Answer: (B) Pre-zygotic; post-zygotic.
Explanation:
Prezygotic isolation occurs before fertilization of eggs. It occurs between the two sex gametes and deter sexual reproduction between different species.
However, individuals are considered to be diverge on the phylogeny tree and different species, when they cannot reproduce.
Mechanisms of prezygotic isolation include habitat isolation, gamete isolation, mechanical isolation, behavioral isolation, and mating seasons.
Whereas, postzygotic isolation prevents the formation of fertile offspring. This phenomenon leads to production of an hybrid offspring from different species and this is a form of speciation in nature.
Mechanisms of postzygotic isolation include hybrid inviability, hybrid breakdown, and hybrid sterility.
Answer:
Charles Darwin spent almost 5 years in the voyage name HMS Beagle. This voyage made him famous as after returning, he formulated the "Theory of natural selection" as he was amazed by the geographical distribution of the wildlife and also collected fossils that helped him to formulate his theory.
Explanation:
Charles Darwin was the main contributor to the theory of evolution. Besides, he was a geologist, naturalist, and biologist. He first demonstrated the branching pattern of evolution on the basis of natural selection. 18 February 1809 was his birth date and he died in 1882. He explained the theory of natural selection with the help of finches residing in the Galapagos island. The change in the beak structure of the finches according to the availability of food illustrates the process of natural selection and hence the process of evolution.
