Consider the following statements about species diversity and the ecosystem:
I. Loss of biodiversity in a region may lower its resistance to environmental perturbations such as drought.
II. Loss of biodiversity in a region may lead to a decline in plant production.
III. Loss of biodiversity in a region may increase variability in ecosystem processes such as plant productivity, water use, and pest and disease cycles.
IV. Tilman found that plots with more species showed more year-to-year variation in total biomass.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → I, II and III
Species diversity keeps an ecosystem stable and productive. When a region loses many species, its plant production, its resistance to disturbance and the steadiness of its processes can all suffer.
I. Loss of biodiversity in a region may lower its resistance to environmental perturbations such as drought. — True. A region with fewer species is less able to withstand disturbances such as drought.
II. Loss of biodiversity in a region may lead to a decline in plant production. — True. Fewer species usually means lower plant production. Tilman's experiments showed that more diversity gave higher productivity.
III. Loss of biodiversity in a region may increase variability in ecosystem processes such as plant productivity, water use, and pest and disease cycles. — True. With fewer species, these processes become less steady from year to year.
IV. Tilman found that plots with more species showed more year-to-year variation in total biomass. — False. Tilman found the opposite: plots with more species showed less year-to-year variation in total biomass.
NCERT Extract:
The Importance of Species Diversity to the Ecosystem – “… David Tilman’s long-term ecosystem experiments using outdoor plots provide some tentative answers. Tilman found that plots with more species showed less year-to-year variation in total biomass. He also showed that in his experiments, increased diversity contributed to higher productivity.”
Loss of Biodiversity – “… In general, loss of biodiversity in a region may lead to (a) decline in plant production, (b) lowered resistance to environmental perturbations such as drought and (c) increased variability in certain ecosystem processes such as plant productivity, water use, and pest and disease cycles.”