • The issue of partition and religious difference
  • Indian were so called subjects in British time and were to become citizens of India
  • The merger of the princely states as Britishers had left it to the rulers of the princely states to decide whether they wanted to merge with India or with Pakistan or remain independent
  • There were anxieties about the present and the future of the country

Despite all such issues it was not a challenge to decide how the Independent India should look like as

  • Much of this consensus had evolved during the freedom struggle.
  • Our national movement was not merely a struggle against a foreign rule.
  • It was also a struggle to rejuvenate our country and to transform our society and politics

in 1928, Motilal Nehru and eight other Congress leaders and In 1931, the resolution at the Karachi session of the Indian National Congress dwelt on how independent India’s constitution should look like.

Both these documents were committed to the inclusion of universal adult franchise, right to freedom and equality and to protecting the rights of minorities in the constitution of independent India

The limited franchise based election of the year 1922 and 1937 had provided experience
to Indians in the working of the legislative institutions
This experince proved to be very useful for the country in setting up its own institutions

Features borrowed in Indian Constitution from other countries 

  • We borrowed many features from other democratic countries of that time
  •  Yet they were not simply imitating what others had done.
  • At each step they were questioning whether these things suited our country.

All these factors contributed to the making of our Constitution.

Who framed the Constitution of India

  • The Constitution of India framed by Constitution Constituent Assembly which was established in 1946.
  • Elections to the Constituent Assembly were held in July 1946.
  • Its first meeting was held in December 1946.
  • Constituent Assembly was to be a partly elected and partly nominated body.
  • Moreover, the members were to be indirectly elected by the members of the provincial assemblies, who themselves were elected on a limited franchise
  • Soon after, the country divided into India and Pakistan.
  • The Constituent Assembly was also divided into the Constituent Assembly of India and that of Pakistan.
  • The Constituent Assembly that wrote the Indian constitution had 299 members.
  • The Assembly adopted the Constitution on 26 November 1949 but it came into effect on 26 January 1950.
  • To mark this day we celebrate January 26 as Republic Day every year.

Criticism of Constituent Assembly

1. Not a Representative Body: The critics have argued that the Constituent Assembly was not a representative body as its members were not directly elected by the people of India on the basis of universal adult franchise.
2.
Not a Sovereign Body: The critics maintained that the Constituent Assembly was not a
sovereign body as it was created by the proposals of the British Government. Further, they
said that the Assembly held its sessions with the permission of the British Government.
3.
Time Consuming: According to the critics, the Constituent Assembly took unduly long time to make the Constitution. They stated that the framers of the American Constitution took only four months to complete their work.
4.
Dominated by Congress: The critics charged that the Constituent Assembly was dominated by the Congress party. 
5.
Lawyer–Politician Domination: It is also maintained by the critics that the Constituent Assembly was dominated by lawyers and politicians. They pointed out that other sections of the society were not sufficiently represented. This, to them, is the main reason for the bulkiness and complicated language of the Constitution.
6.
Dominated by Hindus: According to some critics, the Constituent Assembly was a Hindu dominated body. 

 Values  embedded in the Preamble of the Indian Constitution.

  • They guide all the articles of the Indian Constitution.
  • The Constitution begins with a short statement of its basic values.
  • This is called the Preamble to the constitution.
  • Taking inspiration from American model, most countries in the contemporary
    world have chosen to begin their constitutions with a preamble
  • Source of authority of the Constitution: The Preamble states that the Constitution derives its authority from the people of India
  • Nature of Indian State: It declares India to be of a sovereign, socialist, secular democratic and republican polity.
  • Objectives of the Constitution: It specifies justice, liberty, equality and fraternity as the objectives.

What is democracy ? Why Democracy Notes on NCERT For Class 9th

Read more about the Preamble here 

Categories
Class 9 Political Science

What is democracy ? Why Democracy Notes on NCERT For Class 9th

  • Democracy –  Democracy has been derived from two Greek word  demos and cratia.
  • Demos means ‘ the people’ and cratia means ‘power’
  • Democracy is a form of government which the administration of the country is run by the representatives who are elected by the people.

Features of democracy

  • Rulers elected by the people take all the major decisions
  • Elections offer a choice and fair opportunity to the people to change the current rulers
  • This choice and opportunity is available to all the people on an equal basis
  • The exercise of this choice leads to a government limited by basic rules of the constitution and citizens’ rights

Direct democracy

  • it is that form of government in which people directly participate in the affairs of the State.
  • in this system the public opinion is expressed directly in assemblies meetings.
  • All the adult citizens have the right to participate in  public meetings of the assembly where all the laws are passed, taxes are assessed etc.
  • This type of system is only possible where the population is small and it is possible for all the citizen to participate directly in the affairs of the state, nowadays this system exists only in a few cantons of Switzerland and some states in USA

indirect democracy

  • indirect democracy are much larger countries.
  • Under this system people elect their representative for a period who run the administration .
  • if they don’t work according to the wishes of the people and for their welfare , they are hanged  till the time of next election
  • People don’t take part directly in the affair of the state.
  • Examples of few democratic countries in the world are India ,USA ,England ,SriLanka.

