Reproduction
Reproductive stratergiesReproduction is immensely important in the animal and plant kingdom, as it ensures the survival of all forms of life. There are two types of reproduction: sexual and asexual, asexual being the most common type. Sexual reproduction occurs when a female's egg and male's sperm fuse together during fertilisation to produce DNA replication, which results in the creation of a single-celled zygote (which includes genetic information from both parents). Asexual reproduction occurs when offspring arise from a single organism, and inherit the genes of that parent only. This is the primary form of reproduction in single-celled organisms, for example protists, archaebacteria, and many plants and fungi.
There are 3 types of mating systems: monogamy, polygamy and promiscuity. Monogamy involves species forming forming a 'pair bond' for one or more breeding systems, or for life. Polygamy involves either one male or one female having multiple partners during a breeding season. Finally, promiscuity involves males and females within a social group engaging in multiple and indiscriminate matings. In terms of the amount of offspring an organism creates, there are two ends of the spectrum, labeled: 'quick and many' (r-selection) and 'slower and fewer' (K-selection). There are many species that fall between these two strategies. The 'quick and many' strategy is seen in species that are sexually mature quickly, produce large amounts of offspring or breed frequently (or both), and perhaps put none or a limited amount of parental care into their offspring. The 'slower and few' strategy is seen in species that mature slowly, breed later, produce fewer and larger offspring and may put extensive parental care into their offspring. Corals have adapted their reproduction strategies to survive in their diverse and dynamic environments. In terms of sexual reproduction, corals reproduce through: broadcast spawning and brooding. Broadcast spawning occurs when the corals release their eggs and sperm collectively in an annual event in the year. The released gametes drift t the water surface where fertilisation takes place and after a couple of days, the embryos would have developed into planulae, also known as coral larvae. Brooding spawning occurs when fertilisation and embryogenesis is internal, and happens before the larvae are released. Brooding coral species demonstrate to have reproductive seasons from a few months to almost continuously throughout the year, and typically produce larvae which already contain zooxanthellae, compared to broadcast spawners' larvae which generally take up their zooxanthellae shortly after settlement. |