Module 8
1. Module 8
1.47. Page 5
Module 8—Populations, Individuals, and Gene Pools
Lesson Summary
This lesson focused on the following questions:
- What are the different types of population growth patterns?
- How do growth patterns illustrate these types of changes over time?
In this lesson you learned to describe a population as r-selected (J curve) or K-selected (S curve). The terms are used in comparison to each other. K-selected species live close to carrying capacity, have long lifespans, are generally large in mass, reproduce later in life, and have small numbers of offspring, which they nurture. In comparison, r-selected species are growing close to their biotic potential, have short lifespans and early reproductive ages, are generally small in mass, and have large numbers of offspring with large die-off and little, if any, parental care. Furthermore, K- and r-selection are two extremes of a continuum—most species fit in between.
You have studied how the phenomena influenced by human activity, such as climate change, over-harvesting, pollution, and introduction of invasive species into foreign environments, can greatly affect populations. You have also learned that age pyramids are useful tools for predicting future populations.
Human populations were at carrying capacity for most of history. Technology has increased life expectancies and decreased infant mortality, causing the carrying capacity and population growth rates to increase exponentially. Today, due to reduced birth rates, many human populations are no longer growing exponentially, though a few are. The human carrying capacity will be influenced by growth rates, age structures, the state of the environment, and technological developments, but will likely be approximately nine billion.
Lesson Glossary
Consult the glossary in the textbook for other definitions that you may need to complete your work.
K-selected strategy: takes advantage of stable conditions; characterized by few offspring with much investment and nurturing to increase offspring survival
K-selected organisms: species that have K-selected strategies, such as longer life span, later reproductive age, few offspring, and parental care
reproductive strategy: the strategies used in reproduction to ensure survival of a species; may be r- or K-selected strategies
r-selected strategy: takes advantage of favourable conditions; characterized by early reproduction and high reproductive rate with little investment in offspring survival
r-selected organisms: species that have r-selected strategies, such as a short life span, early reproductive age, large numbers of offspring, and little parental care