Without photosynthesis there would be no oxygen in our atmosphere only carbon dioxide, meaning that every living thing on this planet would be dead within probably days considering how much we already pollute our atmosphere. Only very few bacteria organisms named anaerobes would be capable of surviving, and in several million years these bacteria could mutate into humans surviving without oxygen, trust me, we've done it once before. Also, all plant life would die because they would not be able to produce glucose as food to keep themselves alive.
If there was no photosynthesis, plants and animals likely could not exist. In addition the atmosphere would have very little oxygen because photosynthesis releases a large amount of oxygen into the air. Otherwise, the Earth would be a pretty barren lifeless place without photosynthesis.
Imagine that the arable land is scarce then people will compete for land in competition will be big this means that it is more likely to be able to find smaller pieces of land for it is likely that the size of the House and farms will be small
From my understanding of what i learned from middle school a volcano erupts when it creates enough lava to explode for example if you had a balloon that you were inflating too much eventually it will explode