Question

Almost all cacti are native to the Americas, but there is a small, relatively uncommon group of plants closely related to cacti native to tropical western Africa. How can we explain this given the information in this chapter?
A) The plants might have floated across the Atlantic
B) This might have been caused by divergent evolution.
C) The continents were once connected.
D) All of the above are true.

Answer 1

Answer:

C) The continents were once connected.

Explanation:

All the continents were once part of the super-continent called Pangaea. Continental drift split it into fragments and led to the formation of the present-day continents. Since all the continents were connected, some of the cacti native to tropical western Africa must have been carried to present-day America.

The cacti populations present in America and tropical western Africa accumulated genetic variations to get adapted to the prevailing environmental conditions. Separation of continents by continental drift led to their geographical isolation and prevented any interbreeding between the populations. Over generations, the cacti present in two continents evolved into separate species.