The last twenty years or so have witnessed the disappearance of at least

(1) 27 species

(2) 40 species

(3) 12 species

(4) 7 species

(1) Some groups like fishes appear to be more vulnerable to extinction

(2) More than 15500 species world-wide are facing the threat of extinction

(3) Presently, 12 per cent of all bird species in the world face the threat of extinction.

(4) Both B and C

(1) Birds-12 per cent

(2) Mammals- 23 per cent

(3) Amphibians- 27 per cent

(4) Gymnosperms- 31 per cent

(1) Large scale of loss of species have happened earlier even before humans appeared on Earth

(2) Large scale of loss of species have happened earlier within 1000 years of human evolution

(3) Large scale of loss of species have happened earlier just after humans appeared on Earth

(4) Large scale of loss of species have happened within 100 years of human evolution.

(1) 5th

(2) 6th

(3) 4th

(4) 7th

(1) a- more than three billion years

(2) a- more than 4.5 billion years

(3) b- six extinctions

(4) Both A and C

1. Difference in the rates

2. Current rate is 100-1000 times faster than previous episodes

3. Human intrusions

4. Extinction of special bird species

(1) Nearly half of all the species on Earth can be wiped out within the next 100 years

(2) Nearly one fourth of all the species on Earth can be wiped out within 200 years

(3) Nearly one eighth of all the species on Earth can be wiped out within 100 years

(4) Nearly one third of all the species on Earth can be wiped out within 200 years

(1) Decline in plant production

(2) Lowered resistance to environmental perturbations such as drought

(3) Increased variability in certain ecosystem processes such as Plant Productivity

(4) Decreased variability in certain ecosystem processes such as pest and disease cycle

(1) Habitat loss and Fragmentation

(2) Dosage compensation

(3) Alien Species Invasions

(4) Co-extinctions