. The organelles which are termed semi-autonomous in nature are

The organelles that are termed semi-autonomous in nature are mitochondria and chloroplasts.

Step 1: Understanding the term "semi-autonomous" Semi-autonomous means that these organelles can partially self-regulate and operate independently of the cell. They have their own DNA and can replicate independently of the cell in which they are found.

Step 2: Identifying the organelles The two main organelles that are semi-autonomous are the mitochondria and chloroplasts.

Step 3: Understanding the role of these organelles Mitochondria are responsible for producing energy for the cell through the process of cellular respiration. Chloroplasts, found in plant cells, are responsible for photosynthesis, the process by which light energy is converted into chemical energy.

Step 4: Understanding why they are semi-autonomous Both mitochondria and chloroplasts contain their own DNA, separate from the DNA found in the cell nucleus. This allows them to replicate independently of the cell. This is believed to be a result of an early form of symbiosis, where an ancestral cell engulfed a smaller cell, which then became an organelle within the larger cell. Over time, most of the engulfed cell's genes were transferred to the host cell's nucleus, but some remained, allowing the organelle to retain a degree of autonomy.