During the late 1800s, cattle egrets arrived in South America from Africa and began to colonize. Their range has expanded dramatically over the years. Why were they able to do this?

Question

A.  The habitats that they left in Africa were not suitable for any further colonization; thus, they were forced to emigrate.
B.  The habitats that they encountered in South America were suitable to them and unoccupied.
C.  There were abundant cattle for the birds to gather around in South America; furthermore, various animals that the egrets had lived around in Africa had become quite scarce because of over hunting and poaching, causing the birds to extend their range.
D.  The food resources in South America were far superior to those in Africa, allowing the egrets more opportunity to grow and reproduce and ultimately expand their range.


Clarify question:
What is the key concept addressed by the question?

What type of thinking is required?


Gather Content:
What do you already know about what impacts the colonization of a new habitat? What other information is related to the question? 


Choose Answer:
Given what you now know, what information is most likely to produce the correct answer?


Reflection on Process:
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

B.  The habitats that they encountered in South America were suitable to them and unoccupied.


Clarify question:
What is the key concept addressed by the question?
 
You will need figure out how egrets that were adapted to life in Africa were able to successfully colonize South America.
What type of thinking is required?
This is an analyze question, you will need to break the question down into its components to determine the answer. 


Gather Content:
What do you already know about what impacts the colonization of a new habitat? What other information is related to the question? 
If a species is going to successfully colonize a new area it must be able to survive and reproduce in the new area. If a species is adapted to survive in its ancestral area, what must be true about the new area that is being colonized?


Choose Answer:
Given what you now know, what information is most likely to produce the correct answer?
The range of a population may expand either because environmental changes improve the suitability of a new region, or because a chance event allows a species to cross a barrier into a new suitable region. The relative quality of the old range has no bearing on whether the population will expand into the new region. In the example of the cattle egret, some chance crossing of the Atlantic allowed the species to arrive in South America in the 1880s, and the population has gradually expanded both northward and southward into all suitable regions.


Reflection on Process:
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
Were you able to analyze each scenario in terms of how it impacts the ability of the egret population to expand its range and what factors would be important and what factors wouldn't provide any advantages?