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Q. Define the following terms:
(1) Juvenile phase
(2) Reproductive phase
(3) Senescent phase
Answer:
Juvenille Phase – It’s the time when an individual organism grows after birth but before reaching reproductive maturity. A juvenile is a living being that has not yet attained adulthood, sexual maturity or physical size. Juveniles can have a substantially different appearance than adults, especially in terms of colour, and they may not fit the same niche as adults. In many creatures, the juvenile is referred to as something other than the adult (see List of animal names).
Many insects, for example, reach sexual maturity in a short transformation called eclosion. For some, the transition from juvenile to fully adult takes longer — for example, puberty in humans. Juveniles undergoing this metamorphosis are frequently referred to as subadults.
When invertebrates achieve adulthood, they are totally developed, and their development and growth come to a halt. Their larvae or nymphs are their juveniles.
Reproductive Phase – This phase occurs when an individual organism reaches reproductive maturity and becomes sexually active, as the name implies. They reproduce and create progeny. Grasses can reproduce sexually through seed (sexual reproduction) or asexually through vegetative propogation (asexual reproduction) (tillers which arise from adventitious buds on culm nodes, rhizomes, and stolons). Only sexual reproduction involving flowers, pollination and seeds is covered in this section.
A grass plant must develop flowers with male and female components to generate seed, with certain exceptions (see apomixis). When the grass plant enters the transition stage where the shoot is “”inspired to blossom,”” the first steps leading to sexual reproduction take place. Floral induction causes the vegetative shoot apex (growing point) to gradually transform into a floral bud. Within a few minutes,
Senescent Phase – The slow decline of functional qualities of living organisms is referred to as senescence (/snsns/). The term senescence can apply to either cellular senescence or organism-wide senescence. At least in the latter half of an organism’s life cycle, senescence is defined as an increase in death rates and/or a decrease in fertility with increasing age.
With germ-soma separation, practically all multicellular creatures face senescence, but it can be postponed. The discovery in 1934 that calorie restriction can lengthen longevity by 50% in rats, as well as the existence of species with no senescence and theoretically immortal animals like Hydra, have sparked interest in postponing senescence and thus age-related disorders. Rare human mutations can produce diseases that hasten the ageing process.
