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44.4 Regulation of Population Size
Reducing the carrying capacity is the best way to limit the growth of a pest.
Reducing the population size encourages growth.
Farmers can reduce the carrying capacity of a pest by alternating rows of different crops.
The density-independent and density- dependent factors affect population size.
Researchers discovered that a large proportion of eggs did not survive the winter and that growth never occurred.
It is possible that a low number of individuals at the start of the season helps prevent growth.
A population crash may occur if exponential growth causes population size to rise above the carrying capacity of the environment.
In 1911, 4 male and 21 female reindeer were released on St. Paul Island in the Bering Sea.
There was no hunting pressure or predator on St. Paul Island.
The herd grew to over 2,000 reindeer by 1938 and then declined to 8 animals by 1950.
Malthusian growth is a pattern of population explosion followed by a population crash.
The economist Thomas Robert Malthus had a great influence on Charles Darwin.
Ecologists know that biotic and abiotic conditions play an important role in regulating population size in natural environments.
Abiotic factors include floods and forest fires.
Natural disasters can kill individuals and lead to a reduction in population size.
Increased population density does not increase the occurrence of such an event more often than a less dense population.
The percentage of people who die is compared to the population density.
Floods do not necessarily kill a larger percentage of a dense population than of a less dense one.
The larger the population, the more affected it is.
Population density does not affect the impact of a density-independent factor.
As the density of the population increases, the intensity of competition, disease, and parasites will increase.
Not all members of the population have access to the resources necessary to ensure survival or reproduction.
Birds need a tree hole to raise their offspring.
Each pair can have a hole in which to lay eggs if there are more holes than breeding pairs.
If there are fewer holes than breeding pairs, each pair must compete to get a site.
Pairs that don't gain access to holes will not be able to contribute to the population.
Competition for food affects population growth.
Resource partitioning is a way to reduce competition for food.
The adults feed on flowers while the caterpillars eat leaves.
Parents don't compete with their offspring for food.
As the prey population grows denser, the effect of predator on the population increases.
Only 2 mice will be left out in the open if there are 100 holes and a low density of mice.
It might be difficult for the hawk to find only 2 mice.
The predation rate is zero if neither mouse is caught.
If there are 100 holes and a high density of 200 mice, the hawk will be able to find some of them.
If half of the exposed mice are caught, the rate is 50%.
Increasing the density of available prey has increased the amount of people that are preyed upon.
The density of the population has an effect on the impact of predation.
The parasites are smaller than their hosts.
parasites weaken their hosts over time.
A person who is highly parasitized is less likely to produce offspring than someone who is healthy.
Parasitism plays a role in regulating population size.
Disease is more likely to spread in a dense population due to the amount of contact between healthy individuals and people who are sick.
The population of Europe was reduced by 50% due to the Black Death in the 14th century.
Density-independent and density- dependent factors are not the same as the organisms.
The size and growth of a population can be affected byIntrinsic factors.
Intrinsic factors are based on the behavior of the organisms.
Population size and growth rates can be affected by territorial and dominance hierarchies.
The population sizes of more complex organisms are regulated by recruitment and migration.
It could be that some populations have an innate instability.
Ecologists use models to predict changes in systems.
Dungeness crab populations were assumed to have many adults and then die.
The majority of the larvae don't survive and stay close to home.
The model predicted wild fluctuations in population size without a pattern.
Population growth-regulating factors can be used as agents.
Some members of a population are more likely to survive and reproduce when certain density-independent or density- dependent factors are present in the environment.
When these factors are part of the environment, they will be more prevalent in the next generation.
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