reproduction in organisms class 12 CBSE NCERT to the point

 reproduction in organisms classes 11 CBSE NCERT 

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1. lifespan is the period from birth to the natural death of an organism that represents its lifespan.

can u tell me the difference between life expectancy and lifespan???? included in neet for mbbs, if no, comment on me and learn the notes given in the competition column.

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•      death of every individual is a certainty, no individual is immortal, except single-celled organisms.
• reproduction is defined as the biological process in which an organism gives rise to a young one's offsprings similar to itself. the offspring grow, mature, and in turn, produce new offerings .thus, there is a cycle of birth, growth, and death.
• reproduction enables from generation after generation. 
• it has two types based on the number of individuals:- asexual and sexual reproductions.
• asexual reproduction:- this is the type of reproduction in which only one parent is involved without the involvement of gamete formation.
• sexual reproduction:- this is the type of reproduction in which two opposite sexes are involved that involves the fusion of two gametes .called sexual reproduction.
• asexual reproduction:- 

1. the offspring formed by asexual reproduction means single parents are exact copies of the individuals of their parent.
2. the clone is used to describe such morphologically and genetically similar individuals.
3. in protista and monerans, the organisms and the parent cell divides by mitosis into two to give rise to new individuals. 
4. theses organisms divide by cell division, the type of reproduction is divided by binary fission and multiple fission .yeast undergoes binary fission as it develops buds and remains attached to it until it gets matured. amoeba also divides through this kind of binary fission only in favorable conditions, but in an unfavorable condition, it divides by multiple fission as it withdraws pseudopodia in develops three-layered covering outside itself the process by which it develops called encystation. then, in favorable condition, the cyst burst outs and spread into the surroundings and release spores that mature into new amoebae gradually the process by which this occurs is called sporulation.
5. another member like kingdom fundi and simple plants like algae reproduce through special asexual structures called spores, commonly called zoospores, that are motile in structures. other asexual reproductive structures are conidia (Penicillium), buds in hydra, gemmules in the sponge, etc.
6. _______________________________________
7. terror of Bengal: called water hyacinth grows in standing water through their invasive weeds. it drains out all the oxygen from water and leads to the death of aquatic life.
8. nodes: These are some meristematic cells that tend to grow present on the modified stems of the leaves and notches. When they come in contact with other soil and water, they propagate into a new flower and frows to ones mature once .like the adventitious buds in plant bryophylum.
9. asexual reproduction or vegetative reproduction, as well as sexual reproduction, are exhibited by the higher plants.

• sexual reproduction 

1. it involves the formation of female and male gamete either by the same individual or different individuals of the opposite sex.
2. it is an elaborate, complex, and slow process compared to asexual reproduction, because of the fusion of male and female gamete, it results in variation.
3. all organisms have to reach a certain age of growth and maturity in their life. before they reach to reproductive stage. this growth phase is called the juvenile phase in animals and the vegetative phase in plants. this phase is different in duration in different types of organisms.
4. the end of this growth phase is called senescence.
5. the annual and biennial types show clear-cut vegetative, reproductive, and senescent phases, but in perennial species, it is very difficult to clearly define these phases.
6. a bamboo species flower only once in50-100 years, produce a large number of fruits and die.
7. another plant, strobilus kunthiana called neelranji, flowers in one =ce in 12 years. 
8. in case, laying eggs is not related to reproduction but is commercial exploitation for human welfare. 
9. as we have in human females called menstrual cycles and in non-primates, we see the estrous cycle. 
10. events in sexual reproduction - pre- fertilization, fertilization, post-fertilization, etc.
11. PRE-FERTILISATION EVENTS:- 1.gametogenesis  2.gamete transfer gametogenesis is the process of formation of the two types of gametes - male and female.

• gametes are haploid cells.
• in some algae, the two gametes are so similar in appearance called homogenates (isogametes) and different ones called heterogametic.
• organism are games , female gametes in animals called ovum dn in plants egg, and whereas in males are called sperm in humans and antherozoids in plants, etc.
• sexuality:- sexual reproduction in organisms generally involves the fusion of gametes from two different organisms.
• plants may both male and female reproductive structures in the same plant called bisexual plants, or different plants called unisexually.
• in several fungi and plants, such as homothallic organisms and monoecious and are used to denote