Mollusca is the second largest phylum after Arthropoda.
The members of this group are known as mulluscs or mullusks.
The phylum is estimated to have more than eighty-five thousand species().
Most of the species live in water, and it is estimated that twenty-three percent of all marine species are mulluscs.
It is segregated into seven classes, namely, Scaphopoda, Monoplacophora, Cephalopoda, Gastropoda, Bivalvia, Polyplacophora, and Aplacophora.
Examples of species in the phylum and their ecology
Class Aplacophor has worm-like organisms that are mostly found in the benthic marine environment.
Class Monoplacophora organisms have a cap-like shell that encloses their body. The shape of the shell varies from circular to ovate(). They include Neopilina galathaea
Class Bivalvia members live in fresh and marine waters. They bury themselves in sea beds, attach themselves to hard places or lie on the seafloor. They include scallops and oysters.
Class Gastropoda includes organisms such as snails and slugs. They are commonly found in gardens and marine conches.
Effects of human activities on mulluscs
Human activities have impacted on the numbers and reproduction of organisms in the phylum.
Pollution, especially on water pollution, is killing the organisms, and some face extinction.
People are fetching shells to use them to make ornaments and to decorate surfaces such as walls.
Besides, overfishing has led to the organisms being caught together with fish and end up in an ecosystem they cannot survive in.
Conservation status
Class Aplacophor organisms still exist in large numbers
Class Monoplacophora was believed to be extinct until in 1952 when scientists discovered Neopilina galathaea. Since then, they have found more than ten species of the class()
Class Bivalvia are believed to be few and are likely to face extinction
Class Gastropoda still exist in large numbers, although the number has been reducing due to human activities such as the occupation of their habitats and farming