Read the passage carefully and give the answers to the next five questions:
Does the number of species in a community really matter to the functioning of the ecosystem? This is a question for which ecologists have not been able to give a definitive answer. For many decades, ecologists believed that communities with more species, generally, tend to be more stable than those with less species. According to the International Union for Conservation of Nature and Natural Resources (IUCN) (2004), the total number of plant and animal species described so far is more than 1.5 million.
Which of the following is not a characteristic of a stable biological community?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → All the species are equally important in a stable community and absence of any one leads to its unstability.
Option (1) It must be resistant to invasions by alien species. — A characteristic of a stable biological community. Alien species can turn invasive and push out the native species, so a stable community resists them.
Option (2) It should not show too much variation in productivity from year to year. — A characteristic of a stable biological community. A stable community produces about the same amount of biomass every year.
Option (3) All the species are equally important in a stable community and absence of any one leads to its unstability. — Not a characteristic of a stable biological community. Species are not all equally important. In the rivet popper hypothesis, losing a few rivets on the seats does little harm, but losing the rivets on the wings, the key species, is a serious threat. So the loss of one species does not always make a community unstable.
Option (4) It is resilient to occasional disturbances, whether natural or man-made. — A characteristic of a stable biological community. A stable community either resists a disturbance or recovers from it quickly.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
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.”