Module 9S2 Changes in Populations

Lesson 4.9.4S2

Lesson 4—r and K Selected Life Strategies

Get Focused

Consider the dandelion: a lovely yellow flower with a bad reputation. Dandelions can be seen bursting through lawns in the spring, creating color and cheer. Unfortunately, our culture considers them a weedand uses herbicides in an attempt to get rid of them before they out-compete the grass species that form our lawns. Many cultures look forward to dandelion season to harvest the dents du lion (lion’s teeth) leaves as one of the first edible species of spring, bringing vitamins and minerals after a long winter. Wind pollination occurs almost immediately after flowering, and the seed heads which look like balls of fluff, are carried away by the wind, increasing their dispersal. The entire life cycle is completed in 3 weeks ensuring reproduction is completed before frost, drought, heat, or flooding is able to prevent it. Unstable conditions require a strategy that produces as many offspring as possible, as quickly as possible, with no other investment of energy.

The beaver (Castor canadensis) only becomes fertile after 3 years. Generally only 2 young are born, and they stay with their mother for 2 years, watching and learning the skills needed to harvest trees, make dams, build lodges, and avoid predators. Though there are few young, they are highly skilled by the time they leave her and therefore have a higher chance of survival. What kind of environmental conditions would favor such a long-term investment of energy?

By the end of this lesson you should be able to answer the following focusing question: 

• What are the characteristics and reproductive strategies of r-selected and K-selected organisms?

Module 9: Section 2—Lesson 4 Assignment

 After you have completed all learning activities for this lesson you can complete the online assignment.

Bio 30 4.9.4S2 online assignment

In addition to your lesson work as listed below, any summary notes, sample problems, diagrams, charts or tables should be stored in the course folder for your teacher’s feedback and study as you prepare for exams.

You must decide what to do with the questions that are not marked by the teacher. Remember that these questions provide you with the practice and feedback that you need to successfully complete this course. You should record the answers to all of the questions and place those answers in your course folder.