The world's most problematic aquatic weed is

Identify the correct statements from the following:
$(1)$ Succession occurring in dry areas is called xerarch succession.
$(2)$ The stage where plants can survive in open conditions throughout the year is the herb stage.
$(3)$ Ecological succession leads to a decrease in the net primary productivity of the community.
$(4)$ Primary succession takes an average of $1000$ years to complete.

$A$: Neither the community modifies the environment nor the environment forces the community to leave the place in the climax stage of succession.
$R$: Climax community is xerophytic in most of the types of succession.

How many of the following organisms are decomposers in a pond ecosystem?
Some algae,fungi,bacteria,floating plants,submerged plants,flagellates.

Maximum photosynthesis occurs through .......

If all the green plants were to disappear from the earth,what would happen?