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Module 9S2 Changes in Populations

Lesson 4.9.4S2

4.9.4S2 page 2

Explore

 

The Amazing Race

 

If you have a good imagination you might be able to visualize a competition being held in which all species of the planet are lined up and given the following two tasks to complete in order to win the competition:

  • Make as many offspring as possible. The offspring must survive long enough to reproduce.
  • Spread yourselves as far and wide over the planet as possible.

Each entrant is given $1000 in ATP energy currency which they can use to complete the tasks. How they spend the money is entirely up to them, but each body system employed in the quest requires more energy. If you were one of these species, what strategy would you use?

  • Would the kind of environment you’re in make a difference to your strategy? (stable vs. unstable)
  • Is it better to reproduce at biotic potential (r) or just enough to remain at carrying capacity (K)?
  • Should you attempt to improve your offspring’s survival by nurturing them, or just concentrate on producing more offspring?
  • Should you begin reproducing as soon as possible or wait until later?
  • Is it better to reproduce only once a year when conditions are good, or continually?

K-selected strategy: takes advantage of stable conditions; characterized by few offspring with much investment and nurturing to increase offspring survival

 

r-selected strategy: takes advantage of favorable conditions; characterized by early reproduction and high reproductive rate with little investment in offspring survival

Of course we know that the strategies used by organisms to survive are not chosen, but is rather the result of random mutations being acted upon by the organism’s environment; resulting in the selection of successful genotypes/phenotypes. However, 2 major life strategies have emerged: r selected strategy and K selected strategy.

 

To learn about these strategies, do the following readings and assignment:

 

Read

 

Read pages 711-713 and pages 733, 735, and 736 in the textbook.

 

Self-Check

Characteristics of r and K selected species

 

Complete the following table in your course folder using your reading assignment of p. 712-3.

 

Variablesr-selected speciesK-selected species
Life span    
Reproductive age    
# of offspring    
Growth rate is close to biotic potential (r) or to carrying capacity (K)?    
Nurturing of offspring? (care, education) of young    
Size of organism    
Stability of environment    
Show logistic growth (S curve) or exponential growth (J curve)?    

 

Check your work.