Reproduction in organism

 Reproduction in organism

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Some IMP points

•  The period from birth to the natural death of an organism represents its life span.

•  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 difference.
•  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 a certainty, i.e., no individual is immortal, except single-celled organisms. 
•  

Approximate life spans of some organisms

1. Elephant (65-90 years)
2. Rose (5-7 years)
3. Dog (20-30 years)
4. Butter fly (1-2 weeks)
5. Crow (15 years)
6. Banana tree (20-25 years)
7. Cow (15-25 years)
8. Parrot (140 years)
9. Rice plant (3-4 months) 
10. Tortoise (100-150 years) 
11. Banyan tree (200-300 years)
    
12. Crocodile (60 years) 
13. Horse (62 years) 
14.  Fruit fly (about 20-30 days) 

• Reproduction is defined as a biological process in which an organism gives rise to young ones (offspring) similar
  to itself.
  
• The offspring grow, mature and in turn produce new offspring. Thus, there is a cycle of birth, growth and death.
• Reproduction enables the continuity of the species, generation after generation.
• The organism’s habitat, its internal physiology and several other factors are collectively responsible for how it reproduces.
• When offspring is produced by a single parent with or without the involvement of gamete formation, the
• reproduction is asexual. When two parents (opposite sex) participate in the reproductive process and also involve
• fusion of male and female gametes, it is called sexual reproduction. 

 

ASEXUAL REPRODUCTION

• In this method, a single individual (parent) is capable of producing offspring. 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 genetically identical or different? Answer will be genetically identical.
•  The term clone is used to morphologically and genetically similar individuals
•  Many single-celled organisms (monerans and protists) reproduce by binary fission.
•  Member of kingdom fungi and algae reproduce through special asexual reproductive structures called zoospores.
•  Conidia (Penicillum) buds (Hydra) and gemmules (sponge) are other common asexual reprodutive structures 
• In plants, the units of vegetative propagation such as runner, rhizome, sucker, tuber, offset, bulb are all
  capable of giving rise to new offspring. These structures are called vegetative propagules.

 

SEXUAL REPRODUCTION

•  Sexual reproduction involves formation of the male and female gametes, either by the same individual or by
• different individuals of the opposite sex. These gametes fuse to form the zygote which develops to form the
• new organism. It is an elaborate, complex and slow process as compared to asexual reproduction.
•  Because of the fusion of male and female gametes, sexual reproduction results in offspring that are not identical
• to the parents or amongst themselves.

•  A study of diverse organisms–plants, animals or fungi–show that though they differ so greatly in external
• morphology, internal structure and physiology, when it comes to sexual mode of reproduction, surprisingly, they
• share a similar pattern. Let us first discuss what features are common to these diverse organisms.
•  All organisms have to reach a certain stage of growth and maturity in their life, before they can reproduce sexually.
• That period of growth is called the Juvenile phase. It is known as vegetative phase in plants. This phase
• is of variable durations in different organisms.
•  In some plants, where flowering occurs more than once, what would you call the inter-flowering period – juvenile
• or mature? Answer will be mature