Question about the variety of life increasing and extinctions?

Question

I was reading in a science magazine that the number of living organisms on earth has definitely increased over the past 600 million years and despite 5 mass extinctions, times when many organisms go extinct in a short time the variety of life increases. The number of living families has more than doubled in the past 250 million years and is 5 times what is was more than 50 million years ago. What does all this mean?

Answer 1

I haven't read the article, but it seems they are making the point that evolution is a constant, and somewhat cumulative process (meaning we are gaining more species than we are losing through time).  It also seems to be making the point that life is resilient--able to rapidly recover from mass extinction events in relatively short periods of time. Perhaps this is partially due to having some complex organisms surviving after mass extinctions (i.e. the slate is not wiped clean).  This is good news for the world, because we are currently undergoing massive losses of species.  This article provides hope that the world will recover once humans are done wrecking havoc on this prolific planet.  

Answer 2

Some species die or go extinct may be related with the theory of natural selection and above all evolution.

In my point of view, some other possible factors that possibly affect may be

--> lack of food supply

--> lack of suitable environment to survive

-->ecological factors

-->disease spread factors

-->genetical factors and mutations

-->competition and

-->predation

--> geographical and global climate change

But not only.

Variety of life has doubled, or trippled or increased just 5 times than before is an another theory. This phenomenon is affected by many bio-factors, such as

--> genetic factors

--> rapidly growing age structure of population

--> speciation

-->positive mutation

-->crossing over

-->positive environmental changes

-->favouring climate and temperature

-->abundance of food source

and so on.