Transport Layer
The transport layer is responsible for overseeing both error control and flow control at the source to destination level. It is the fourth layer in the OSI model and is responsible for end-to-end delivery of data between hosts. The transport layer provides reliable and ordered delivery of data packets from the source to the destination.

Error Control
Error control refers to the techniques used to ensure that data is transmitted without errors or loss. The transport layer performs error control by using error detection and correction mechanisms such as checksums and acknowledgment mechanisms. When data is transmitted, the transport layer adds a checksum to the data packet. The receiver then checks the checksum to detect any errors. If errors are detected, the receiver can request the sender to retransmit the data.

Flow Control
Flow control is the process of managing the rate of data transmission between the sender and receiver to prevent data overflow or loss. The transport layer performs flow control by using techniques such as buffering, congestion control, and acknowledgment mechanisms. It ensures that the receiver can handle the data being sent by the sender and prevents data loss due to congestion.

Other Layers
- Physical Layer: The physical layer is responsible for the transmission of raw bitstream over the physical medium. It deals with the electrical, mechanical, and physical aspects of data transmission.
- Data Link Layer: The data link layer is responsible for the reliable transmission of data frames between adjacent nodes over a physical medium. It provides error detection and correction at the link level.

Conclusion
The transport layer is responsible for overseeing both error control and flow control at the source to destination level. It ensures reliable and ordered delivery of data packets while detecting and correcting errors and managing the rate of data transmission to prevent data loss or overflow.