Final answer:
Gonochorism is the condition where molluscs are distinctly male or female as opposed to being hermaphroditic. This strategy is opposite to hermaphroditism, which is where one organism has both male and female reproductive parts. Most mollusks are gonochoric and reproduce through separate sexes with various stages of larval development.
"The correct option is approximately option B"
Step-by-step explanation:
The condition in which molluscs are either male or female, rather than hermaphroditic, is known as gonochorism. While certain molluscs like snails possess hermaphroditism, the majority of molluscs are dioecious, meaning individuals are distinctly male or female, and this sexual differentiation strategy is what defines gonochorism. Unlike hermaphroditism, where individual organisms have both male and female reproductive organs, gonochoric species rely on the presence of two separate sexes for reproduction. Mammalian sex determination, for instance, typically utilizes an XY chromosome system, in which XX denotes a female and XY denotes a male—a system shared by some insects and plants as well.
Gonochorism is in contrast to strategies like hermaphroditism, wherein organisms, such as earthworms, slugs, and snails, may possess both male and female reproductive organs, potentially allowing for self-fertilization or reciprocal mating with another of their species. Mollusks exhibit a variety of reproductive mechanisms, and fertilization can be either internal or external based on the species. Aquatic mollusks, which mostly adhere to gonochorism, release their gametes into the water column where external fertilization occurs. The resulting zygote typically develops into a trochophore larva, which may then pass through additional stages like the veliger before maturing into the adult form.
Notably, species such as cephalopods bypass the larval stages, instead developing directly into miniature versions of their adult form. This adaptability in reproductive strategies underlines the diversity and complexity of life cycles within the molluscan phylum. The reproductive method and life cycle of each species are well-matched with their respective habitats and ways of life, reflecting an evolutionary adaptation that has enabled mollusks to inhabit a wide range of environmental niches.