"It is now believed that speciation did proceed in leaps and bounds rather than just by 'creep'"

This is what I said further back in the thread. The "jumps" are sometimes referred to as "monsters".

"- the periodic wide-scale extinctions allowed exploitation by different organisms due to opening up of opportunities for slightly differing organisms to proliferate."

How does the extinction of one make any difference? The giraffe may have more opportunity to survive if one of its preditors goes extinct, or if one of its competitors for food goes extinct, but that goes absolutely nowhere in still explaining how he got his long neck.

If what you are saying is that the two events (the monster giraffe and the extinction of his competitor) happened by random chance simultaneously, well, that's yet another small example of what I was saying about the necessary complexity that must be in place for simple advancement to occur. In other words, it isn't correct to explain evolution, at any level, without acknowledging that the order/timing of the "jump" is as important as the "jump" itself.

How many times do folks laugh in derision at the Genesis creation account because, they contend, the events occur out of order for survival to have occurred?