Question

a) DNA changes accumulated over a time span has resulted in evolution of complex organs. Discuss with the help of an example of origin of eye.

(b) Do all variations in a particular species have equal chances of survival in an environment ?

Answer 1

DNA changes accumulated over a time span has resulted in the evolution of complex organs. For eg. eye is a complex body part may have originated to detect light  for such the rudimentary eye in planaria. Insects, octopus and vertebrates too have them but with different origins. now eye is very common feature and definitely have accumulated through generations.

b) no, all the variations do not have equal chances of survival in an environment. take the example of bacteria living in ocean. if suddenly the temperature of the ocean rises, the variants resistant to heat would probably survive but other variants would be wiped out.

hope this helps!!

Answer 2

A)
Yes DNA changes accumulated over a time span has resulted in the evolution of complex organs through natural selection. Eyes have time span of around 500 million years and have evolved from Planaria and Hagfish in small patches like structures resembling to eyes to complex structures in vertebrates including human.
B)
No, all variations in species do not have equal chances of survival against any change in environment. For example all birds living in a hot climate can't bear cold climate and only a few having surviving ability from cold will left behind while all others will die.