Do now 02/27  What are some things that might be a result of the growth of the human population? What are some effects?  DO NOW 03/02  How do you think the east coast’s weather is affecting us on the West coast?

Human population growth? 

 Intro Human Populations

Reading  Read the article independently. We will then discuss.  There is a glossary on the last page for reference

Mind Map  Make a mind map with “7 billion and counting” in the center of your paper  You will work in teams of 3-4  7 billion people on earth leads to…

Today we will…  4.1: I can understand what human population dynamics is, its history, and why it is important  4.2: I can distinguish between exponential and logistic growth curves and elaborate on what they each represent

History of Human Pop. Dynamics  For the last 200 years, populations have grown rapidly. There are 3 major factors that explain this trend: humans have developed the ability to expand; the emergence of agriculture; and sanitation, antibiotics, and vaccines help control infections.  Humans expanding has allowed the to overtake places of varying climates  Agriculture allowed for humans to add around 2 billion people to the earth due to better access to food.  Sanitation and health improvements allowed for the control of infections and allowed for the dropping of death rates in comparison to the rising birth rates

Human Population Dynamics  Population growth today is slowing but it is still growing. As humans grow exponentially, we are testing the limits of the Earth’s carrying capacity (K) and what resources are available to us.  Developed countries, like the US grow more rapidly than underdeveloped countries, like Uganda, and as we grow we utilize more resources, take up more space, and degrade the environment further.  It is important to understand how human population growth can affect the environment and how we can best curve it, by trying to decrease birth rates.

Quick check  What are the three factors that contributed to human population growth?  Why might it be important to understand how human populations grow?

Exponential vs. logistic growth  There are currently two types of curves: exponential and logistic. We will go over both in regards to how human population relates to either one of these curves.

Exponential curves  These curves show us that the rate of growth increases at a rapid rate over time. In our case, having exponential growth in a population allows us to see that a population is continuing to grow and is not decreasing any time soon. The growth starts slowly, but the growth rapidly accelerates.  This may be due to availability of resources, lack of competition, lack of disease, availability of space. This pattern usually results when a population is FIRST introduced in a new environment.

Exponential growth  Organisms have a temporary “unlimited” amount of resources available at the start of their growth. This situation is possible, but it is NOT sustainable. Eventually over time, population growth will slow down as a result of lack of resources and other factors mentioned earlier.

Quick check  What does the exponential growth curve look like and what does it tell us?

Logistic curve  In logistic growth curves, we can see that there is a capping off point, or carrying capacity (K) where the growth stops and the population size is steady.  At this point, when an environment has reached it carrying capacity (K) and can no longer sustain more individuals in the population.  The environment has limited resources that would eventually run out, thus inhibiting the growth of a population.  Other factors such as disease, lack of space, and competition could contribute to the capping of population growth.

Logistic Curve

Quick check  What does the logistic growth curve look like and what does it tell us?  What is the difference between an exponential growth curve and a logistic curve?

Humans and Growth Curves  Humans are facing exponential growth, but the rate at which human population is expanding is DECREASING.  Logistic growth for us would represent humans exhausting all of Earth’s resources and eventually inhibiting more humans from populating. When we reach this point, there might be enough resources available to sustain human lifestyles.  Note that humans from developed countries, like the US tend to use more resources compared to underdeveloped countries, like Ghana. We have large ecological footprints that negatively impact the environment.

Quick check  What curve best represents human population growth? Why?

Active Practice  1. Describe the general trend on human population growth throughout history and name three general factors that might have contributed to the growth of the human population. Explain how the trend might be possible. Do this in 3-4 sentences.  2. Predict why birth rates might be dropping now. Use outside real-world examples or previous outside knowledge you may have. 1-2 sentences.  3. What is the real concern with the size of the human population aside from the actual numbers? Why might this be? Answer in 2-3 sentences.  4. Describe in 3-4 sentences how the United States contributes to the human population growth issue. Use any evidence presented in the text.  5. What are some ways that we have tried to curb population growth rates? Suggest solutions you might propose towards helping the population growth problem. 3-4 sentences.  6. What type of growth pattern are we following now? Explain how that is true.