Introduction
In higher animals and plants, growth and reproduction are two fundamental processes that occur throughout their life cycle. However, it is observed that these processes are mutually exclusive events, which means that an increase in one process leads to a decrease in the other. This phenomenon is known as the trade-off hypothesis.

Explanation
The trade-off hypothesis suggests that an organism has a limited amount of energy that it can allocate towards growth and reproduction. Therefore, an increase in energy allocation towards one process will result in a decrease in energy allocation towards the other process. This is because both growth and reproduction require energy, resources, and nutrients, which are limited in availability.

Examples
In plants, the trade-off between growth and reproduction is evident in the allocation of resources towards vegetative growth or reproductive structures, such as flowers and fruits. Plants that invest more energy towards vegetative growth have a lower reproductive output, while those that invest more energy towards reproduction have lower vegetative growth.

Similarly, in animals, the trade-off between growth and reproduction is evident in the allocation of energy towards body size or reproductive structures. Animals that invest more energy towards growth have delayed reproduction or reduced reproductive output, while those that invest more energy towards reproduction have reduced growth or smaller body size.

Exceptions
While the trade-off hypothesis is generally observed in higher animals and plants, there are some exceptions. Some organisms have evolved mechanisms to overcome the trade-off by allocating energy and resources towards both growth and reproduction simultaneously. For example, some plants can produce flowers and fruits while still growing vegetatively. Some animals can also grow and reproduce simultaneously by increasing their metabolic rate and energy intake.

Conclusion
In summary, the trade-off hypothesis explains the mutual exclusivity of growth and reproduction in higher animals and plants. This phenomenon is due to the limited availability of energy, resources, and nutrients, which organisms must allocate towards either growth or reproduction. While there are exceptions, the trade-off hypothesis remains a fundamental concept in understanding the life history strategies of organisms.

Growth and reproduction are mutually exclusive events means that growth and reproduction both do not occur by the same process. Growth is a different process from reproduction in multicellular organism. Growth has nothing to do with reproduction in most of the multicellular organism. Growth occurs by increase in size and mass of the organism by mitotic division and differentiation of cell leads to perform specialised function. But reproduction is the process of formation of new progeny which are similar to their parent in most of the multicellular organism. In unicellular organism process of growth and reproduction are the same where cell division occurs, number of cell increases and this is also called reproduction. So growth and reproduction are synonymous in unicellular organism.