The blockchain is, in fact, represented as a singly linked list. Each block has a hash of the previous block - which can be thought of as a pointer to previous block.
In the blockchain each transaction in the block is stored in a Merkle Tree. But the blockchain itself is not a tree.
One of the major difference between a blockchain and a linked list is that you can't remove or add a block in the middle of the list/chain.
The way a blockchain is represented as a singly linked list. Each block has a hash of the previous block which can be thought of as a pointer to previous block.
Some differences are that in a linked list, there are generally more operations for a linked list that are not available in a blockchain, most notably being able to remove a block and to add a block in the middle of the list/chain.