Panel 1 of a diagram shows an ancestral marsupial stock at the centre with lines radiating to marsupial mole, sugar glider, koala, kangaroo and Tasmanian tiger cat. Panel 2 pairs some Australian marsupials with placental mammals that resemble them, such as the Tasmanian wolf with the placental wolf and the flying phalanger with the flying squirrel. What do the panels illustrate?
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Evolution of different marsupials from one ancestral stock within Australia is adaptive radiation. When more than one adaptive radiation occurs in an isolated area, as with placental mammals there, look-alike forms arise and this is called convergent evolution.
- B.
Panel 2 shows unrelated lineages becoming alike, which is convergence.
- C.
Placental and marsupial look-alikes evolved their similarity independently.
- D.
The labels are reversed: radiation from one ancestor is adaptive radiation.
NCERT: Class 12 Biology, Chapter 6, 6.4