A recall on the postulates of Darwinism
Criticism against Darwinism:
Following are the major criticism against Darwinism:
- All of the variations in organisms may not be a result of adaptation to new demands.
- Environmental factors are not the only causes of variations. They may be caused even by other factors.
- The variations which are not useful may also be inherited. Example: Vestigial organs.
- Darwinism was unable to explain the various reasons for variation as well as the mode of variation transmission.
- There was no differentiation made between somatic and germ cell variants.
- Natural selection is an important component, but it is not the only one that contributes to evolution.
- Small variations in small groups cannot result in speciation.
- In biological evolution, speciation is a macrophenomenon.
- Darwinism was unable to account for the most important factors that can lead to speciation.
- No consideration was given to the genetic basis of inheritance.
From the above discussed critics we can concluded that why the principles of heredity and genetics that we covered before are so important for understanding evolution. Even Charles Darwin, who proposed the theory of species evolution by natural selection in the nineteenth century, couldn't figure out how it worked. Ironically, he could have done so if he had recognised the relevance of the research being conducted by his Austrian contemporary, Gregor Mendel. But Mendel, too, failed to see Darwin's findings as pertinent to his own!
Differences between Lamarckism and Darwinism:
|1.||According to this theory, there is a internal vital force in all organisms.||This theory does not believe in the presence of a internal vital force.|
|2.||This theory considers that new needs or desires produce new structures leading to the change in the habits of the organisms.||New structures leading to the change in the habits of the organisms is not a part of Darwin's selection theory.|
According to this theory, if an organism constant uses a particular organ, the organ would be better developed and its disuse results in its inactiveness.
|An organ develops or generates only due to continuous variations.|
|4.||Struggle for existence is not considered here.||Struggle for existence plays a prominent role in this theory.|
|5.||According to this theory, all the acquired characteristics are inherited by the next generation.||According to this theory, only useful variations are transferred to the next generation.|
|6.||This theory does not believe in survival of the fittest.|
Darwin's theory of natural selection the based on the survival of fittest.
It is the process by which humans select the traits useful to them for improving the qualities of plants and animals.
Animal Husbandry has resulted in the emergence of new species.
For example, the reproductive isolation in fruit flies results in species differences after eight generations by feeding on various foods.
Hybridisation between two species can result in a unique phenotype, as seen in Elephantidae. Individuals with the required characteristics are chosen and allowed to breed with one another. When this artificial selection process is repeated over a long period of time, a new breed is created. This approach is used to grow a variety of beneficial plants, such as wheat, rice, legumes, and vegetables.
Differences between natural selection and artificial selection:
|S.No||Natural selection||Artificial selection|
|1.||It involves a natural selection process that favours the fittest individuals capable of dealing with a variety of conditions.||It is a process in which the organisms with desired characters are chosen by man.|
|2.||It has a high chance of survival.||It does not always increase the chances of survival.|
|3.||It is a slow and long process.||It is a fast process.|
|4.||It is controlled by nature.||It is controlled by humans.|
|5.||It is carried out on all types of organisms.||It is carried out on selective organisms of humans desires.|
|6.||It is entirely based on having an adaptable personality and being able to cope in a variety of natural situations.||Selection is made on the basis of required character.|
|7.||It transforms the entire population of a species.||A new variety of species is formed.|
|8.||Example: Darwin's finches||Example: It's frequently done on pets or animals maintained for economic reasons.|