 Warm-up: (10-19-15)
*ch.5 CW/CG and rubric out for stamp!
 Read the article on Parachuting Cats.
 Answer the questions in your warm-up
 Do not copy the questions
 No complete sentences
 Remember to answer the questions on Task 5 of Turkey trouble
 Be sure to label your graphs (x and y axis) or you wont get a stamp.
 Chapter 5-5
 Population Ecology
 Goals for today:
 Contrast biotic potential and environmental resistance
 Contrast exponential and logistic growth curves
 Contrast density dependent and independent factors
 Describe stable, irruptive, cyclic, and irregular population curves
 Community or Population Ecology?
 Eastern screech owls bring live blind snakes to their nests to live with them.
 Babies grow faster and stronger with the snake present.
 Biotic Potential
 Biotic potential and environmental resistance determine carrying capacity.
 Biotic potential: pop.’s capacity for growth
 intrinsic rate of increase (r): rate of growth with unlimited resources.
 High intrinsic rate of increase means:
 Many offspring
 Reproduce early in life
 Reproduce often
 Short generation time
 What are some examples of organisms that have a high intrinsic rate of increase?
 Can a population increase its size indefinitely?
 No! there are limits…
 Limiting factors: limit pop. growth
 What are some limiting factors?
 Environmental Resistance
 Environmental Resistance: factors that limit pop. growth.
 Ex. Competition
 This is like (+,-) feedback
 Both the biotic potential and environmental resistance determine the carrying capacity.
 Carrying capacity (K):
 the max. pop. an area can sustain without being degraded
 What two factors determine carrying capacity?
 Exponential model
 Doesn’t take into account limiting factors: food, space, waste removal.
 Only accurate prediction for short period of time.
 What is the shape of a graph showing exponential growth?
 Why are the turkeys in trouble in Task 1?
 Exponential model
 Exponential model: describes a population that increases rapidly after only a few generations.
 Ex. Bacteria.
# of
indiv.
time
 Logistic model
 Accounts for limiting factors.
 Birth and death rates are not constant.
 Moves closer to carrying capacity (K)
 Logistic model
# of indiv.
time
 Region A: pop. growing exponentially
 Region B: death rate inc./birth rate dec.
 Region C:stabilizing; death rate/birth rate equal.
 Exceeding Carrying Capacity:
If you exceed carrying capacity, what are your options?
1. Move
2. Switch Habits
3. Decline in Size
The population crash will not happen right away. What is this called?
 In 1911, 25 reindeer (4 males and 21 females) were introduced onto St. Paul island.
 At that time there were no predators of the deer on the island and hunting of the reindeer was not permitted.
 By 1938, there were about 2,000 reindeer on St. Paul Island.
 Guess what happened next????
 By 1950, only ____ deer were left.
 Population Density and Population Change
 A population’s density can affect how rapidly it can grow or decline.
 Density dependent factors
 Density independent factors
 Density dependent
 Ex. Food shortage, disease
 Density independent factors: pop. reduced by a factor that doesn’t depend on pop. size.
 Ex. Natural disasters
 Competition is a density-_____ factor
 Hurricane?
 Ebola?
 Flood?
 Mudslide?
 Types of Population Curves in Nature
 Stable
 Irruptive
 Cyclic (boom-and-bust)
 Irregular
 Stable: fluctuates slightly above and below carrying capacity.
 Irruptive: explodes and then crashes to a more stable level.
 What type of feedback is seen in the crash part of this curve?
 Cyclic: fluctuates regularly
 a.k.a. boom-and-bust
 Irregular: erratic changes (possibly due to drastic changes to the habitat)
 Ex. Insect populations in severe winters
 Check for Understanding:
 1. List 2 examples of density independent factors.
 2. The logistic growth curve looks like the letter ____.
 3. Describe a stable population curve.
 4. Describe an irruptive population curve.