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Class 10th Science

Heredity And Evolution : Class 10 Notes on NCERT

ACCUMULATION OF VARIATION DURING REPRODUCTION

  • Heredity :- The process of transfer of characters or traits from the parents to their offsprings is called heredity.
  • Variations :- The differences between the characters or traits among the individuals of the same species are called variations.
  • For example human height is a trait which shows different variations like tall, short, medium etc.

  • Another example is earlobe, it shows two variations free earlobe and attached earlobe.
  • The variation is necessary for evolution The great advantage of variation is that it increases the chance of survival in a changing environment

Accumulation of variations during reproduction

  • The reproduction produces variations in offsprings .
  • The  minor variations are seen  due to inaccuracies in DNA copying.
  • These variations are less in asexual reproduction and more in sexual reproduction.
  • Some variations are useful variations and they help the organism to adjust to the changes in the environment.
  • Some variations do not help the organism to adjust to the changes in the environment and they may die and become extinct

Transfer of characters

  • Characters are transferred through DNA molecules present in the gene on the chromosomes which are present in the nucleus of the cell.
  • The inheritance of characters is due to the fact that both the father and mother contributes equal amount of genetic material to the child.
  • So for each trait there are two factors one from the father and one from the mother
The structure of the chromosome

CHROMOSOME: A thread like structure in the nucleus of cell formed of DNA and protein
which carries the genes.
GENE: A unit of DNA or a segment of DNA which controls specific characteristic of an
organism.
ALLELES: They are various forms of a gene which occur at the same particular position or
locus over the chromosomes.
DOMINANT GENE: The gene which decide the expression of a character even in the presence of an alternative gene.
RECESSIVE GENE: The gene which decides the expression of an organism in the presence of another identical gene.

  • The dominant gene is represented by a capital letter and the corresponding recessive gene is represented by the same letter in small.
  • For example the dominant gene for tallness is represented by T and the recessive gene for dwarfness is represented by t.
  • Genotype:-  The genotype is the description of genes present in an organism.
  • Phenotype:- The characteristic or trait which is visible in an organism Is called phenotype. Ex- Tall or dwarf.

Rules for the Inheritance of Traits – Mendel’s Contributions

Mono-Hybrid Crossing 

  • Gregor Johann Mendel conducted experiments with garden pea plants and determined the rules for the inheritance of traits
  • Mendel selected pea plants having one pair of character – a tall pea plant and a
    short pea plant.
  • He selected pure tall (TT) and pure short (tt) pea plants and cross pollinated them.
  • He obtained all tall plants (Tt) in the first generation (F1 )
  • When the first generation plants were self pollinated, he obtained tall and dwarf
    plants in the ratio 3:1 in the second generation. (F2)
  • The ratio of pure tall (TT), hybrid tall (Tt) and pure dwarf (tt) was in the ratio 1:2:1
  • The trait that is expressed in the F1 generation is called the dominant trait and the trait that is suppressed in the F1 is called the recessive trait.

Dihybrid cross

  • When plants having two pairs of characters (Eg:- shape and colour of seeds) were crossed (Dihybrid cross)
  • Mendel selected pea plants having two pairs of characters – shape and colour
    of seed.
  • He selected plants having round yellow seeds (RRYY) and wrinkled green seeds (rryy) and cross pollinated them.
  • He obtained all plants with round yellow seeds (RrYy) in the F1 generation.
  • When these plants were self pollinated in the F2 generation out of 16 plants, 9 had round yellow (RrYy), 3 had round green (Rryy), 3 had wrinkled yellow (rrYy) and 1 had wrinkled green (rryy) seed  In the ratio 9:3:3:1.Heredity and Evolution NCERT Solutions For Class 10th SCIENCE
Categories
Class 10th Science

Sexual Reproduction in Human Beings : Study Notes for Class 10th Science

Reproduction in human beings

  • Puberty-it is the period during which adolescents reach sexual maturity and become capable of reproduction
  • During early teenage whole new set of changes occurs, appearance of body and proportions change and new features develop.
  • As the rate of general body growth slows down reproductive tissues begin to mature.
  • If animals are to participate in the process of mating, their state of sexual maturity must be identifiable by other individuals.
Pubertal changes in males Pubertal changes in females
a) deepening of voice(low pitch)
b) broadening of shoulders
c) appearance of beard & moustaches
d) Growth of axillary & pubic hairs
a) high pitch voice
b) widening of hips
c) Growth of axillary & pubic hairs
d) Initiation of menstruation
e) Growth of mammary glands.

Male reproductive system

Male reproductive system
Male reproductive system

1. Testis:

  • Testis is a galndular organ made up of fine tubules.
  • The formation of germ cells take place in testes, located outside the abdominal cavity in scrotum because sperm formation requires a lower body temperature.
  • testis also produces certain hormones, like tetosterone which are responsible for secondary sexual characters in humans.
  • These are deep male voice, hair growth in pubic area and under armpits, and facial hair.

