Based on the fossil record, average lifetime of a species before it either becomes extinct or evolves into daughter species (like say mammoth to elephant or sabretooths to modern tigers etc.) is about 5 million years = 5*10^6 years. The speciation event itself takes 0.5 to 1 million years.
https://phys.org/news/2011-08-fast-evolutionary-million-years.html
Current number of species on earth is 8 million =
8*10^6 species (
this is a low estimate). Species distribution see below, (
for animals which are about 50% of the total, rest are plants and fungi). Insects and spiders/scorpions comprise 80% of all animal species and all vertebrates(fish to mammal) form only about 5%.
On average then, we have a complete turnover of 8*10^6 species in about 5 million years (its of course staggered and occurs gradually over 1 million year frame on average). We have 550 million years since Cambrian. So there would be (again taking crude average) 110 such turnovers. Hence total number of species = 110*8*10^6= 880*10^6=
8.8*10^8 species overall.
So living species form (8*10^6)/(880*10^6)= 0.009=0.9% of total species since Cambrian. Thus we get the rough figure that 99% of all species on earth have become extinct. Depending on the estimate of current species (
that has historically varied widely), the total species count also varies.
Since speciation occurs over a million year frame (from regional variation to subspecies to partial to full reproductive isolation) one can only expect to see
a) The few cases of rapid speciation that do occur
b) The various stages of speciation that one expects in accordance to the theory of evolution.
Both cases are present
Darwin was Right | Evidence from observed speciation
Further, every ring species and subspecies (like giraffe
1 Long Neck, 4 Species: New Giraffe Diversity Revealed) are predicted examples of ongoing slow speciation.
But lets make a generous estimate and say that 10% of total speciation occurs fast enough (a century or so) to leave a trace in history. This 10% is spread over 5 million years. So
expected speciation that can be observed over any given century = 0.5*100*0.1*8*10^6/(5*10^6)=
8 observable speciation events among animals. Of this 80% i.e. 7 events will be in the insect world while just 5% i.e.
less than 1 will be among the vertebrates.
Of course the kind of evolution you want.
Class to Class happens over far far longer periods of time. There are only about
100 classes of animals in the world and classes are very long lived. Total number of classes in history of life are no more than 300 and evolution from one class to another occurs over 50-100 million year ranges.
List of animal classes - Wikipedia
I am enjoying your replies. 
