How fast species are disappearing, and why. The mass extinctions, the four causes that ecologists call the evil quartet, and the reasons that biodiversity is worth keeping, from medicines to the right of every species to live.
3 lessons, about 1 h 25 min3 simulations11 problems3 practice questionsPython in every lesson
Created by StemPy LabSpecies have always disappeared, but now they disappear far faster than before. This lesson gives the mass extinctions, the present rate, the numbers that NCERT quotes for the extinct and the threatened species, and what the loss of species does to an ecosystem.
Ecologists name four main causes of the loss of biodiversity, the evil quartet. This lesson explains each with the examples of NCERT: habitat loss and fragmentation, over-exploitation, alien species invasions and co-extinctions, and it works out how cutting a forest into pieces destroys its core.
Why should we keep biodiversity? NCERT gives three kinds of reasons: narrow utilitarian, broad utilitarian and ethical. This lesson explains each, gives the numbers that NCERT quotes, and shows the arithmetic of the value of nature's services.
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