In this chapter you will learn
- Definition of reproduction its main types. And differences between asexual and sexual reproduction
- Different types of asexual reproduction in plants &animals
- Advantages and disadvantages of vegetative propagation
- Sexual reproduction in plants and animals
- Definition pollination, its types and significance
- Life cycle of a flowering plant and process of double fertilization
- The formation and dispersal of seeds and fruits, structure of seed and its germination
- fertilization and stages of development in frog
One of the basic characteristics of living things is their ability to reproduce. Reproduction is a biological process by which living things produce their young ones which are similar to the parents. Reproduction ensures the continuity of a species and also helps the organism to adapt itself to the changing environment.
16.1 types of reproduction
There are two principal types of reproduction, asexual and sexual. The organisms produced through asexual reproduction are genetically identical among themselves and also to their parents. These organisms fail to cope with the changing environment and if continue to reproduce this way, ultimately become extinct/ asexual reproduction is advantageous for the organisms as this method is efficient, a shorter time is taken for the species to inhabit or colonize the habitats. In the long term the organisms must reproduce by sexual reproduction to become successful over longer periods of time.
“A population of genetically identical individuals produced from a single parent is called a clone”
In asexual reproduction no gametes are involved, all the offspring’s are produced from single parent by mitotic cell division.
The most important difference between asexual and sexual reproduction is that in the former, there is no mixing of hereditary material prior to the formation of new organism, but in the latter there is always mixing of hereditary material, either between two cells of the same organism or between two cells of different organisms of the same species.
The none mixing of hereditary material in asexual reproduction does not improve the genetic make up and does not produce variety among the descendents. So if environmental conditions, to which these organisms are well adapted, are changed, this would affect all the members of that species. Suppose if asexually produced plant has no resistance to a particular disease the whole population could be wiped off. In contrast the genetic variability is produced by sexual reproduction, which results in most cases by meiosis and mixing of hereditary material. This genetic variability helps the organisms to live successfully in changing environment. So some of the offspring would survive, even if most of them are wiped off by a particular disease, because the surviving organisms have the resistance to that disease. Some of the common methods of reproduction in plants and animals are binary fission, multiple fission, budding, spore formation, vegetative propagation, regeneration, parthenogenesis and sexual reproduction.