Two snails belong to the same species. Yellow shelled snails found in grassland areas, dark shelled ones in woodland. Shell colour determined by genes. Explain how natural selection could have caused this distribution of snails

The yellow banded shell provides camouflage to the snail in grassland areas. These are more difficult for the birds to see, so less are eaten by predation. As a consequence, more yellow banded snails survive and go on to reproduce. The gene for the yellow banded shell will be passed on to the offspring.