Conservation biologists have developed numerous approaches to protecting endangered species in fragmented habitats. In many ecosystems, carefully plan...

Let's begin by understanding the meaning of this sentence. We'll use our understanding of pause points and segment the sentence as shown - understanding and assimilating the meaning of each segment bit by bit!

Sentence Structure

• Conservation biologists have developed numerous approaches
• to protecting endangered species
• in fragmented habitats
• In many ecosystems,
• carefully planned networks
• of protected corridors
• [?] wildlife populations
• to migrate safely
• between isolated habitat patches

Understanding the Meaning

• The first sentence sets up the context:
  • 'Conservation biologists have developed numerous approaches'
    • Scientists working on conservation have come up with various methods
  • 'to protecting endangered species in fragmented habitats'
    • for protecting animals at risk of extinction
    • in habitats that have been broken up into disconnected pieces
• The second sentence gives us a specific example of one of these approaches:
  • 'In many ecosystems,'
  • in various natural environments
  • 'carefully planned networks of protected corridors'
  • systems of connected pathways that are protected
  • designed thoughtfully to link different areas
• Now here's where we need to fill in the blank:
  • 'networks of protected corridors _____ wildlife populations'
• Let's look at our choices:
  • We're choosing between different forms of the same basic verb
  • allows, has allowed, is allowing (all singular forms)
  • allow (plural form)
• What's the subject of this sentence - the thing doing the action?
  • It's 'networks' - this is what allows/allow the wildlife to move
  • 'Networks' is plural (more than one network)
  • 'of protected corridors' is just describing what kind of networks
  • this phrase tells us the networks are made up of corridors
  • but 'corridors' isn't the subject doing the action
• So we need a plural verb to match 'networks': allow is the correct choice.
• Now let's read the rest to see the complete picture:
  • 'allow wildlife populations to migrate safely between isolated habitat patches'
  • these corridor networks enable animal groups to move
  • from one separated habitat area to another
  • without danger
• The complete meaning: Conservation biologists use carefully planned corridor networks that allow animals to safely travel between habitat areas that have been separated.

Grammar Concept Applied

Subject-Verb Agreement with Prepositional Phrases

When a prepositional phrase comes between the subject and verb, the verb must still agree with the actual subject - not with nouns in the prepositional phrase. Prepositional phrases (called prepositional phrases in grammar terms) typically start with words like "of," "in," "at," "with," "from," etc.

The Pattern:

• Identify the subject (who/what is doing the action?)
• Cross out or ignore any prepositional phrases between the subject and verb
• Make sure the verb agrees with the subject

Example 1:

• The box of chocolates is on the table.
  • Subject: "box" (singular)
  • Prepositional phrase: "of chocolates" (ignore this)
  • Verb: "is" (singular) ✓

Example 2:

• The students in the classroom are working hard.
  • Subject: "students" (plural)
  • Prepositional phrase: "in the classroom" (ignore this)
  • Verb: "are" (plural) ✓

In our question:

• Networks of protected corridors allow wildlife populations to migrate...
  • Subject: "networks" (plural)
  • Prepositional phrase: "of protected corridors" (ignore this for agreement purposes)
  • Verb: "allow" (plural) ✓

The trap in this question is that "corridors" appears right before the blank, making it tempting to match the verb to "corridors." But "corridors" is just the object of the preposition "of" - it's not the subject. The actual subject is "networks," which is plural and requires the plural verb "allow."