Population Size
New individuals most commonly join a population by being born. What is this measurement called?
What is birth rate?
When individuals in a population are grouped together, like a herd of bison, this is the type of dispersion.
An environmental factor that causes a population to stop growing or decrease in size is called this.
What is a limiting factor?
This term describes the largest population size that an environment can support long-term.
What is carrying capacity?
Weather, floods, and fires are all examples of this type of population-limiting factor.
What are density-independent factors?
This term describes individuals moving INTO a population from somewhere else.
What is immigration?
When individuals are spread evenly apart at consistent distances, like penguins nesting, this is the type of dispersion.
What is Uniform Dispersion?
Climate, space, and food/water availability are all examples of this.
What are limiting factors?
This measurement tells you the number of individuals living in a specific unit of area.
What is population density?
Food shortages and disease that spread more easily in crowded populations are examples of this type of limiting factor.
What are density-dependent factors?
This term describes individuals LEAVING a population.
What is Emigration?
In this type of dispersion, where each individual's location has nothing to do with where others are found.
What is Random Dispersion?
When food and water become scarce, organisms may respond by doing this, which reduces a population's size.
What is emigrating / leaving the area?
On a logistic growth curve, the population levels off and stabilizes around this value.
What is the carrying capacity?
Unlike density-dependent factors, these reduce a population by the same proportion regardless of how many individuals are present.
What are density-independent factors?
If birth rate is greater than death rate, what happens to the population size?
What is it increases?
A dense flock of flamingos packed tightly together would be classified as this type of dispersion.
What is clumped dispersion?
This type of population growth produces a J-shaped curve where the growth rate is proportional to the current number of individuals — and has no limits.
What is Exponential Growth?
On a population graph, when birth rate and immigration rate EQUAL death rate and emigration rate, this is what happens to population size.
What is it stays the same / stabilizes?
Between 1995 and 1999, the Ormia fly population declined because fewer male field crickets could sing. Explain the cause-and-effect chain that led to the fly decline.
Fewer singing crickets → fewer crickets found by flies → less food for fly larvae → fly population decreased. (Density-dependent / food limitation.)
This long-term trend involves BOTH birth and death rates declining over time, causing a shift in the age structure of a population.
What is demographic transition?
This is the biological reason why perfect uniform dispersion is rarely observed in nature.
What is that animals are constantly moving (so spacing can never stay perfectly equal)?
Unlike exponential growth, this type of growth produces an S-shaped curve because one or more environmental factors slow the population as it gets larger.
What is logistic growth?
A graph shows a mammal introduced to an island in 1957 whose population peaked around 700 in 1975 then fluctuated around 500 through the 1980s and 1990s. What does this pattern tell us about 500 on this graph?
What is it represents the carrying capacity of the island?
In the snowshoe hare and lynx data, hare populations peak and crash on a roughly 10-year cycle. Using both density-dependent factors AND predator-prey relationships, explain why BOTH populations fluctuate together.
High hare numbers → more food for lynx → lynx population rises → more predation on hares → hare population crashes → less food for lynx → lynx decline → hare population recovers. Both density-dependent food limits and predation drive the cycle.