Dictatorship –

  • it is a form of government in which all the power are concentrated in the hands of a single person or a party of which he is the leader.
  • He is not answerable to any body and nobody can oppose him.
  • Italy and Germany before the second world war had this form of government

Is Democracy suitable to all the Nations

  • Some people has an opinion that democracy is suitable only to those countries
    which are ‘‘industrialized and economically developed
  • They are of the opinion that democracy may not be suitable for countries like India Pakistan etc.
  • They argue that faster and better development is possible only in dictatorship where there is discipline among citizens and no time is wasted in the process of passing a legislature .
  • But this is not true. We have democracies (like India, England and U.S.A.) performing much better for the removal of poverty and backwardness in their respective countries.
  • In India, government has implemented several schemes for the welfare of the people and implemented policies to ensure equal opportunities for all the citizens in the fields of education and employment.
  • On the other hand, under dictatorship, the dictators do not take much interest in the economic development of the country.
  • Only’those in power and supporters of the ruling group enjoy all the benefits and privileges.
  • They amass wealth through illegal and corrupt means.
  • Thus, democracy is suitable for all the nation.

Five merits of democracy

Taking the example of china , when in 1958-61 , many people died because of large famine . The economic condition of India was also not in a good state those days , yet we were able to avoid such large scale famine because we had democracy.

  1. Democracy is based on the principle of equality-
  • All the members or the state are equal in the eyes of law.
  • All enjoy equal social, political and economic benefits and state cannot discriminate among the citizens on the basis of caste,religion,sex,or property

2. Stability and responsibility in administration

  • The tenure of the elected representatives is fixed, They form a stable  government

3. It is more accountable to people

  • A nondemocratic government may and can respond to the people’s needs, but it
    all depends on the wishes of the people who rule.
  • If the rulers don’t want to, they don’t have to act according to the wishes of the people.
  • A democracy requires that the rulers have to attend to the needs of the people

4. Democracy improves the quality of decision-making

  • Democracy is based on consultation and discussion.
  • A democratic decision always involves many persons, discussions and meetings.
  • Although this takes time but it allows to find out the mistakes .
  • But there is a big advantage in taking time over important decisions.
  • This reduces the chances of rash or irresponsible decisions.

5. Democracy provides a method to deal with differences and conflicts

  • people are bound to have differences of opinions and interests.
  • These differences are particularly sharp in a country like ours which has an amazing social diversity.
  • People belong to different regions, speak different languages, practise different religions and have different castes.
  • They look at the world very differently and have different preferences.
  • The preferences of one group can clash with those of other groups.
  • Democracy provides the only peaceful solution to this problem.
  • In democracy, no one is a permanent winner. No one is a permanent loser.
  • Different groups can live with one another peacefully.

6. Democracy allows us to correct its own mistakes.

  •  There is no guarantee that mistakes cannot be made in democracy.
  • No form of government can guarantee that.
  • The advantage in a democracy is that such mistakes cannot be hidden for long.
  • There is a space for public discussion on these mistakes.
  • There is a room for correction.
  • Either the rulers have to change their decisions, or the rulers can be changed.

Arguments against democracy

  • Leaders keep changing in a democracy.
  • This leads to instability.
  • Democracy is all about political competition and power play.
  • There is no scope for morality.
  • So many people have to be consulted in a democracy that it leads to delays.
  • Elected leaders do not know the best interest of the people.
  • It leads to bad decisions.
  • Democracy leads to corruption for it is based on electoral competition.
  • Ordinary people don’t know what is good for them; they should not decide anything.

Challenges to democracy

  • Growing economic and social inequalities among the people
  • Although all the citizens have the right to vote and fight elections rich people have a chance to win the election.
  • The poor are sometimes even forced to sell their votes to fulfill their basic necessities of life like food, clothing and shelter
  • So rich people are elected representatives in the legislature who make laws and frame policies which favour them
  • Role of anti-social elements –
  • The role of anti-social elements has increased very much during the elections.
  • Voters are coerced to vote for a particular candidate or party.
  • Rigging also takes place during the elections.
  •  During elections, a large number of voters give weight to the caste and religion of the candidate-
  • Political parties also keep in mind  the caste or religion of a person while distributing tickets for the election
  • Representatives also work for the favor of people on the basis of caste or religion

Remedies for the removal of drawbacks of democracy.

  1. Efforts should be made to reduce the social and economic inequalities among the
    citizens.
  2.  People should be educated.
  3. Only educated people can realize the importance of the right to vote and other political rights
  4. Use of caste and religion should be banned.
  5. Organisation of political parties on the basis  religion should be checked.
  6. Candidates making use of caste or religion should be disqualified
  7. democratic values should be cultivated in families

Constitutional Design: Polity Note for Class 9th NCERT