Reproduction

        

 

      

How do Organisms Reproduce?

 

💠 Life Span

 ▪️The time period between birth to 

      natural death of an organism is called 

      life span. 

 ▪️E.g. Humans: 60 - 70 years

              Turtle: 100 - 120 years

              Mango tree: 200 years

              Banyan tree: 400 - 500 years

              Peepal tree: 2000 - 2500 years etc.

💠 Reproduction

 ▪️It is the process of creation of new 

      organisms from existing ones. 

 ▪️Biological phenomena by which 

      organisms produce more of its own 

      kind is called reproduction.        

 ▪️It involves the transmission of genetic

      material from the parental generation 

      to the next generation.    

 ▪️It introduces variability. 

 ▪️The continuity of life on Earth from its 

      origin to the present day, has been 

      possible only because of reproduction.

🔆 Importance of Reproduction

 ▪️It is essential for the survival of a 

      species on this Earth. 

 ▪️It maintains the continuity of life on 

      Earth. 

 ▪️It gives rise to more Organisms with 

     the same basic characteristics as their 

     parents. 

☮️ Modes of Reproduction

 ▪️There are two modes of reproduction:

  1. Asexual reproduction

  2. Sexual reproduction

1. Asexual Reproduction

▪️A + sexual 

     A means absence and sexual means 

    sexcell

  ▪️A mode of reproduction in which new

      organisms are formed from single 

      parent without involvement of sex cell 

      is called asexual reproduction.

 ▪️No gametes are formed in this 

      process.

 ▪️It is a rapid mode of multiplication. 

 ▪️New individuals produced are 

     genetically identical to the parents.

 ▪️Only one Organism is involved , 

     different sexes are not involved. 

☮️ Types of Asexual Reproduction

 ▪️It is of six types:

 a. Fission

 b. Budding

 c. Fragmentation

 d. Spore formation

 e. Regeneration

 f. Vagetative Propagation

a. Fission

▪️The process of spiliting of parent body 

     into two equal halves  is called fission. 

 ▪️On the basis of spiliting body, fission is

    of two types:

   Binary fission and Multiple fission

♒ Binary Fission

 ▪️Fission, in which two individuals are 

     formed from a single parent, is called 

     binary fission. 

 ▪️E.g. Amoeba, Paramoecium, Bacteria, 

     Leishmania, yeast and etc. 

 ▪️Diagram 👇 

♍ Multiple Fission

 ▪️Fission in which many individuals are 

     formed from a single parent, is called

     Multiple Fission.

 ▪️This type of reproduction occurs in 

     unfavourable conditions.

 ▪️The unicellular organism develops a 

      protective covering over the cell is 

     called cyst.

 ▪️When conditions are favourable the

      Cyst breaks and small offsprings are 

      liberated.

 ▪️E.g. Plasmodium and Monocystis, etc. 

 ▪️Diagram👇

b. Budding

▪️A mode of asexual reproduction in 

    which new organisms are produced 

   from bud of parent organisms is called 

   budding.

▪️E.g. Hydra, Yeast and etc. 

▪️Diagram  👇

                                   &

 

c. Fragmentation

▪️The breaking up of the of Organism 

     into pieces/fragments on maturing is 

     called fragmentation. 

▪️It occurs in simple multicellular plants

     as well as animals.

▪️E.g. Spirogyra (algae), Sea anemone (animal), etc. 

▪️Diagram 👇

d. Spore Formation

▪️A mode of asexual reproduction in 

     which new organisms are formed from 

    spores is called spore formation.

▪️Spores are the microscopic asexual 

     reproductive unit. 

▪️Spores/zoospores are protected by a 

    hard coat known as sporangia(singular: 

    sporangium).

▪️E.g. Penicillium, mosses, Ferns, etc. 

▪️Diagram 👇

   

&

e. Regeneration

▪️The process of getting back a full 

    organism from the body parts of parent 

    individual is called regeneration.

▪️It is the ability of an organism to 

     replace its lost body part. This ability

     to regenerate is due to presence of

    stem cells.

▪️Higher animals have limited power of 

    regeneration (tail in wall lizard, arm in 

    starfish).

▪️E.g. Planaria, Hydra, etc. 

▪️Diagram 👇 

  

f. Vegetative Propagation

▪️A mode of asexual reproduction in 

    which new plants are obtained from the

    parts of old plant without the help of 

    reproductive organs is called vegetative

   propagation.

▪️Vegetative parts like roots, shoot and 

    leaves are used to generate/form new 

   Organisms. 

▪️ It is of two types:

  i. Natural Vegetative propagation

 ii. Artificial Vegetative propagation

(i) Natural Vegetative Propagation

▪️A type of vegetative propagation in 

    which plant reproduce without the

    help of human being is called natural 

    vegetative propagation.

