Book excerpt: Spatial distribution -- Coevolution and diversity -- Food and feeding modes -- Gonochorism and males -- Hermaphroditism and selfing -- Parthenogenesis and unisexualism -- Clonals and stem cells -- Mitosis and meiosis -- Oogenesis and vitellogenesis -- Spermatogenesis and spermatophores -- Female- vs male-heterogamety -- Eutelism and parasitism -- Monogamy vs. Polygamy -- Semelparity vs iteroparity -- Spawning and oviposition -- Fertilization success -- Fecundity -- Direct and indirect life cycle -- Brooding and viviparity -- Feeding and non-feeding larvae -- Parasites and hosts -- Sex determination and differentiation -- Metamorphosis and recruitment -- Message from fossils -- Conservation -- Climate change.