Module 8 Lesson 6 - 1

Get Focused

Consider the dandelion: a lovely yellow flower with a bad reputation. Dandelions burst through lawns in the spring, producing colour and cheer. Unfortunately, our culture considers them to be weeds and uses herbicides 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 that look like balls of fluff, are carried by the wind, increasing their dispersal.

The entire life cycle is completed in three weeks, ensuring reproduction is completed before frost, drought, heat, or flooding can prevent it. Unstable conditions require a strategy that produces as many offspring as possible, as quickly as possible, and with no other investment of energy.

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

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

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