The word phase means to change a part of a development
They can be described through GENOTYPE because dominant always shows through phenotype.
The species was a keystone species.
Keystone species are the species that ''hold the ecosystem together''.
They have an important role in the trophic networks (food chains) and often they can even afflict changes in the abiotic part of the ecosystem (change the composition of soil, purify the water, lower the effect of the wind etc)
Therefore, when a keystone species is removed it affects greatly the whole ecosystem.
The correct characteristic of the Ascomycota is definitely C. Sac formation, because they produce <span>microscopic spores inside sacs. I am pretty sure that this answer will help you. Regards!</span>