$A$ population is

$A$ : Population ecology is a link of ecology to population genetics and evolution.
$R$ : Natural selection operates at population level to evolve the desired traits.

Community is

$I.$ Group of independent, interacting populations of same species

$II.$ Group of independent and interacting populations of same species in specific area

$III.$ Group of independent interacting populations of different species in a specific area

$IV.$ Group of independent and interacting populations of different species in different area

Select the correct option

The study of inter-relationship between living organisms and their environment is called

Ecology is basically concerned with how many basic levels of organisation?