Define the following phases of the life cycle of an organism:
$(a)$ Senescent phase
$(b)$ Reproductive phase
$(c)$ Juvenile phase

(N/A) Senescent phase: This is the final stage of the life cycle,occurring after the reproductive phase. During this phase,hormonal changes lead to a gradual decline in the production of gametes,eventually leading to death.
$(b)$ Reproductive phase: This phase begins when the reproductive system becomes mature enough to produce functional gametes. The organism is then capable of mating and reproduction. This phase is characterized by significant hormonal changes. In humans,it typically starts at $12$ to $13$ years of age and lasts until $55$ to $60$ years.
$(c)$ Juvenile phase: This is the period of growth and development that an organism undergoes before reaching sexual maturity. During this time,the organism is not yet capable of reproduction. In humans,this phase lasts from birth up to $12$ to $13$ years of age.