✳️By Leaves: leaves of some plants 

    produce adventitious buds on their 

    margin. This buds develop into new 

    plants. 

 ▪️E.g. Bryophyllum, Kalanchoe, etc. 

❇️ By Stem : In many plant, underground 

      stem produce aerial suits annually 

      under favourable conditions.

▪️ E.g. Potato, Ginger, Onion, Sugarcane,

      China rose, etc. 

❇️ By Roots : roots produce adventitious 

      buds which develops into new plants.

▪️E.g. Sweet potato, Turnip, etc. 

(ii) Artificial Vegetative Propagation

 ▪️The process of growing many plants

      from one plant by man made method 

      is called artificial vegetative 

      propagation.

▪️These are of four types:

☯️ Cutting

 ▪️In this method a small part of plant is 

      cut and buried partially in the moist 

      soil then cutting develops roots and 

      grows into a new plant.

 ▪️E.g. Rose(stem), Lemon(roots), 

      Begonia(leaves), Sugarcane, Cactus, 

      , etc. 

☯️ Layering

 ▪️In this method a branch of parent plant 

      is buried in the soil. The portion of the 

      branch which is in contact with the 

      soil produces roots and this rooted 

      branch is called layer. 

 ▪️E.g. Jasmine, Bougainvillea, etc. 

☯️ Grafting

 ▪️A method in which the cut stem of two 

     different plants are joined together in

     such a way that two stems join and 

     grow as a single plant is known as 

     grafting.

 ▪️Grafting is not possible in monocot 

      plants because cambium activity is 

      absent.

 ▪️E.g. Mango, Apple, Lemon, etc. 

[ Note: 

  a. Stock : The cut stem of a plant having 

      root is called stock.

  b. Scion : The cut stem of another plant 

      without root is called Scion. ]

   Diagram 👇

❇️Tissue culture 

 ▪️ It is also known as micropropagation 

      because a large number of plants are 

      formed from a small tissue.

 ▪️Disease free plants are produced by 

      micropropagation. Cells or tissue 

      which is isolated from the growing of 

      plant called explant.

 ▪️The explant develops into 

      undifferentiated mass of cells called 

      callus in the proper culture medium. 

 ▪️The callus is transferred to another 

      medium containing hormones for 

     growth and differentiation, that forms 

     plantlet.

 ▪️Then the plantlets are transplanted 

     into pot or soil to form mature plant 

     and this technique is known as tissue 

     culture.

 ▪️E.g. Orchids, Chrysanthemum, etc. 

  .   Diagram👇  

🔆 Advantages of Vegetative 

 ▪️The plants which do not produce 

      viable seeds or produce very few 

      seeds can be propagated by this 

      method. E.g. Banana, potato 

      sugarcane, grape orange etc.

▪️ The plants raised by vegetative 

      propagation bear flowers and fruits

      earlier than those produced from

      seeds.

▪️ It is a cheaper and more rapid method

     of plant propagation than growing 

      plants from seeds.

▪️ Seedless fruits like seedless oranges 

      and grapes can be obtained by this 

     method. etc. 

🌞 Advantages of Asexual Reproduction

 ▪️ It is only method of reproduction in 

       most unicellular organisms.

 ▪️ The parental properties are preserved.

 ▪️ It is a rapid method and only one 

       individual is enough for this process.

 ▪️It does not require any sexual 

      maturation, production of gametes,

      transfer of gamete and their fusion.

2 . Sexual Reproduction

🔸A mode of reproduction in which new 

     organisms are formed by the fusion of 

     two different gametes is called sexual         reproduction.  

🔸It is a complex but slow process. 

🔸It introducess Variability. 

🔆 Events in Sexual Reproduction

🔸Mainly three events occur in sexual 

     reproduction:

1. Pre- Fertilization Event

▪️It includes: 

                       Gametogenesis &

                      Gamete transfer

i) Gametogenesis

▪️ The process of formation of gametes 

      is called gametogenesis.

▪️It takes place in both(make & female). 

▪️Gametogenesis is known as 

     spermatogenesis in males whereas

     Oogenesis in females. 

▪️Gametes are the reproductive unit or

     sex cells. 

▪️Gametes are of two types:

   a. Isogametes : Gametes having similar 

       structure and shape are called 

       isogametes. 

▪️E.g. Chlamydomonas, Besidiomycota, 

        Cladophora, etc.

     

   b. Heterogametes: Gametes which do 

       not have similar structure are called 

       heterogametes. 

▪️E.g. Humans, animals, etc. 

ii). Gamete transfer

▪️The process of bringing of compatible 

     gametes near each other is called 

     gamete transfer.

