They represent every dead soldier in the wars.
They don't
Poppies were the only plants that grew in the ravaged fields of World War I. John McCrae wrote a poem "In Flanders Field" after being inspired by the poppies growing in the battlefield, and when the poem was published, poppies became associated with remembering the soldiers who gave their lives.
In the runup to Rembrance Day, 11th November, we wear poppies to represent the fact that after World War One, the only thing that grew in the war fields was poppies.
Mekon was mortal, but poppies represent the goddess Demeter as the bringer of sleep or death. Poppies were used in Greco-Roman myths as offerings to the dead: a second meaning of the depiction and use of poppies in the Greco-Roman myths is the symbolism of the bright scarlet colour as signifying the promise of resurrection after death.
Because Mekon, a man loved by the goddess Demeter was metamorphosed into a poppy flower.
Red symbolizes the blood of the fallen soldiers, black is the grief over them, and green is the hope.
The Queen is Queen of many independent Kingdoms (Realms/Dominions). She is not only a British Monarch but also an Australian/Canadian Monarch. She wears four poppies to honor those who have died in war. The wearing of poppies for this reason comes from the poem "In Flanders Fields," which has particular significance in Canada.
Because they represent poppies from Flanders in Belgium. In this particular region thousand of lives were lost during the first world war. Poppies grew in the fields after the war. So the poppies don't directly represent the fighting at Gallipoli but are used to remember the dead from all of WW1
The significance is that the shell used to represent organisation, the glasses (piggy's specs) represent hope, without them, there would be no fire.
Daffodils, violets and poppies all belong to the phylum Angiospermae, also known as Magnoliophyta. Angioserms represent all of the flowering plants. The next step down in classification (taxonomy) shows the daffodil to be a moncot and the violets and poppies are dicots, so they can't all be grouped together here.
A collective noun for poppies is a field of poppies.