Do Organisms Create Exact Copies of Themselves
- Organisms reproduce and create new individuals of their kind. This is essential for the perpetuation of species.
- Information for the inheritance of features from parents to the next generation is present within chromosomes, in the form of DNA.
DNA and Chromosome
Modes of Reproduction used by Single Organisms
Fragmentation in Spirogyra
- However, multicellular organisms with cell differentiation, when cut into small pieces, may regrow into a complete organism with the help of specific cells. This process is known as regeneration.
Example: Hydra and Planaria.
Regeneration in Planaria
- Yeast and Hydra may grow a bud from their body, which can detach and mature into a complete organism. This is known as budding.
Budding in Hydra
- Many plants can give rise to new plants through their vegetative parts like roots, stem and leaves. This is known as vegetative propagation.
Example of Vegetative Propagation
In many fungi, like Rhizopus, spore formation takes place in spore sacs called sporangia. Being thick-walled, these spores survive harsh conditions and can grow into a complete organism under favourable conditions.
Spore Formation in Rhizopus
Why the Sexual Mode of Reproduction?
Sexual mode of reproduction involves combining DNA from two different individuals, thereby resulting in faster variations.
During sexual reproduction, two germ cells fuse to form a zygote, giving rise to a new individual. Germ cells are produced as a result of special cell division called meiosis, which results in halving of chromosomes number. The chromosome number is restored after fusion.
Sexual Reproduction in Flowering Plants
Reproduction in Plants