2. Fertilization

▪️It is also known as syngamy.

▪️The process of fusion of male and 

     female gametes is called fertilization.

▪️Site of fertilization is different in 

     different organisms ( It may occurs 

     inside or outside to the female body). 

🌞 Types of Fertilization

 ▪️ Fertilization can be of two types:

   a. External Fertilization: The fertilization

       which occurs outside the body of 

       organisms is called external

       fertilization.

 ▪️E.g. Frogs, Fishes & etc. 

 ▪️The chances of fertilization is very 

      poor and more gametes are produced

      in this mode of Fertilization. 

  b. Internal fertilization:

 ▪️The fertilization which occurs inside 

      the body of the organisms is called 

      internal fertilization.

 ▪️Chances of fertilization is more and 

      less gametes are produced. 

 ▪️E.g. Humans, animals like dog, cow, 

     elephant ,etc. 

3. Post Fertilization Event

▪️It includes: 

                     Formation of Zygote & 

                     Embryogenesis. 

a. Zygote

▪️The cell which is formed after the 

     fusion of male and female gametes is 

     known as Zygote (2n).

▪️It undergoes in many stages and form 

    embryo. 

b. Embryogenesis

▪️The process of formation of embryo

     from zygote is called embryogenesis.

Note:

🔆 Phases in Life Cycle

 ▪️There are mainly three phases in the 

      life cycle of an individual:

a. Juvenile Phase: The pre-reproductive

    period in the life cycle of an individual

    Or organism is called juvenile phase.

 ▪️It varies organism to Organism. 

 ▪️It is known as vagetative phase in 

      plants. 

b. Reproductive phase: The phase of life 

    cycle wherein individuals have the 

    potential to reproduce is called

    reproductive phase or maturity. 

c. Senescent phase: It is the end of the 

    reproductive phase or beginning of the

    post-reproductive phase. 

▪️Chances of catching diseases become

     more in this phase. 

🔆 Reproduction in Flowering Plants

  ▪️Sexual reproduction occurs in 

       flowering plants. 

  ▪️Flower: It is the modification of 

       shoot.

  ▪️Types of flower -2

  1.Unisexual flowers: The flowers which 

      have either male or female part are 

      called unisexual flowers. 

  E.g. Coconut, Papaya, Watermelon, etc. 

2. Bisexual flowers: Those flowers which

   have both i.e male and female part are 

    called bisexual flowers. 

  E.g. Lily, Sunflower, Mustard, etc. 

🔆 Parts of Flower

 ▪️ A flower generally bears a stalk or 

      Pedicel and Thalamus and a Typical  

      flower has Four whorls:

 ▪️Calyx - Group of sepals. 

 ▪️Corolla - Group of petals. 

 ▪️Androecium( male part) - Group of 

      stamens  & 

 ▪️Gynoecium ( female part) - Group of 

      Carpels/ Pistils. 

▪️ Androecium and gynoecium are the

      reproductive parts of the flower.

▪️The outermost whorls like a calyx and 

     corolla do not directly take part in 

     reproduction and hence are called 

    Accessory or non- essential whorls. 

1. Calyx

🔹It is the outermost whorl consisting

    sepals. Sepals are green and leaf like 

    structure. 

🔹It protect the flower bud before it 

    opens. 

 2. Corolla

🔹It is the second whorl, inner to calyx, 

     consisting of petals. Petals are 

     generally large, coloured and showy. 

🔹It attract insects for pollination. 

3. Androecium

🔹It is the third whorl, inner to corolla, 

    consisting of male reproductive parts

    called stamens. 

🔹Each stamen has two parts : Filament 

    & Anther. 

🔹Anther is biloned structure present at 

     the tip of filament. Each anther has 

     pollen sacs(microsporangium) which 

     contain pollen grains(mucrospore). 

🔹Each pollen grain producess two 

     male gametes/germ cells. 

4. Gynoecium

🔹It is the fourth and innermost whorl 

    consisting of carpels. They are 

    present in the centre of flower. 

🔹Each carpel has three parts: Ovary, 

     Style and Stigma. 

🔹Ovary is a swollen basal part of 

     carpel. It contains ovules which are 

     attached to placenta. 

🔹Each ovule contain an embryosac

     that bears haploid egg(female 

     gamete). 

🔹Style is the middle part of the carpel. 

     It has stigma above it and ovary below

     it.

🔹Stigma is the apical part of carpel. It 

     receives pollen grains. 

🔆 Diagram of flower👇

     

Note;

[ Placentation : The arrangement of 

  ovules in the ovary os called 

  placentation ]. 

💠 Pollination

🔹The landing of pollen grains from the 

     anther to the stigma is called 

     pollination. 

