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Logistic vs Exponential Growth
Episode 2715th February 2021 • My AP Biology Thoughts • Hopewell Valley Student Publications Network
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My AP Biology Thoughts

Unit 8 Episode #27

Welcome to My AP Biology Thoughts podcast, my name is Victoria and I am your host for episode 27 called Unit 8 Ecology: Logistic VS Exponential Growth. 

Segment 1: Introduction to Logistic and Exponential Growth

Logistic Growth: populations grow as fast it can with the limited resource it has to support the growth, making the population growth dependent on the availability of resources, when resources start to decrease or come to a stop, that is called carrying capacity

  • Exponential growth may happen for a while, if there are few individuals and many resources. But when the number of individuals gets large enough, resources start to get used up, slowing the growth rate. Eventually, the growth rate will plateau, or level off, making an S-shaped curve. The population size at which it levels off, which represents the maximum population size a particular environment can support, is called the carrying capacity, or K
  • Any kind of resource important to a species’ survival can act as a limit, causing the carrying capa For plants, the water, sunlight, nutrients, and the space to grow are some key resources. For animals, important resources include food, water, shelter, and nesting space. Limited quantities of these resources results in competition between members of the same population, or intraspecific competition (intra- = within; -specific = species).

Exponential Growth: resources are unlimited, populations grow as fast as they can, J-shaped curve, the populations faces no predators, like an invasive species

Segment 2: Example of Logistical and Exponential Growth 

Yeast (logistic growth) 

  • a microscopic fungus used to make bread and alcoholic beverages, 
  • can produce a classic S-shaped curve when grown in a test tube.
  • In the graph shown below, yeast growth levels off as the population hits the limit of the available nutrients. 
  • (If we followed the population for longer, it would likely crash, since the test tube is a closed system – meaning that fuel sources would eventually run out and wastes might reach toxic levels).

Spotted Lantern Fly (an Invasive species) or Bacteria 

  • The Spotted Lanternfly is an invasive species that destroys fruit crops, trees and plants by hopping from plant to plant, crop to crop, and tree to tree. 
  • Although native to regions in China, India, and Vietnam, it was first detected in Berks County, Pennsylvania in 2014. 
  • Since then, Pennsylvania vineyards have seen considerable damage in high infestation areas and the Mid-Atlantic states of Delaware, Maryland, New Jersey, Virginia and West Virginia have also suffered from its presence. 
  • Insecticides are effective at killing the insect on grapevines, but they are expensive and of limited use because of constant re-infestation from the Spotted Lanternfly dispersing from wild hosts to surrounding vineyards.
  • They are constantly growing due to them not having predators to kill them off, them adjusting perfectly to the environment, and are just constantly growing, spreading their home. 

Segment 3: Digging Deeper Logistical and Exponential Growth

  • Logistic and exponential growth fall into Population ecology,  the study of how populations — of plants, animals, and other organisms — change over time and space and interact with their environment. Populations are groups of organisms of the same species living in the same area at the same time. And are examples of population growth: how the size of the population is changing over time.
  •  Studying how and why populations grow or shrink, help scientists make better predictions about future changes in population sizes and growth rates. This is essential for answering questions in areas such as biodiversity conservation and human population growth. Also population growth gives scientists insight into how organisms interact with each other and with their environments. This is especially meaningful when considering the potential impacts of climate change and other changes in environmental factors (how will populations respond to changing temperatures? To drought? Will one population prosper after another declines?).

Thank you for listening to this episode of My AP Biology Thoughts.   For more student-ran podcasts and digital content, make sure that you visit www.hvspn.com.  See you next time!

Music Credits:

  • "Ice Flow" Kevin MacLeod (incompetech.com)
  • Licensed under Creative Commons: By Attribution 4.0 License
  •  http://creativecommons.org/licenses/by/4.0/

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