Answer:
Step-by-step explanation:
I. Darwin’s theory of evolution
Organic evolution by Charles Darwin is emphasized as “Descent with modification” stating that the present complexities in animals and plants are as a result of evolution from simpler forms that existed earlier through eventual changes.
II. Lamarckian Theory Of Evolution
The first theory of evolution was Lamarckism proposed by Jean Baptiste de Lamarck, the outline of this theory came into the picture in 1801 only. He is responsible for coining terms “Annelida” and “invertebrates”.
Lamarck’s Propositions
4 main factors are:
Internal vital force – this force causes all living things and their component parts to be continually increased
Effect of environment and new needs – environmental changes have an impact on living entities causing them to change leading to new needs. These needs generate new structure altering habits of entities
Use and disuse of entities – more usage of organs causes it to develop better, disuse of organs leads to degeneration
Inheritance of acquired traits – characteristics adapted as a result of all these above factors passing on to the next generations. It is a continuous process. These variations are accumulated over generations leading to the formation of a new species.
Mechanism Of Organic Evolution
The phenomenon of genetic variation is basic for organic evolution. It is upon this that selective forces act for evolution to take place. The mechanism of evolution emphasizes on:
Descent and genetic differences which can be inherited to the next generation. Genetic drift, migration, mutation, natural selection as mechanisms of change
Significance of genetic variation
Consequences of a reduction in genetic variation and random nature of genetic drift
Impact of various species on each other’s evolution process via co-evolution
Role of differential reproduction, variation, heredity in evolution by natural selection
Evolution is observed in a population as it contains genes in the gene pool, changes in this pool cause evolution.