2. Seminal Vesicle: Once sperm is produced it is stored in seminal vesicle.

3. Vas Deferens:

  • Vas deference is the tube through which semen containing sperm is transferred out.
  • The sperms produced are transferred by vas deferens which unites with a tube coming from urinary bladder.
  • Urethra forms a common passage for both sperm and urine.
  • To make the transportation of sperms easier prostate and seminal vesicles add their seceretions along the path of vas deferens, that makes the sperms to be transported in fluid which provides nutrition.
  • Cowper‘s gland – Produces white viscous & alkaline secretion
  • Semen = sperm& secretion of accessory glands

Female Reproductive system

1. Ovary:

  • Ovaries are situated on left and right side of the uterus.
  • The female germ-cells are produced in ovary, which is also responsible for production of oestrogen.
  • On reaching puberty some of the immature eggs present in the ovary of a girl start maturing.

2. Fallopian Tubes:

  • Fallopian tubes extends on both sides of the uterus in transverse direction.
  • Fallopian tubes have finger like structures which catch the eggs to transfer them to the uterus.

3. Uterus:

  • Uterus is a bag like structure, with an opening in the vagina.
  • Uterus opens into the vagina through cervix.

Fertilization In Human Beings 

  • Sperms enter through the vaginal passage during sexual intercourse and encounters egg in fallopian tube.
  • Once eggs reach uterus, a layer of soft tissues develops to support the embryo.
  • This layer is called corpus luteum.
  • If fertilization takes place, then the embryo develops into a foetus and ultimately to a fully developed child over a period of about 9 months
  • The zygote gets implanted into the lining of the uterus and starts dividing.
  • The uterus prepares itself every month to receive and nurture the the embryo, the lining thickens and is richly supplied with blood to nourish the growing embryo.
  • The embryo gets nutrition from the mother’s blood with the help of a tissue called placenta, a disc embedded in uterine wall.
  • The child is born as a result of rhythmic contractions of the muscles of uterus.
Female reproductive system
Female reproductive system
  • Implantation : Attachment of embryo to the lining of uterus.
  • Placenta : A connection between the mother & the foetus
  • The foetus meets all its developmental needs such as nutrition, respiration and excretion through the placenta.
  • Gestation period :The period between fertilisation & birth

Menstrual Cycle in Females:

  • If no fertilization takes place then after about two weeks the dead eggs and corpus luteum gets expelled out of the uterus through vagina.
  • This process takes place over a period of about three to four days.
  • This clears the way for new batch of eggs to come in the uterus.
  • The whole cycle from egg production to the expulsion of eggs takes about four weeks.
  • This cycle is known as Menstrual Cycle.
  • Apart from humans, some primates like Chimpanzee and Gorilla also show same
    phenomenon.
  • Ovary secretes one of the important hormones estrogen, which is responsible for secondary sexual characters in female, like thin voice and breast enlargement.

Menarche – commencement of menstrual cycle at puberty which marks the beginning of reproductive life of the human female.

Menopause – cessation of menstrual cycle which marks the end of the  reproductive life of a human female.

Reproductive Health and Birth Control Methods 

  • Creation of a mechanical barrier is a method of contraceptive so that the sperm does not reach the egg is called condoms.
  • Oral pills change the hormonal balance of the body
  • Loops and copper-T is placed in the uterus to prevent pregnancy
  • Surgical method can be used to block vas deferens in male and fallopian tube in female.

Read Here on Sexual Reproduction In Plants(Second Part of the Lesson) 

Previously Asked Questions on Reproduction in Human beings 

  1. How does the male gamete reach the egg present in the ovary?
    The pollen tube releases the male gametes in the embryo sac .
  2. What are gonads?
    Gonads are the primary sex organs which produce gametes & secrete sex
    hormones.
  3.  Define syngamy.
    The process of fusion of male gamete with the female gamete is known as syngamy.
  4.  At what age human males attain puberty?
    At the age of 12-14 years
  5.  At what age human females attain puberty?
    At the age of 10-12 years.
  6.  What are the functions of gonads?
    i) production of gametes
    ii) secretion of sex hormones.
  7. Why are testes located outside the abdominal cavity ?
    Sperm formation requires a temperature lower than that of the normal body temperature.
  8.  Where are ovaries located in human females?
    Ovaries are present in the abdominal cavity near the kidneys.
  9. What is placenta?
    A connection between the mother & the foetus.The foetus meets it all its developmental needs such as nutrition, respiration and excretion through the placenta.
  10. What is menstruation?
    If fertilization does not occur the uterine wall slowly breaks & comes out through vagina as blood and mucous.
  11. What is ovulation?
    It is the process of release of a mature ovum from the ovary.
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

 

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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.

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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