Question

black-footed ferrets live in the great plains of the united states. prairie dogs are their main source of food. changes in land use from grasslands to agriculture in the 1900s resulted in a decline in prairie dogs. plague (yersinia pestis) and programs to eradicate prairie dogs also severely reduced prairie dog populations, subsequently driving the black-footed ferret to the brink of extinction. conservation measures to increase the number of black-footed ferrets emphasize the health of their prey, the prairie dogs.

determine if the given factors provide top-down regulation or bottom-up regulation of prairie dogs.

top-down regulation
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bottom-up regulation
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answer bank
wet year resulting in an increase in grass for forage
predation by ferrets, coyotes, and hawks
land use change from agriculture to grassland
eradication by humans
infection with plague

Explanation:

To solve this, we first recall the definitions:

• Top - down regulation: Control of a population by predation, disease, or human - induced removal (factors from higher trophic levels or external biotic/anthropogenic factors affecting the population).
• Bottom - up regulation: Control of a population by the availability of resources (like food, habitat) from lower trophic levels or the environment.

Step 1: Analyze each factor for Top - down regulation

• Predation by ferrets, coyotes, and hawks: Predators (higher trophic level) eat prairie dogs, so this is top - down.
• Eradication by humans: Humans (external agent) remove prairie dogs, so this is top - down.
• Infection with plague: Disease (biotic factor) affects prairie dog population, so this is top - down.

Step 2: Analyze each factor for Bottom - up regulation

• Wet year resulting in an increase in grass for forage: Grass is a resource (food for prairie dogs, lower trophic level) that increases, so this is bottom - up.
• Land use change from agriculture to grassland: Grassland is the habitat and resource (food source) for prairie dogs, so this is bottom - up.

Final Categorization

• Top - down regulation: predation by ferrets, coyotes, and hawks; eradication by humans; infection with plague
• Bottom - up regulation: wet year resulting in an increase in grass for forage; land use change from agriculture to grassland

Answer:

• Top - down regulation: predation by ferrets, coyotes, and hawks; eradication by humans; infection with plague
• Bottom - up regulation: wet year resulting in an increase in grass for forage; land use change from agriculture to grassland