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The Temperate Deciduous Forest: Population Growth


Alyssa Nucci
AP-Biology
The Temperate Deciduous Forest: 
Population Growth 


Exponential Growth: 

       Exponential growth is growth where the rate increases faster than the growing total number or size. This type of growth occurs when a population is increasing without any limiting factors. An exponential graph rises in a "J" curve from the lower left to the upper right. In the Temperate Deciduous Forest, an example of an organism of exponential growth is bacteria. In this biome, the medium provides the nutrients necessary for bacteria's growth. There are four stages to the exponential growth of these bacteria. Once bacteria enter the ecosystem, there is a period of time called the lag phase, where the population size remains constant. Next comes the log phase, where cell numbers increase in an exponential growth pattern. This phase continues until nutrients are expended, causing the cell growth rate to slow, and the bacteria enters the stationary phase. Here, the size of the population remains constant as cells begin to die. Last comes the death phase, in which the rate of the death of cells is higher than the formation of new cells.
Logistic Growth and Carrying Capacity: 

       Logistic growth is when a population's growth rate gets smaller and smaller as the population size approaches a maximum determined by limited resources in the environment (carrying capacity). A logistic graph produces an "S" shaped curve. In this type of growth, exponential growth continues until the population number gets large enough to the point that resources are used up. At this point the growth rate begins to slow, and eventually plateau, making the "S" shape of the graph. At this plateau the population size levels off, representing the maximum population size the environment can support, called the carrying capacity. An example of an organism that grows at a logistic rate is the white-tailed squirrel. This organism is an R-selected species, meaning its population continues to grow until they reach their maximum reproductive capacity. This species grows at an exponential rate until resources are no longer available, leveling the population at the carrying capacity. 
Age-Structured Pyramids: 


       An age-structure pyramid shows the chance each age group has of surviving in a population. This pyramid is a graph that conveys and evaluates a population fitting any of three categories. The first category is expansive, which is made up of a younger population and is growing. This type of population often has high fertility rates and lower life expectancies. An expansive population in the Temperate Deciduous Forest would include R-selected species like the white-tailed squirrel, Eastern chipmunk, and the carpenter bee. The next category is constrictive, which is made up of an elderly population and is shrinking. This type of population has higher levels of development, where access to resources is available to a large portion of the population. K-selected species like the American black bear, red fox, and white-tailed deer have a constrictive population. The last category is stationary, which has little to no population growth. This type of population has low birth rates and an overall high quality of life. An example of an organism with a stationary population is the panda, which has very slow birth rates. 


 Boucher, Lauren. “What Are the Different Types of Population Pyramids?” Population Education, 19 Feb. 2019, populationeducation.org/what-are-different-types-population-pyramids/.

“Exponential & Logistic Growth.” Khan Academy, Khan Academy, www.khanacademy.org/science/biology/ecology/population-growth-and-regulation/a/exponential-logistic-growth.

 “Growth of Bacterial Populations.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., www.britannica.com/science/bacteria/Growth-of-bacterial-populations.

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