1) There are ~1500 species of cacti in North and South American, most of whom ar
ID: 309205 • Letter: 1
Question
1) There are ~1500 species of cacti in North and South American, most of whom are superbly well adapted to live in desert environments. They vary greatly in form from giant saguaro, to prickly pears, to minute plants that look almost like pebbles. There are no cacti native to deserts in Africa or Asia, yet it has been found that many cacti thrive there when introduced by humans.
a. How can the natural distribution of cacti be explained within the framework of common ancestry?
b. Why would this pattern be hard to explain if you believed that different cacti species had originated separately?
2) There are ~300,000 species of flowering plant (angiosperms). In all cases where unambiguous single flowers carry both male organs (stamens) and female organs (pistils) the pistils are at the center of the flower and stamens are in the periphery.
a. How would this pattern be explained under the assumption that all flowering plants trace back to a common ancestor?
b. What would you need to propose if you wished to claim that actually each of the 446 angiosperm families originated separately?
Explanation / Answer
1. (a) The Cacti is capable of flourishing in any environment whether it is a wet moist atmosphere or an arid desert reason.This is because of the adaptations it underwent to survive the adverse condition present when the atmosphere was evolving. But these adaptations does not stop the plant from thriving in a favorable situation. Like it thrives in deserts of Africa and Asia despite the fact that it is not its native place.
(b) The growth pattern will be hard to explain if the plant has originated separately because, if the plant originated separately in a different environment and condition, then it means it will not thrive in a condition that is not as the condition where it originated. This is because of this reason it is not possible to believe that the Cacti has originated separately.
2. (a) According to the Darwinian theory, it is suggested that the trait if found in all the species then it suggests that the ancestor is common. This is backed by the fact the traits are selected naturally and is found in all resembling species. This is proved recently by the whole genome sequencing of the flowering plant Ambroella.
(b) If it is to be believed that each of the 446 families has originated separately that means that they will not have similar characteristics and will not thrive in conditions other than they originated. But this assumption will be contradictory as the traits and the genes are inherited and selected naturally by the process of natural selection.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.