Read the passage and answer the following questions:
Adding to the grim scenario of extinctions is the fact that more than 15,500 species world-wide are facing the threat of extinction. From a study of the history of life on earth through fossil records, we learn that large-scale loss of species like the one we are currently witnessing have also happened earlier, even before humans appeared on the scene. During the long period (> 3 billion years) since the origin and diversification of life on earth there were five episodes of mass extinction of species. How is the 'Sixth Extinction' presently in progress different from the previous episodes? The difference is in the rates; the current species extinction rates are estimated to be 100 to 1,000 times faster than in the pre-human times and our activities are responsible for the faster rates. Ecologists warn that if the present trends continue, nearly half of all the species on earth might be wiped out within the next 100 years.
Which of the following statements about ex situ conservation are correct?
A. Threatened animals and plants are taken out from their natural habitat and placed in special setting where they can be protected and given special care.
B. Many animals that have become extinct in the wild continue to be maintained in zoological parks.
C. Gametes of threatened species can be preserved in viable and fertile condition for long periods using tissue culture methods.
D. Seeds of different genetic strains of commercially important plants can be kept for long periods in seed banks.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → A, B and D only
Ex situ means “off site”. The plant or animal is protected outside its natural home. Besides zoos and botanical gardens, it now also uses methods such as cryopreservation of gametes, in vitro fertilisation, tissue culture and seed banks.
A. Threatened animals and plants are taken out from their natural habitat and placed in special setting where they can be protected and given special care. — True. This is what ex situ conservation means. Zoological parks, botanical gardens and wildlife safari parks serve this purpose.
B. Many animals that have become extinct in the wild continue to be maintained in zoological parks. — True. Such animals now survive only because of ex situ care in zoos.
C. Gametes of threatened species can be preserved in viable and fertile condition for long periods using tissue culture methods. — False. Gametes are preserved by cryopreservation (storage at very low temperature). Tissue culture is used for a different job: to propagate plants.
D. Seeds of different genetic strains of commercially important plants can be kept for long periods in seed banks. — True. Seed banks keep the genetic strains of useful crop plants safe for later use.
NCERT Extract:
How do we conserve Biodiversity? – “Ex situ Conservation– In this approach, threatened animals and plants are taken out from their natural habitat and placed in special setting where they can be protected and given special care. Zoological parks, botanical gardens and wildlife safari parks serve this purpose. There are many animals that have become extinct in the wild but continue to be maintained in zoological parks. In recent years ex situ conservation has advanced beyond keeping threatened species in enclosures. Now gametes of threatened species can be preserved in viable and fertile condition for long periods using cryopreservation techniques, eggs can be fertilised in vitro, and plants can be propagated using tissue culture methods. Seeds of different genetic strains of commercially important plants can be kept for long periods in seed banks.”