Question

In a habitat, there are red bugs and green bugs. The birds prefer the taste of the red bugs, so soon there are many green bugs and few red bugs. The green bugs reproduce and make more green bugs and eventually there are no more red bugs. The given example can be related to
(a) Adaptive radiation
(b) Natural selection
(c) Genetic variation
(d) All of the above

Answer 1

Here the organisms which survive the struggle for existence transmit their heritable variations to the next generation. In this process, nature selects and preserves the favorable variations and rejects unfavorable or harmful ones. It means only those individuals will survive, who adapt themselves to the change in the environment.

Complete answer:
According to the theory of natural selection, nature supports the survival of the fittest. In the given case, bugs adapted the green colouration to survive. They were selected by nature as the fittest. Natural selection is a complex mechanism in which the total environment determines which members of a species would survive to reproduce and pass on their genes to the next generation. Operation of natural selection over many successive generations results in preservation and progressive accumulation of successful heritable variations in natural populations. It may also cause a progressive increase in the frequency of profitable variations.

Additional Information:
- In the whole struggle for existence, natural selection and the genetic transmission and accumulation of favourable variations over many successive generations tend to progressively increase the adaptivity, fitness, survival value and evolutionary potentiality of organisms.
- Darwinian theory of natural selection holds three cardinal aspects;

1. Nature preserve small useful and heritable variations,
2. Accumulation of useful variations over many generations leads to the origin of new species from existing ones.,
3. All complex organisms of the present and the past are the products of evolution from simple ancestors.
   - This leads to the gradual transformation of a species to a new one. This is called origin of species by natural selection.
   So, the correct answer is '(b) Natural selection'.

Note:
- Survival of the fittest is the natural phenomena in which organisms having favourable adaptive variations or adaptation survive the struggle for existence.
- Those with neutral and harmful variations eventually perish. Thus the fittest individuals are best adapted to the environment.
- Darwinian explained the survival of the fittest by citing the example of giraffes.