Describe the structure of a nucleosome.

OR

Mention the evolutionary significance of the following organisms :

(a) Shrews

(b) Lobefins

(c) Homo habilis

(d) Homo erectus

The Nucleosome core particle contains two copies of each Histone protein (H2A, H2B, H3 and H4) and 200 basepairs(bp) of DNA helix wrapped around histone octomer.

OR

The evolutionary significance of the given organisms are as follows:

(a) Shrews:

_• Shrews were the first mammals.These were long tailed, insectivorous, squirrel-like organisms.

_• They gave rise to primitive primates.

_• Eg: leones ,trasiers at the beginning of the Palaeocene era.

(b) Lobefins:

_• Lobefins evolved into the first Amphibians that lived in both water and land.

_• Modern day frogs and salamanders have evolved from lobefins.

(c) Homo Habilis:

_• The first Human-like primates, lived in Africa about 2 million years ago.

_• They had brain capacity of 700cc.

_• They are also called as Handy Man , as they were first and most skilful tool makers.

(d) Homo erectus:

_• These were the next primates evolved from Homo Habilis about 1.57million years ago.

_• They had large brain with the capacity of 800-1100cc and were Omnivores.

_• They had an erect posture.

_• They used to hide to protect their body and buried their dead.