Answer:
This can be explained with an example.
Let’s lake an example of two species 1 and 2.
Species 1 has a wide genetic diversity due to which organism are also diverse in phenotype. Their phenotype are:
Black, dark brown, brown, dark red, red, light red, pink, skin color.
From left to right organism are becoming less adapted to high temperature relatively.
For species 2: This species has less genetic diversity and its phenotypic diversity is as follow:
Black, red, Skin color.
From left to right organism are becoming less adapted to high temperature relatively.
Now if there is the sudden high temperature in the environment; 4 Types of phenotype will survive are black, dark brown, brown, dark red.
While there will only two types of organism in specie 2 which will survive are black, red.
So that’s how the diversity of organisms increase the chances that some will survive a major change in environment.