Question

1. what causes the population to slow down during logistic growth?
2. the maximum population an environment can sustain is affected by environmental factors that cause the population to level out or become stable. what term is used to describe this level of logistic growth?
3. propose some reasons why population growth is so rapid immediately after the lag phase in both diagrams for model 3?
4. exponential growth (diagram a) refers to the phenomena of populations that double in size every generation. if you start with a single bacterium capable of dividing every 20 minutes, how many bacteria would you have after just four hours?
5. in most natural populations rapid exponential growth is unsustainable. as populations increase, environmental resistance causes the growth rate to slow down, until carrying capacity is reached. brainstorm several factors that could be considered as environmental resistance.
6. diagram b shows that the population size fluctuates around the carrying capacity. considering what you know about interactions in the environment, brainstorm some of the factors that could cause these fluctuations. in your answer, you should relate these factors to the information from model 1.

Explanation:

1. In logistic growth, as the population size approaches the carrying capacity of the environment, resources (such as food, space) become limited. There is increased competition among individuals for these scarce resources. Also, waste accumulation and predation (if applicable) can act as limiting factors. These factors collectively slow down the population growth rate.
2. The term used to describe the level of logistic growth where the population levels out or becomes stable (at the maximum population an environment can sustain) is the carrying capacity.
3. After the lag phase (where organisms are adjusting to the environment), in both diagrams of Model 3 (assuming typical population - growth scenarios), there is usually an abundance of resources (like ample food, available space). The organisms have also acclimated to the environment, so their reproductive rate is high (if it's a biological population, there are no or few limiting factors for reproduction at this early - exponential - like growth stage after the lag).
4. First, convert 4 hours into minutes. Since 1 hour = 60 minutes, 4 hours = \(4\times60 = 240\) minutes. The bacteria divides every 20 minutes. So the number of generations \(n=\frac{240}{20}=12\). Using the formula for exponential growth \(N = N_0\times2^n\) (where \(N_0 = 1\) (starting with one bacterium)), we get \(N=1\times2^{12}=4096\).
5. Environmental resistance factors can include limited food supply (as the population grows, there is not enough food for all individuals), lack of space (e.g., nesting sites for birds, territory for animals), accumulation of waste (which can be toxic, like in a bacterial culture where waste products can inhibit growth), increased predation (more prey means more food for predators, so predator numbers may increase and control the prey population), and disease (higher population density can facilitate the spread of diseases).
6. Factors that can cause fluctuations around the carrying capacity:

• Seasonal changes in food availability (e.g., in a deer population, during winter, plant food may be scarce, causing the deer population to dip below the carrying capacity, and in spring/summer, with more food, it may rise close to or above the carrying capacity).
• Predator - prey interactions (if predator numbers increase, prey population drops below carrying capacity; then, with fewer prey, predator numbers decrease, allowing prey to rebound towards the carrying capacity).
• Natural disasters (a flood can destroy habitat and food sources, reducing the population below carrying capacity; over time, as the environment recovers, the population can return to levels around the carrying capacity).

Answer:

1. Limited resources (food, space), waste accumulation, and predation (if relevant) slow down population growth in logistic growth.
2. Carrying capacity.
3. Abundant resources (food, space) and high reproductive rate (after acclimation to the environment) cause rapid growth after the lag phase.
4. 4096.
5. Limited food, lack of space, waste accumulation, predation, and disease.
6. Seasonal food availability (e.g., deer - food supply), predator - prey interactions (e.g., wolves - deer), and natural disasters (e.g., flood - habitat/food for a population).