Topic 4:

Why Rabbits Have So Many Babies…

Announcements:

• Lab this week!  MEET at Junction Creek Trailhead (lower trailhead by restrooms, where road turns to gravel) @ 1:40.  Bring notebooks or paper, lab handout, any field guides you might own, & be ready to look at plants.

• https://maps.google.com/maps?saddr=Fort+Lewis+College,+Rim+Drive,+Durango,+CO&daddr=Co+Rd+204&hl=en&ll=37.302597,-107.882309&spn=0.071414,0.155697&sll=37.334747,-107.91132&sspn=0.035692,0.077848&geocode=FcvGOAIdBQ-S-SFN4dmSVRhWlCkXBAAJqQI8hzFN4dmSVRhWlA%3BFduyOQIdR1uR-Q&mra=dme&mrsp=1&sz=14&t=m&z=13
   

• Beast in the Garden readings - first discussion next Week in Lab (in Field)!!
   

• Lab next week - Aquatic Foodwebs - meet at Rotary Park (gazebo) on Animas River at 1:35 (see Moodle for directions & hand-out)
   

• Odyssey essay - read for next Tuesday

Learning Goals for Day:

Ø      Understand the main patterns of population growth observed in biology, and be able to draw graphs to illustrate them

 

o       Understand the difference between exponential growth & Resource-Limited Growth (a.k.a. “Logistic” growth)

o       Know the meanings of terms in the equation:  r = ∆N/∆t

o       Be able to explain the concept of “Carrying Capacity” (K) and show its relationship with different population growth curves


 

Ø      Understand the 2 main reproductive strategies exhibited by living things

 

o       K-selected species: few, large young (“large young strategy”)

o       r-selected species: many, small young or eggs (“small egg strategy”)

o       give examples of each

o       understand the trade-off between number & size of offspring

Questions for Thought:

1. Is the carrying capacity for a given population of a species static/permanent, or can it change?  Why or why not?
   
   
   
   
   
   
    

2. Describe what r  should be for a population in the following conditions (would r= 0, negative, or positive):

   • population stable

   • population growing

   • population declining

Assess – Goals:

Ø      Draw a picture/graph showing exponential growth, & one showing resource-limited growth.

o       Where is maximum “r” on each graph?

o       Where is K ?
 

Ø      Thought question – how do birth rates & death rates relate to the term for ∆N  in the equation above? 

o       What will happen to r if birth rates increase dramatically, and death rates go down?

o       What about the reverse – lower birth rates, higher death rates?
 

Ø      Is the Carrying Capacity of an environment static or unchanging for a given species?  Why or why not?
 

Ø      Energy- &  resource-wise, what is the trade-off for animals who employ the “r” vs. the “K” strategy of reproduction?

o       under what circumstances would one strategy be better than the other?  why don’t all critters use the same approach?