Question
Part 2: Open Response
OPEN RESPONSE Question #1: Population Dynamics
The western snowy plover is a small bird that makes its nest in the sand on ocean and river shores. The snowy plover’s breeding season is from March to September. A plover typically lays three eggs each year. If disturbed, it will often abandon its nest. A snowy plover and its nest are shown below.
A. Compare the birth rate (number of eggs hatched) to the death rate in a population of snowy plovers that is increasing in size.
B. In an initial population of 100 snowy plovers, there were 30 births and 20 deaths in one year.
Based only on the birth and death rates given above, identify the expected size of the snowy plover population at the end of the year.
C. At the end of the year, there were actually 80 snowy plovers in the population.
Assuming there were no additional births or deaths, explain why the actual population size differed from the expected population size (hint: besides births/deaths why else would a population experience an increase/decrease in size).
D. Current efforts to conserve plover populations include building wire fences around their nests and making certain beaches off-limits to people during plover breeding season. Explain why making certain beaches off-limits during plover breeding season is a more effective conservation method than building fences around plover nests.
Record your answer to parts A-D here. Make sure to label each answer part clearly:
OPEN RESPONSE Question #1: Population Dynamics
The western snowy plover is a small bird that makes its nest in the sand on ocean and river shores. The snowy plover’s breeding season is from March to September. A plover typically lays three eggs each year. If disturbed, it will often abandon its nest. A snowy plover and its nest are shown below.
A. Compare the birth rate (number of eggs hatched) to the death rate in a population of snowy plovers that is increasing in size.
B. In an initial population of 100 snowy plovers, there were 30 births and 20 deaths in one year.
Based only on the birth and death rates given above, identify the expected size of the snowy plover population at the end of the year.
C. At the end of the year, there were actually 80 snowy plovers in the population.
Assuming there were no additional births or deaths, explain why the actual population size differed from the expected population size (hint: besides births/deaths why else would a population experience an increase/decrease in size).
D. Current efforts to conserve plover populations include building wire fences around their nests and making certain beaches off-limits to people during plover breeding season. Explain why making certain beaches off-limits during plover breeding season is a more effective conservation method than building fences around plover nests.
Record your answer to parts A-D here. Make sure to label each answer part clearly:
Answers
GPT-4o mini
### A. Compare the birth rate (number of eggs hatched) to the death rate in a population of snowy plovers that is increasing in size.
In a population of snowy plovers that is increasing in size, the birth rate must be higher than the death rate. This means that more individuals are being born and surviving than individuals dying. The birth rate reflects the number of eggs that successfully hatch and result in fledged young, while the death rate encompasses the individuals that are not surviving. For instance, if the population is notably growing, the successful hatching of eggs and the survival of those chicks must supersede the number of adults and chicks lost to death.
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### B. In an initial population of 100 snowy plovers, there were 30 births and 20 deaths in one year. Based only on the birth and death rates given above, identify the expected size of the snowy plover population at the end of the year.
To calculate the expected size of the snowy plover population at the end of the year, we start with the initial population and adjust it based on the number of births and deaths:
Initial population: 100
Births: 30
Deaths: 20
Expected population size at the end of the year = Initial population + Births – Deaths
= 100 + 30 - 20
= 110
The expected size of the snowy plover population at the end of the year is 110.
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### C. At the end of the year, there were actually 80 snowy plovers in the population. Assuming there were no additional births or deaths, explain why the actual population size differed from the expected population size.
The actual population size of 80 snowy plovers differed from the expected size of 110 likely due to factors other than births and deaths that can affect population size. One potential explanation is immigration or emigration. If some snowy plovers left the area (emigration) for reasons such as seeking better resources, nesting sites, or due to disturbances in their habitat, it would lower the overall population size even if the initial births and deaths remained the same. Additionally, environmental factors or human activities could have influenced the population dynamics, leading to more plovers abandoning nests, thereby reducing the number of successful fledglings.
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### D. Current efforts to conserve plover populations include building wire fences around their nests and making certain beaches off-limits to people during plover breeding season. Explain why making certain beaches off-limits during plover breeding season is a more effective conservation method than building fences around plover nests.
Making certain beaches off-limits during the breeding season is more effective than just building fences around nests for several reasons. First, restricting access to these areas reduces human disturbance, which is a significant threat to nesting success for snowy plovers. Abandonment of nests due to disturbances can significantly increase mortality rates among eggs and chicks.
Second, by closing off entire beaches, plovers can nest in a broader area without the risk of being disturbed, increasing the likelihood of successful hatching and fledging across multiple nests rather than focusing only on those that may be protected by fences.
Moreover, protected areas can create a more conducive environment for the birds, allowing them to adapt and thrive in their natural habitat without the pressure of human interference. This holistic approach not only helps in nesting success but also contributes to the overall health of the ecosystem they inhabit, thereby fostering a more sustainable and resilient plover population in the long term.
In a population of snowy plovers that is increasing in size, the birth rate must be higher than the death rate. This means that more individuals are being born and surviving than individuals dying. The birth rate reflects the number of eggs that successfully hatch and result in fledged young, while the death rate encompasses the individuals that are not surviving. For instance, if the population is notably growing, the successful hatching of eggs and the survival of those chicks must supersede the number of adults and chicks lost to death.
---
### B. In an initial population of 100 snowy plovers, there were 30 births and 20 deaths in one year. Based only on the birth and death rates given above, identify the expected size of the snowy plover population at the end of the year.
To calculate the expected size of the snowy plover population at the end of the year, we start with the initial population and adjust it based on the number of births and deaths:
Initial population: 100
Births: 30
Deaths: 20
Expected population size at the end of the year = Initial population + Births – Deaths
= 100 + 30 - 20
= 110
The expected size of the snowy plover population at the end of the year is 110.
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### C. At the end of the year, there were actually 80 snowy plovers in the population. Assuming there were no additional births or deaths, explain why the actual population size differed from the expected population size.
The actual population size of 80 snowy plovers differed from the expected size of 110 likely due to factors other than births and deaths that can affect population size. One potential explanation is immigration or emigration. If some snowy plovers left the area (emigration) for reasons such as seeking better resources, nesting sites, or due to disturbances in their habitat, it would lower the overall population size even if the initial births and deaths remained the same. Additionally, environmental factors or human activities could have influenced the population dynamics, leading to more plovers abandoning nests, thereby reducing the number of successful fledglings.
---
### D. Current efforts to conserve plover populations include building wire fences around their nests and making certain beaches off-limits to people during plover breeding season. Explain why making certain beaches off-limits during plover breeding season is a more effective conservation method than building fences around plover nests.
Making certain beaches off-limits during the breeding season is more effective than just building fences around nests for several reasons. First, restricting access to these areas reduces human disturbance, which is a significant threat to nesting success for snowy plovers. Abandonment of nests due to disturbances can significantly increase mortality rates among eggs and chicks.
Second, by closing off entire beaches, plovers can nest in a broader area without the risk of being disturbed, increasing the likelihood of successful hatching and fledging across multiple nests rather than focusing only on those that may be protected by fences.
Moreover, protected areas can create a more conducive environment for the birds, allowing them to adapt and thrive in their natural habitat without the pressure of human interference. This holistic approach not only helps in nesting success but also contributes to the overall health of the ecosystem they inhabit, thereby fostering a more sustainable and resilient plover population in the long term.