Understanding the Question: Endangered Species and Probability

The question asks us to find the most appropriate word to fill the blank space in a sentence about endangered species and their probability of facing a certain fate within a specific timeframe. The sentence is: "Endangered species have a fifty per cent or greater probability of ___________ within five years or two generations whichever is longer."

We need to consider the meaning of 'endangered species' and what high probability they might face within a relatively short period.

Analyzing the Options

Let's look at the meaning of each given option:

1. Distinction: This refers to a difference or contrast between similar things, or the act of distinguishing. It also means excellence or eminence. This word does not fit the context of what might happen to endangered species with a high probability.
2. Extinction: This refers to the state or process of a species, family, or larger group of organisms ceasing to exist. This is a significant concern for endangered species.
3. Complication: This refers to a circumstance that complicates something; a difficulty. While endangered species face many complications, having a 50% or greater probability of 'complication' within five years or two generations doesn't make sense in this specific context of their survival status.
4. Completion: This refers to the action or process of finishing something. This word is irrelevant to the probability faced by endangered species.

Determining the Most Appropriate Word

Endangered species are at high risk of disappearing forever. The sentence describes a high probability (fifty per cent or greater) of something happening within a certain timeframe that relates directly to their existence as a species. Out of the given options, 'extinction' is the term specifically used to describe the complete disappearance of a species.

Therefore, the phrase "probability of extinction" perfectly fits the context of a discussion about the risks faced by endangered species.

Filling the Blank

Substituting the most appropriate word, the complete sentence becomes:

Endangered species have a fifty per cent or greater probability of extinction within five years or two generations whichever is longer.

Conclusion

Based on the analysis of the meaning of the options and the context of the sentence concerning endangered species, the word 'extinction' is the only logical and appropriate choice to fill the blank.

Revision Table: Key Concepts

Let's quickly review the key terms from the question and solution:

• Endangered Species: A species which is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction.
• Extinction: The end of an organism or a group of organisms (taxon), usually a species. Once a species is extinct, it will never reappear.
• Probability: The extent to which something is probable; the likelihood of something happening or being the case.

Additional Information: Related Conservation Terms

Understanding conservation status helps clarify why 'extinction' is the correct word here. Conservation status indicates how likely plant, animal, or fungal species are to become extinct. Categories include:

• Least Concern (LC): Widespread and abundant taxa.
• Near Threatened (NT): Taxa that are likely to become endangered in the near future.
• Vulnerable (VU): Taxa that are at high risk of endangerment in the wild.
• Endangered (EN): Taxa that are at very high risk of extinction in the wild. (This is the category mentioned in the question).
• Critically Endangered (CR): Taxa that are at extremely high risk of extinction in the wild.
• Extinct in the Wild (EW): Taxa known only to survive in captivity or as naturalized populations well outside the past range.
• Extinct (EX): Taxa that are no longer known to exist.

The question specifically discusses the probability of moving towards the 'Extinct' category for species currently classified as 'Endangered'.