My AP Biology ThoughtsUnit 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,...