Question

Green lizards were observed in the region in the image. Changes in the geography of the region caused the formation of a stream, which divided the region into two halves. The left half developed a dark green environment, and the right half a comparatively lighter green environment. As a result, two geographically isolated populations, dark and light green lizards inhabited either side of the stream.
The region on the right has more light green lizards as a result of _______ . The new species will develop by way of __________ .

1.
A. Natural Seletion
B. Postzygotic isolation
C. Harmful Mutation

2.
A. Sympatric Speciation
B. Allopatric Speciation
C. Convergent Evolution

Answer 1

1. Natural selection. 
This environmental change, by resulting in two different types of lizards that match the colour of the environment in which they are in, indicates that there was a natural selection, probably from the lizards' predator, that could now see them better if they were in the vegetation not corresponding to their colour leading to the remaining of dark lizards in a dark vegetation, and light lizards in a lighter vegetation.

2. Allopatric speciation
This type of speciation is also known as geographic speciation. It is so because it occurs when populations of the same species are isolated from each other in such a way that there are no genetic interchanges and are pushed to evolve into different species. In this case, the lizards were isolated by the stream that divided the two new areas.

Answer 2

The correct options are as follows"
1.B.
Postzygotic isolation is a type of reproductive isolation which keeps species from mating with each other as a result of the differences that developed between them when they are separated by physical boundary. In the question given above, the lizard specie has been separated by the formation of a stream which divide the region into two.
2.B.
Allopatric speciation refers to the mode of speciation that occur when biological population of the same specie become isolated from each other to an extent that it interferes with genetic interchange. It usually occur as a result of change in the environment.