Consider an ecological network consisting of activities as nodes, with each node having an efficiency of 4 percent. The entire network is run by 1000 W of sunlight, which is converted to useful products by one node. The waste from this node is used as a resource by another node, and so on. The mature ecological network consists of 500 nodes. 

1. Calculate the energy efficiency of this network. 

2. If 50 nodes are eliminated owing to a disruption, what will be the network efficiency? 

3. Calculate the efficiency if 200 nodes are eliminated. 

4. What do these results imply about the removal of species from an ecosystem due to local extinction?