Clownfish breed only in sea anemones, sharing a symbiotic bond. “It is a strong, obligate symbiosis,” “Clownfish shelter in the anemone and are the only fish that do not get stung by the nematocysts of the anemone. The anemone benefits because clownfish can defend the anemone from fish that might eat it. They never live anywhere but, in the anemone”.
And now the anemones, like coral reefs in general, are under direct threat from the impacts of climate change. It works like this: The anemones share another symbiotic bond, with algae. Under stress in warming waters, the algae leave the anemones. If the algae stay away too long, the anemone starve to death, which leaves the clownfish without a home.

Standing crop is defined as the total amount or number of living things or of one kind of living thing (such as an uncut farm crop, the fish in a pond, or organisms in an ecosystem) in a particular area at any given time.

1 and 3 are correct.
India hosted the 13th Conference of the Parties to the Convention on Migratory Species (CMS COP13), a major United Nations wildlife conference, in Gandhinagar. The theme of the conference is “Migratory species connect the planet and together we welcome them home”.
The CMS is an environmental treaty of the UN that provides a global platform for the conservation and sustainable use of migratory animals and their habitats. It is the only global convention specialising in the conservation of migratory species, their habitats and migration routes. The pact was signed in 1979 in Germany and is known as the Bonn Convention. “CMS brings together the States through which migratory animals pass, the Range States, and lays the legal foundation for internationally coordinated conservation measures throughout a migratory range,”

Biomagnification, also known as bioamplification or biological magnification, is the increasing concentration of a substance, such as a toxic chemical, in the tissues of tolerant organisms at successively higher levels in a food chain.

Lichens are typically the first organisms to colonize bare rock. They are therefore the pioneer species in primary succession. Many organisms require soil before they can colonize an area. Lichens that colonize bare rock secrete acids that break down the rock and start the soil-production process. Also, as lichens die, they provide some organic matter that also contributes to soil. Mosses can then colonize the thin soil; as mosses die, the soil thickens more allowing other hardy species to colonize. The process continues until a mature forest forms, sometimes centuries later.