Answer:
Schleiden had even supposed the nucleus to be a constituent part of the wall, sometimes lying enclosed between two layers of its substance, and Schwann quoted this view with seeming approval. Schwann believed, however, that in the mature cell the nucleus ceased to be functional and disappeared.
Answer:
Option A, Key stone
Explanation:
A keystone species plays a major role in an ecosystem as it is the species whose presence effects all other species in the ecosystem .In general a keystone species is always a dominant predator that feed on prey population. If it is removed, the prey population will explode and the population diversity will reduce. For example - bison, prairie dog etc.
Hence, option A is correct
