Populations can be limited by abiotic factors like temperature, space, and food availability. A population's size is determined by its habitat's carrying capacity, which is the maximum population it can sustain indefinitely without degradation. For example, if food becomes scarce it can limit a raccoon population from growing further. In an activity where students gather different colored "food" items as raccoons, some raccoons faced limitations like poor health that prevented them from obtaining a balanced diet, demonstrating how factors in the environment can impact population growth and survival.

1. Limiting Factors in an Ecosystem

2. Several Abiotic Factors Can Limit
Population Growth
 Limiting factor principle
• Too much or too little of any abiotic factor can
limit or prevent growth of a population, even if
all other factors are at or near the optimal
range of tolerance
• Directly relates to:
 Carrying Capacity (K)
• The maximum population of a given species
that a particular habitat can sustain
indefinitely without being degraded
(we will return to this concept in Chapter 5)

3. Examples of Limiting Factors
 Temperature
• Animals have a “thermal range” in which their bodies
work
• Digestion & Metabolism
• Reproduction
• Locomotion (escaping predators)
• Foraging (finding food)
 Space
• How many organisms can physically occupy an area?
 Food
• Is the environment able to support an infinite number of
organisms?

4. Range of Tolerance for a Population
of Organisms
INSERT FIGURE 3-10 HERE

5. Temperature of a Scorpion…
even invertebrates have limiting
factors

6. Raccoon Activity
 Objectives:
• Define a major component of habitat
• Identify a limiting factor
• Recognize the importance of a suitable habitat and
limiting factors
 Methods
• Students will ‘become’ raccoons to look for
components of a habitat

7.  Background:
• Since raccoons are omnivores and eat a variety
of food, each color of paper represents a different
food item
• Everyone will get a paper bag that represents the
raccoon’s cache (stash of food hidden by an
animal to be used at a later date, i.e. winter)
• “Food” (paper) will be scattered about in a “forest”
(open area)
Raccoon Activity

8.  Procedure:
 Raccoons must walk through the forest
 (raccoons do not run with their food)
 Gather food
 Hide it in the cache ONE AT A TIME!!!!
 You cannot carry more than one food item at a time
 Other raccoons can steal from your cache
 Do not announce when you do this, raccoons do not make
it known when they are stealing one another’s food!
Raccoon Activity

9.  Here’s the catch:
• Not all raccoons are healthy…
• You will be randomly assigned a raccoon ‘history’
and must it out while gathering your food
Raccoon Activity

11. Raccoon Activity
 BROWN- nuts (acorns,
walnuts, hickory nuts)
• 25% of diet
 PURPLE- berries & fruits
• 25% of diet
 YELLOW- insects (grub,
larvae, ants, termites)
• 15% of diet
 RED- meat (rodents,
amphibians, reptiles,
birds, eggs)
• 15% of diet
 GREEN- plants (leaves,
grasses, herbs)
• 20% of diet
 BLUE- water

12. Summary
 Did all raccoons get enough nutrients to
survive?
 What are the limiting factors?
 How does this affect the survival of each
animal?
 What does this tell you about carrying capacity?