(1) Bio-community refers to the collection of all kinds of bio-populations gathered in a certain area at the same time, so all the components in the diagram form a bio-community.

(2) Roads and high-rise buildings block the connection between the components of the ecosystem, thus affecting the material circulation, energy flow and information transmission of the ecosystem, and being separated by roads, it produces geographical isolation.

(3) Among the n captive Pelicans, m were marked. According to the formula of population density, there were about (M×n)/m=(25×168)/7=6 in the 3hm2 nature reserve, and then it was inferred that there were 6/3 in each hm2. The introduction of new species should be cautious, because the introduced new species may lack natural enemies, which will increase the population rapidly, occupy a large number of resources, lead to ecological imbalance and reduce biodiversity.

Therefore, the answers are:

(1) biological community (community)

(2) material circulation, energy flow and information transmission (three points are indispensable)? Geographical isolation

(3)2 is greater than

(4) speed and direction? The introduced new species may lack natural enemies, which makes the population increase rapidly, encroaches on a large number of resources, and leads to ecological imbalance (biodiversity reduction).