Question

Define:

(a)Juvenile phase

(b)Reproductive phase

(c)Senescent phase.

with details Explaination

Answer 1

(a)Juvenile phase : All organisms have to reach a certain stage of growth and maturity in their life before they can reproduce sexually. That period of growth is called juvenile phase. However, this phase is known as vegetative phase in plants. This phase is of different durations in different organisms.

(b)Reproductive phase: The end of juvenile/ vegetative phase marks the beginning of reproductive phase. During this phase, the organisms produce offspring. In higher plants, this phase can be easily seen when they come to flower but in animals, the juvenile phase is followed by morphological and physiological changes prior to active reproductive behaviour. The reproductive phase is also of variable period in different organisms like some plants, flower throughout the year while others show seasonal flowering. In animals like birds lay eggs seasonally “but when in captivity (as in poultry farms) can be made to lay eggs throughout the year. Placental female mammals, undergo cyclical changes in reproductive organs during this phase.

(c) Senescent phase: It begins from the end of the reproductive phase. During this phase of life span, there is progressive deterioration in the body (like slowing of metabolism, etc.). Old age ultimately leads to death.

(a)Juvenile phase : All organisms have to reach a certain stage of growth and maturity in their life before they can reproduce sexually. That period of growth is called juvenile phase. However, this phase is known as vegetative phase in plants. This phase is of different durations in different organisms.

(b)Reproductive phase: The end of juvenile/ vegetative phase marks the beginning of reproductive phase. During this phase, the organisms produce offspring. In higher plants, this phase can be easily seen when they come to flower but in animals, the juvenile phase is followed by morphological and physiological changes prior to active reproductive behaviour. The reproductive phase is also of variable period in different organisms like some plants, flower throughout the year while others show seasonal flowering. In animals like birds lay eggs seasonally “but when in captivity (as in poultry farms) can be made to lay eggs throughout the year. Placental female mammals, undergo cyclical changes in reproductive organs during this phase.

(c) Senescent phase: It begins from the end of the reproductive phase. During this phase of life span, there is progressive deterioration in the body (like slowing of metabolism, etc.). Old age ultimately leads to death.