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Exam 2 - Ecology

  • Levins's metapopulation model: a population will persist for a long time if its patch colonization rate (\(c\)) is greater than its patch extinction rate (\(e\)). A population goes extinct if the extinction rate exceeds the colonization rate. \

  • Polar bears are found in the Arctic but not in Antarctica is because polar bears, which were derived from brown bears that lived in the Northern Hemisphere, are either unable or unwilling to travel across the tropical areas that lie between the Arctic and Antarctica. 

  • Continental drift: the movement of the Earth's continental plates over geological time, which has played a significant role in shaping the distribution of species and their habitats across different regions. This process has led to the isolation of populations and the emergence of unique species as environmental conditions change.

  • Which population would be expected to remain stable in size?

    • A population with an r of > 0

  • As a population approaches its carrying capacity, the intrinsic rate of increase (r) typically decreases due to increased competition for resources, limited space, and other environmental factors.

Delayed density independence: this occurs when a population's growth is influenced by factors that depend on density with a lag time, meaning that any regulation on the population size does not immediately impact growth rates.

Carrying capacity: the maximum population size that an environment can sustain indefinitely without being degraded, determined by the availability of resources such as food, habitat, water, and other essentials.

Extinction vortex: a phenomenon where a small population experiences a decrease in genetic diversity, leading to an increased risk of extinction due to inbreeding, loss of adaptive potential, and heightened vulnerability to environmental changes.

Delayed density dependence: this results in a time lag between the increase or decrease in population size and the response of the growth rate to resource limitations, which can lead to oscillations in population dynamics.