Reproduction in Organisms-Events in Sexual Reproduction

Events in Sexual Reproduction

1. Pre-Fertilization events.
2. Fertilization.
3. Post -Fertilization events.

Pre-Fertilization events.

Gamatogenesis & Gamete transfer.
Gamatogenesis: It is the process of formation of 2 type of gametes.ie, male & Female gametes.
Male gamete is called sperm.
Female gamete is called Egg or Ovum.

Then Gametes transfer through sexual copulation or contact.

Homogametes/Isogametes And Heterogametes.

Homogametes

The male and female gametes are similar.Eg: Cladophora.

Heterogametes.

The male and female gametes are dissimilar.Eg: Egg and sperm in humans.and Fucus in algae.

Sexuality in organisms

Self Fertilization
The fusion of male and female gametes from the same hermaphrodate individual.

Some questions:

Prepare note on hermaphroditism in tapeworms and earthworms

.
Tapeworms-self fertilization.
The sperm produced in the testis of one individual can fertilise the egg produced by the same individual

.
In Earthworms-Cross fertilization.
The sperm of one individual fertilise the egg of another individual.

REPRODUCTION IN HUMANS

Puberty: The period during which adolescents reach sexual maturity and become capable of reproduction.


Secondary sexual characters in human beings...(Changes that indicates sexual maturity).

Secondary sexual characters in Male....
Enlargement if penis & glands of the reproductive tract.
Increased muscle development.
Enlargement of larynx,So deepning of voice.
Growth of public hairs,extra hair on face, And also at the arm pits & on the chest.

Secondary sexual characters in Female...
Growth of Breasts and external genetalia.
Broadning of pelvis.
Typical feminine contour due to increase in deposits of fats in thighs & face.
Growth of public and axillary hair.
Initiation of mensturation and ovulation.

Menstrual Cycle: The process of ovulation and menstruation in women and other female primates,like monkeys and apes.

Oestrous Cycle: A recurring period of sexual receptivity and fertility in many female non-primate mammals. Eg: Cow,dog,rat,cat,etc...

Seasonal breeders:animals living in natural wild conditions breed only at favorable seasons.

Continuous breeders: Animalsthat breed throughout their reproductive phase.Eg: Deer,Goat etc...

Senescence: It begins at the end of reproductive phase.Growth deteriorates with age.

Fertilisation:It is the process of fussion of sperm and egg to form the zygote.

Sperm + egg = Zygote

Embryogenisis: The formation of the embryo from the zygote and its development.

Sexual Reproduction

Sexual Reproduction

Sexual Reproduction involvs following processes.

*Formation of male & female gamates.
*Fusion of male & female gamete to form zygote.
*Development of zygote into the organism.
*The offspring produced by sexual reproduction is not exactly similar to morphology,But in internal   structure   follows similar pattern.

Common Features of sexual reproduction in organisms
A. Juvenile phase (In Animals)
   Period of growth & maturity of organisms prior to sexual reproduction.
B. Vegitative phase (In iv plants)
   Period of growth of a plant before it reaches sexual maturity.

Reproductive phase.

The period during which the organism producesyoung ones.
And plants are categorized into3 based on their lifespan.Annuals,Biennials&perennials.

Annuals: Grows and reproduces with in one year.Eg:Peperomia

Biennials: A plant that lives for 2 years, At first year it shows maximum vegitative growth & in next year it reproduces.Eg:Amorphophalus

Perennials: A plant which lives more than two years. Eg: all type of big trees...

Asexual Reproduction

Asexual And Sexual Reproduction

When offspring is produced by a single parent With or without involvement of gamate formation is called Asexual Reproduction
When two parents (opposite sex) participate in the reproductive process and also involve fusion of male and female gametes is called Sexual Reproduction
Difference in
Sexual                                        &                      Asexual reproduction

male & Female parents are evolved.                                   Only single parent involved
Morphologically & Genetically dissimilar                             Morphologically & Genetically similar to parents(Clones)
to parents                            
Formation of male & Female Gamate
Fussion of gametes


Asexual Reproduction.......
In Asexual reproduction,A single parent is capable of producing off spring.As a result,the offspring that are produced are not only identical to one another but are also exact copies of their parent.
Are these offspring likely to be genitically identical or different ?
Theoff springs will be genetically identical.This is because of Asexual reproduction,We know that in Asexual reproduction only one parent takes part in reproduction process.So, there no mixing of genes.
thereby the off spring will be morphologically and genitically similar to parent. Such morphologically and genitically similar individals are called CLONES


Asexual reproduction is common among single celled organisms, and in plants and animals with relatively simple organisations.In protists and Moneran, the organism or the parent cell divides into 2 give rise to new individuals.Thus, in these organisms "cell division" is itself a mode of reproduction.
Many single celled organisms reproduce by "binary fission".In yeast,the division is unequal and small "buds"produced later seperated and mature intonew yeast organisms (cells).Members of the Kingdom Fingi & simple plants such as algae have special reproductive structure called "Zoospores"Which is microscopic motile structures.
Other common Asexual reproductive structures are "conidia(penicillium),buds(Hydra) & gemmules(sponge).


