Which of the following pairs gives two attributes of a stable community?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Resistance to invasions by alien species and resilience to disturbances
Ecologists have long held that communities with more species tend to be more stable. A stable community has three attributes: it shows little variation in productivity from year to year, it is resistant or resilient to occasional disturbances, and it is resistant to invasions by alien species.
Option (1) High productivity and resistance to invasions by alien species — Incorrect. Resistance to invasions by alien species is an attribute of a stable community, but high productivity is not. The book asks only that productivity should not vary too much from year to year.
Option (2) High productivity and resilience to disturbances — Incorrect. Resilience to disturbances is an attribute, but high productivity is not one of the attributes listed for stability.
Option (3) Resistance to invasions by alien species and resilience to disturbances — Correct. Both parts are attributes of a stable community: it must be resistant to invasions by alien species, and it must be resistant or resilient to occasional disturbances, natural or man-made.
Option (4) Resistance to invasions by alien species and low productivity — Incorrect. Resistance to alien species is right, but low productivity is not an attribute of stability. A stable community keeps its productivity steady, without large swings.
NCERT Extract:
The Importance of Species Diversity to the Ecosystem – “… For many decades, ecologists believed that communities with more species, generally, tend to be more stable than those with less species. … A stable community should not show too much variation in productivity from year to year; it must be either resistant or resilient to occasional disturbances (natural or man-made), and it must also be resistant to invasions by alien species.”