From the diagram (see the attached image), the part of the organism that performs a function similar to the part of the cell marked with the arrow would be the brain.
The part marked with the arrow represents the nucleus of the cell.
- The basic function of the nucleus is to control all cellular activities such as reproduction, homeostasis, respiration, etc.
- The function of the brain is also to control all the physiological, reproductive, etc. activities of the organism's body.
It is then safe to infer that the nucleus of a cell and the brain of an organism are functionally similar. Hence, the part of the organism that performs a function similar to the part of the cell marked with the arrow is the brain.
More on the brain and the nucleus can be found here: https://brainly.com/question/11106069
