How many mass extinctions have occurred since the origin of life on Earth?

If the current rate of species extinction continues,what percentage of all species on Earth will become extinct within the next $100$ years (in $\%$)?

The impacts of loss of biodiversity may lead to:
$I$. Lowered resistance to environmental perturbation
$II$. Decrease in plant production
$III$. Increased variability in ecosystem processes like water use,pest/disease cycle,and plant productivity
$IV$. Increase in plant production
Choose the correct option.

Why is the conservation of biodiversity considered an international issue?

According to $IUCN$,when a taxon is facing an extremely high risk of extinction in the immediate future,it is categorized as:

In the last $500$ years,$784$ species have gone extinct,out of which .............. species of vertebrates were extinct.