🔅Types : 2

   1. Self pollination  

   2. Cross pollination

1. Self Pollination

🔹The transfer of  pollen grains from 

     anther to the stigma of the same plant

     is called self pollination.

🔸It is also known as autogamy.

🔸If it is between flowers of the same

     plant then it is called self pollination.

🔸It generally takes place in bisexual 

    flowers.

E.g. Pea

🌞 Advantages :

▪️Self pollination is easy and most likely

     to occur as the stamen and carpels 

     mature at the same time.

▪️It preserves the parental characters 

     indefinitely because the gametes of the

     same flower of the same plants are 

     involved.

▪️Small quantity of pollen is sufficient, 

     thus, it is economical.

▪️The flowers need not to produce

     nectar and scent and they need not to 

     be showy.

2. Cross pollination

🔸The transfer of pollen grains from 

     anther to the stigma of different plants 

     of the same species is called cross 

     pollination.

E.g. Mango

🌞 Advantages :

▪️Cross pollination is a source of 

     variation in offsprings because of 

     intermixing of genetic make-up of two

     plants.

▪️The seeds produced are viable and 

     healthier and have better germination

    capacity.

♓ Differences between Self pollination & 

     Cross pollination 👇👇

🔆 Agencies of pollination/Pollinator

▪️The transfer of pollen from one flower

     to another is achieved by agents like 

     wind, water animals insect and birds, 

    called Pollinators.

Flowchart : 👇👇 

🔆 Fertilization (In plants)

▪️The process of fusion of the male and 

     female gametes is called fertilization.

▪️It takes place in the embryo sac present

     in the ovule.

Process of Fertilization : 

▪️After pollination pollen grains 

    germinate on the stigma by producing 

    pollen tube, the nucleus in the pollen 

    tube divides into two male gametes.

◾Pollen tube penetrates the stigma and

     passes through the style and enters

    the ovule through micropyle. It 

    releases two male gametes  in

    embryo sac.

▪️One male gamete fuses with egg cell 

    and second male gamete fuses with 

    the two polar nuclei.

🔹 One male gamete(1n) + Egg cell (1n) 

                                  ↓ syngamy

                            Zygote (2n) 

🔹Second male gamete (1n) + Two 

                    polar nuclei (2n) 

                             ↓ triple fusion

                  Endosperm (3n) 

🔹Syngamy + Triple fusion= Double 

     fertilization. 

🔅Post fertilization changes in the 

     flower :

🔹Sepals, petals and stamen withers 

     off. 

🔹Style and stigma degenerates. 

🔹Ovary develops into fruit and ovule 

    grows into seed. 

🔹The seed contains the future plant or 

     embryo which develops into a 

   seedling under appropriate conditions. 

Note:

[ Dormancy : A period in an organism's life cycle when growth, development, and (in animals) physical activity are temporarily stopped is called dormancy.]

🔅Reproduction in Humans

🔹 Humans reproduce sexually i.e sexual 

      reproduction takes place in them.

🔹To carry out this process humans have 

     a set of organs known as human 

     reproductive system.

🔹Reproductive system in human beings

     become active and functional at a

     definite age that is called puberty.

🔹Puberty in Boys: 13-14 years and in Girls

     11-12 years.

 The Male Reproductive System 

 🔹Male reproductive system consists of

     following sets of organs:

         Testes

         Epididymis

         Vas deference

         Urethra

         Penis and 

         Accessory glands.

 Testes : 

🔹Singular- testicle 

   Shape: Oval

   No. : 02(in a pair)

  It is also known as male gonads and

  primary sexual organ.

 🔹The transverse section of testis shows

  that each testis has several highly coiled

  tubules called seminiferous tubules.

🔹Seminiferous tubules helps/involved in

    the formation of spermatozoa(sperm).

🔹 It lies outside the abdominal cavity in a

    pouch like a structure known as scrotum.

🔹 Scrotum filled with a liquid known as

    Hydrocele( name of a disease).

🔹Temperature in scrotum is 3 degree

  Celsius lower than the temperature inside

  the body.

Diagram:👇

 🔹It secrets male sex hormone

    i.e Testosterone ( it helps in the

    formation of male gametes and maintains male sexual characteristics.)

 Epididymis :

🔹It is a long tube about 6 m long a highly

  coiled structure that remains attached to

  the testis and lie within the scrotal sac. 

🔹It stores spermatozoa or sperms and

  serves as a passage for their transport

  from the testis.

 Vas deferens  :

🔹It is also known as sperm duct. 

🔹It is the lower end of epididymis and

  joins the duct of seminal vesicle to form

  the ejaculatory duct which opens into the

  urethra.

Urethra :

  It i

Penis : 

Accessory Glands