Question

endangered species - are species whose population:

• has been reduced by
• within 10 years or more than three generations
• occupies an extent of occurrence of less than 5,000 km2 (1,930 mi2) or area of occupancy 500 km2 (193 mi2)
• with of occupation or continuing decline in habitat area or quality
• has less than 2,500 mature adults
• with a projected continuing decline of 20 percent

Explanation:

To answer questions related to endangered species' population criteria, we refer to the IUCN Red List criteria (a key framework in conservation biology, part of the Natural Science - Biology subfield).

For the first dropdown ("has been reduced by"):

The IUCN criteria for population reduction state that a species is endangered if its population has been reduced by 50% or more within 10 years or three generations (whichever is longer). This is a core criterion for assessing population decline in endangered species.

For the second dropdown ("with [ ] of occupation or continuing decline..."):

The IUCN criteria for habitat decline (area of occupancy or quality) specify that a species is endangered if it has a continuing decline (e.g., due to habitat loss, degradation) in its area of occupancy or quality. The phrase here fits the criterion of a "continuing decline" in habitat - related metrics (area or quality) alongside the other population - based criteria (e.g., <2,500 mature adults, population reduction).

Final Answers (Filling the Blanks):

• First blank (population reduction): $\boldsymbol{50\%}$ (or "50 percent" depending on formatting; the key is the 50% reduction within 10 years/3 generations).
• Second blank (habitat decline): $\boldsymbol{continuing\ decline}$ (matches the IUCN criterion for ongoing habitat loss/quality reduction).

(Note: If the dropdowns have specific options, the most accurate IUCN - based answers for these blanks are "50%" (for population reduction) and "continuing decline" (for habitat - related decline), as these align with the standard endangered species assessment criteria.)

Answer:

To answer questions related to endangered species' population criteria, we refer to the IUCN Red List criteria (a key framework in conservation biology, part of the Natural Science - Biology subfield).

For the first dropdown ("has been reduced by"):

The IUCN criteria for population reduction state that a species is endangered if its population has been reduced by 50% or more within 10 years or three generations (whichever is longer). This is a core criterion for assessing population decline in endangered species.

For the second dropdown ("with [ ] of occupation or continuing decline..."):

The IUCN criteria for habitat decline (area of occupancy or quality) specify that a species is endangered if it has a continuing decline (e.g., due to habitat loss, degradation) in its area of occupancy or quality. The phrase here fits the criterion of a "continuing decline" in habitat - related metrics (area or quality) alongside the other population - based criteria (e.g., <2,500 mature adults, population reduction).

Final Answers (Filling the Blanks):

• First blank (population reduction): $\boldsymbol{50\%}$ (or "50 percent" depending on formatting; the key is the 50% reduction within 10 years/3 generations).
• Second blank (habitat decline): $\boldsymbol{continuing\ decline}$ (matches the IUCN criterion for ongoing habitat loss/quality reduction).

(Note: If the dropdowns have specific options, the most accurate IUCN - based answers for these blanks are "50%" (for population reduction) and "continuing decline" (for habitat - related decline), as these align with the standard endangered species assessment criteria.)