The blockchain derives it’s inherent security from this chain of verifiably 100% accurate information because of the cryptography and the way it is used.
The block structure in Bitcoin is as follows
[ I found a great visualising app here LiveBlocks ]
To make it harder to change block/transaction history, making the network trustworthy by creating unique outputs through hashing linked blocks.
The way blocks are intrinsically linked to every successive block, makes backtracking the network and changing ‘any’ historical data infeasible thus creating immutability.
The structure of a block is made of the following inputs; block header(hash of previous block, current target), list of transactions contained within new block, timestamp(transaction counter), nonce, and blocksize.
The link makes it so they are tamper proof. It makes it so all past transactions are sealed like is if you were writing it on large stones like the vikings.
The block structure is determined by the hash from the previous hash. The transaction list in the the current block that make up the current hash fingerprint that is determined by the nonce.
So that is one block is altered it messes up all the blocks and the chain is rejected.
The block is made up of transactions, Hash, and the nonce.
So that even a minor change to a single block would have a domino, or butterfly effect, on All proceeding blocks in the chain. The change would throw up immediate errors and flag the change as incorrect. Its what makes it immutable. And beautiful lol!
Each block will have its own hash which was generated using the transactions within it, the pevious blocks hash, and the correct nonce.
Like most of your homework 
i opened Live blocks on the browser and find it useful. I didn’t know it. Have you signed in? Has it any difference as if you are not logged in?
Hey there, thanks! 
No I’ve not created an account there - I liked the look of it and wanted to go back and take a deeper look sometime later.
This causes changing a previous block to break the links to all following blocks. This causes a shorter chain which is then rejected by the nodes.
It contains the previous block hash, block data, and the current block hash.
Let me please know if you do so and if you see something more interesting, because i am looking on something else at this point and don’t want to confuse my head to much with many things. My regards 
I will - and yeah, exactly - it’s all about the focus - too many things on the attention = not enough retention! 
What I like about writing up coursework/homework on here is that I can download it all at the end and refer to it later. I’ve noticed that after a certain time you can’t edit your posts on here, so I’ll be ‘parking’ useful links as I come across them. Have a great day
Why is it important that the blocks are cryptographically linked together?
It ensures that past transactions cannot be altered, thus securing the network.
What does the block structure look like in bitcoin?
It consists of the transaction list in the current block, as well as the one in the previous hash, and a number (nonce) to be guessed.
2…
Version
Previous Block hash
Merkle root hash
Timestamp
Difficulty target
Nonce
Block Size
Block header
Transaction counter
Transactions
It’s important that they are linked so nobody can go back and change the transactions on the ledger, double spend, or claim that they have more bitcoin than they own.
The block structure is reward/list of transactions, previous block hash, nonce, and then the current block hash.
Because that way noone can change any data inside the chain without everybody automatically finding it out as the hashes would be different.
You have the block number, a nonce (random number), a list of all transactions (data) and the hash of the previous block. All that combined with the right input (nonce) makes the new has of the current block.
Why is it important that the blocks are cryptographically linked together?
is important that all the blocks are cryptographically linked together because in this way we ensure that all the data in the blocks are unchangeable without braking the chain, so ensure the immutability and integrity of the blockchain.
What does the block structure look like in bitcoin?
the structure is build like this: