The parameter(s) of senescence or old age is / are -

Options

A. End of the reproductive phase
B. Concomitant change in body (like slowing metabolism)
C. Failure of metabolism decreases
D. a and b

Answer

To answer the question regarding the parameters of senescence or old age, we can break down the information provided in the video transcript into a structured solution.

### Step-by-Step Solution:

1. **Understanding Senescence**: Senescence refers to the process of aging in organisms, which is characterized by a gradual decline in biological functions and the ability to adapt to metabolic stress.

2. **Phases of Life Cycle**: The life cycle of an organism can be divided into three main phases:
- **Vegetative Phase**: This is the growth phase where the organism develops and matures.
- **Reproductive Phase**: This phase involves the ability to reproduce and is marked by the peak of biological functions.
- **Senescent Phase**: This is the phase of old age, which begins after the reproductive phase has ended.

3. **End of the Reproductive Phase**: The end of the reproductive phase is a significant marker that indicates the onset of old age. After reproduction ceases, the organism enters the senescent phase.

4. **Concomitant Changes in the Body**: As organisms age, they undergo various physiological changes:
- **Slowing Metabolism**: Metabolic processes slow down, leading to decreased energy levels and efficiency.
- **Structural Changes**: There are notable changes in body structure, such as:
- Reduction in the size of organs (e.g., ovaries).
- Decreased hair growth, often leading to greying.
- Muscle weakness and loss of muscle mass.

5. **Failure of Metabolism**: With aging, there is an increase in metabolic failure. The body becomes less efficient at processing nutrients and maintaining homeostasis, contributing to the overall decline in health.

6. **Conclusion**: Based on the above points, the parameters of senescence or old age include:
- The end of the reproductive phase.
- Concomitant changes in the body, such as slowing metabolism and structural changes.
- Increased failure of metabolic processes.

### Final Answer:
The parameters of senescence or old age are:
- End of the reproductive phase.
- Concomitant changes in the body (e.g., slowing metabolism, structural changes).