A bird enters the mouth of crocodile and feed on parasitic leeches. The bird gets food and crocodile gets ribs of blood sucking leeches. Both the partners can live independently. Such an association is

Which of the following is capable of causing green house effect in the environment

$A$ : Different ecotypes of a species despite being genotypically different are interfertile.
$R$ : They are locally natural selections from a pool of genetic variations found in gene pool of a species.

“Pedology” is the study of

પરભક્ષણ, પરોપજીવન અને સહભોજીતા એ સામાન્ય લક્ષણોનું વિભાજન કરે છે, એટલે કે $.......$

The instrument which measures wind velocity is