All of these represent something called "competition and predation", in which the species competes for strength, or when one species coordinates attacks against a prey species, or when one species hunts another.
The reason why there is a green layer of algae was because
of the reason that there may be too much fertilizer applied in the lawn. When
having too much fertilizer, and it had been rained down—there could have been a
possibility of run-off to be flown down on the lawn of which has been sloped
and made its way on the pond. By this, it increases the nutrients in the pond,
making the algae to grow on it.
Starch is a high molecular weight substance; therefore, it is insoluble to our cells. It needs to be broken down to simple sugars like glucose in order for it to be dissolved/absorbed in our blood. This is because simple sugars has smaller molecular weights and are more soluble.