While in animals & other simple organisms the term Asexual is used unambiguously,in plants, the tearm "vegetative propagules".Obviously,sine the formation of these structures does not involve 2 parents,the process involved is asexual.

Is vegitative reproduction also a type of asexual reproduction?Why do you say?Is the tearm clone applicable to the offspring formed by vegetative reproduction ?

Vegetative reproduction also a type of asexual reproduction.So there is no formation & fussion of gamates involved,in plants the offsprings are formed from Adventitious Buds,Adventitious roots,offset,buds etc...

Vegetative propagules & examples

Rhizome    :               Ginger
Bulb       :               Onion
Stem tuber :               Potato
Runner     :               Hydrocotyle,Oxalis
Sucker     :               Chrysanthemum,Banana
Offst      :               Pistia
Aerial stem:               Sugar cane,Pepper,Rose
Offset     :               water Hyacinth
bulbil     :               Avage
Root       :               Bread fruit tree,Curry leaf plant
Leaf Buds  :               Bryophyllum

Some plants reoroduces both sexually & asexually.
For eg: Pepper, Sugar cane, Curry leaf Plant.

Some Questions For You........

1.  The vegitative propagation in Chrysanthemum is means of ?
    Ans: Sucker.
2.  I which type of reproduction Unequal daughter cells are produced?
    Ans: Budding.
3.  Sugar cane is normally grown By ?
    Ans: Stem cutting.

             
    Do you think 'Dolly' the first cloned sheep is an exact copy of its mother? Why?

Ans:Yes Dolly is an exact copy of its mother.the offspring produced by cloning are Morphologically & Genetically similar to its parent.

    Do you agree that Budding is an asexual reproduction ?

Ans:Yes,Budding is an asexual reproductive meathod.Its commen in yeast cells.The Bud is formed from the parent cell.It grows & seperated from the parent cell to form a new yeast cell.
    And here only one parent takes paet in the process of reproduction & no fertilization takes place.So,its an asexual reproduction.

    What is Budding ?(reproduction)

Ans:Its atype of asexual reproduction commenly in Hydra, The part of the body wall bulges outwards & eventully form a new individual whic comes detached from the parent.
  
    Malarial parasites Divides into many daughter cells simultaneously through multiple fission.State an advantage the parasite gets because of this type of reproduction.
Ans:Due tp this type of reproduction a large number of offsprings are produced at the same time.

REPRODUCTION IN ORGANISMS

Each and every organism can live only for a certain period of time. The period from birth to natural death of an organism represents its life span. Life span of few organisms are............ (in Years)

Elephant                                              70-80 years
Dog                                                    13-15 years
Cat                                                     25 years
Lion                                                    35 years
Horse                                                 40 years
Butter Fly                                           1-2 weeks
Crow                                                 15 years
Parrot                                                140 years
Cow                                                   22 years
Crocodile                                           60 years
Fruit Fly                                             24 Hours
Tortoise                                              100-150 years
Rose                                                  15 years
Banana tree                                        15 years
Rice plant                                            3-7 months
Banyan tree                                        400 years or more than..................

                                                         It is interesting and intriguing to note that it may be as short as few days or as long as a few thousand years? Between these two extremes are the life spans of most other living organisms.The life spans of organisms are not necessarily correlated with their sizes; the sizes of crows and parrots are not very different yet their life spans show a wide differences.Similarly, a mango tree has a much shorter life span as compared to a peepal tree.Whatever be the life span, death of every individual organism is certainty. i.e., no individual is immortal, except single-celled organisms.

Now you may be think about "Why there is no natural death in single-celled organisms "?
Ans: There is no natural death takes place in single cell organism.Because in single cell organisms,they produce next generation by binarry fission.That means the mother cell divides into two daughter cells.
new single cell organism is formed.

Have you ever wondered how vast number of plant and animal species have existed on earth for several thousands of years? There must be  some processes in living otganisms that ensure this continuity. Yes i am talking aabout Reproduction, Something that we granted.

Reproduction is defined as a biological process in which as organism gives rise to Young ones(off springs)similar to it self.
In Simple words REPRODUCTION is the process of formation of off springs by Asexual or Sexual means.

There is a large diversity in the biological world and each organism has evolved its own mechanism to multipl and produce offspring.The organism's habitat, its internal physiology and several other factors are collectively responsible for how it reproduces.

Amoeba reproduces by Binary Fission (Asexual Reproduction).

It divides in half by a process called fission, producing two smaller daughter cells.This is an example for there is no natural death in single-celled organisms

Hydra reproduces both asexually and sexually. Asexual Reproduction takes by Budding method.
In Hyda small bud are develop in the body then the buds are transforms into new offsprings