1. What is competitive exclusion? Give an example.
Bell Work
What is competitive exclusion? Give an example.

2. Today’s Objectives
Students will address how populations are distributed.
Students will describe how populations are sustained over time.

3. Describing Populations
Geographic range- the area inhabited by a population
Factors that determine population range:
Abiotic- non-living factors in an organism's environment
Ie. Climatic factors, edaphic factors, & social factors
Biotic- living factors in an organism's environment
Ie. Predators, competitors, parasites
A species may not be able to expand its pop. range b/c it can’t survive the conditions in another region

4. Describing Populations
Population Density- measurement of the number of individuals living in a defined space
Example: 200 deer in 10 square Km; there would be 20 deer per square Km
Example: 40 people in 20 square units; there would be 2 people per square unit

5. Describing Populations
Population Distribution: A way in which populations are spread in an area
Uniform dispersion: Live specific distances from one another
Random dispersion: spread randomly within an area
Clumped: Individuals live close together in groups
Facilitate mating, gain protection, food resources

6. Occurs when there is fierce competition for resources or territory
Uniform Distribution
territory- physical area
Creosote bushes that live in arid Southwest show this pattern. Large, mature plants deplete soil water all around them. Seed eating ants and rodents forage near the plants, which offer cover from predators and the sun. Most seeds are devoured so seeds typically take hold only at patches where established, mature or weakened plants have died
Occurs when there is fierce competition for resources or territory

7. Occurs when individuals set up territories for feeding, breeding, and nesting

8. Few pop. live this way in nature

9. Occurs in areas of the habitat with favorable conditions for survival
Clumped Dispersion
Herds, patchy resources
Occurs in areas of the habitat with favorable conditions for survival

10. Why Clumped?
Each species is adapted to a limited set of ecological conditions- patchy in a habitat
Many species gather in social groups for survival and reproduction
Adult species don’t disperse young over a large distance

11. Random Dispersion
Random dispersion- only when habitat conditions are nearly uniform, resource availability is steady, and individuals of the pop. Don’t attract or avoid one another
occurs in habitats where environmental conditions and resources are consistent- homogenous environments
deer
Occurs when habitat conditions are nearly uniform (steady resources & organisms don’t attract or avoid one another)

12. Bell Work
Create a list that explains how a population may change in size. Explain the causes that lead to these effects.
Cause
Effect
High birth rate, immigration, increased food supply, less competition from other pop., improved climate= increase in pop. or growth
High death rate, emmigration, predation, parasitism, lack of resources= decrease in pop. or no growth

13. Today’s Objectives
Students will address how populations are distributed.
Students will describe how populations are sustained over time.

14. Population Growth Patterns
Increase in Population:
Immigration: movement of individuals INTO a population
Births: Increase the number of individuals in population
Decrease in Population:
Emigration: movement of individuals OUT of a population
Deaths: Decreases population
Population Growth Rate= (birth rate- death rate) (# of individuals)

15. Herrings lay a million eggs a year, if all the eggs hatched and survived, the entire surface of the earth would be knee deep in herring in a short amount of time. Thank goodness this doesn’t happen in a normal pop. The maximum growth rate of any type of species however is also called the Biotic potential.

16. Biotic Potential
The maximum rate of increase per organism under ideal conditions
Rate depends on the age each generation starts to reproduce, how often an individual reproduces, & how many offspring are produced
Human population biotic potential= 6% each year
Rats biotic potential= 1.5% each day
Bacteria biotic potential= 250% an hour
Biotic potential for human pop.= 6% each year (if growing at this rate, doubling in under 12 years); small biotic potential compared to rats (1.5% per day- pop. living in a warehouse could double in size in only 47 days). Bacteria are the champion producers… given certain conditions, growth rate can be 250% an hour, each bacteria divides more than once an hour.
In order to understand how pop. work, we must first look at what would happen if there were no limits on the growth of a pop.

17. Models of Population Growth
Directly determined by the amount of resources available
Exponential Growth
Logistic Growth

18. Exponential Growth
Rapid growth that occurs when a population grows under ideal conditions with “unlimited” resources
Lag phase= slow growth period
J-shaped curve
Increased birth and immigration +
Have you ever been asked a question would you rather earn 1 million dollars today or would you like to earn a penny today, see that double and earn two pennies the next, four pennies the following, then 8 etc.? Although you start out with slow growth in time you will earn over 1 million in just a month. If I was mean I’d have you guys really visualize exponential growth and what I would have you do is take a piece of graph paper and color in the first square, color in two after that, then four, you get the idea… no matter how big your piece of paper is or how big the squares are, the last turn will involve coloring the other half of the paper!
Organisms will eventually deplete their resources in the absence of predators or natural mechanisms may cause the pop. to level off and maintain equilibrium
Lag phase

19. Biotic potential for human pop
Biotic potential for human pop.= 6% each year (if growing at this rate, doubling in under 12 years); small biotic potential compared to rats (1.5% per day- pop. living in a warehouse could double in size in only 47 days). Bacteria are the champion producers… given certain conditions, growth rate can be 250% an hour, each bacteria divides more than once an hour.
What is this a picture of? Bacteria growing on agar. What is agar? A gelatinous substance taken from seaweed and it’s a food additive for bacteria growth?
Now this is a sample of e. coli and E. Coli doubles every twenty minutes however you see a point where reproduction comes to a halt and the pop. decreases.

20. Carrying Capacity
Carrying capacity- maximum # of individuals of a pop. an environment can sustain for a long period of time
in pop resources therefore less individuals are born & more may die from deficiency
When a pop. increases, more individuals compete for limiting resources.

21. Logistic Growth Model
Growth that may follow a period of exponential growth when a population’s growth slows/levels off.
Meets carrying capacity
S- shaped curve
Occurs when emigration & death exceed immigration & birth
Carrying Capacity
Time
Population
When a pop. equals carrying capacity, its growth rate=0; populations are said to undergo three distinct phases of their life cycle: growth, stability, and decline. Nearly all populations tend to grow exponentially as long as there are resources available. Stability is usually the longest phase of a
population’s life cycle. Decline is the decrease in the number of individuals in a population. The Logistic curve (also known as an S-curve) shows the effect of a limiting factor (which can be the carrying capacity of the environment).

22. Environmental Resistance
Is the combined effects of all the factors that limit pop. growth
This resistance is the force opposing biotic potential
As pop. naturally increases, environmental resistance acts to slow its growth much as friction slows a car and limits its speed

23. Factors that limit population growth
Limiting factor: this factor has the greatest effect in keeping down the size of the population
Density-dependent: factors that are affected by the number of individuals in an area (competition, predation, parasitism and disease)
Density-independent: environmental aspects that are not affected by how many individuals there are (typically abiotic like weather, natural disasters, human activity)

24. Review!!

25. Populations
Can be described by
Three Types: 1. 2. 3.
Affected by
Which can be
which are usually
Dispersion
Density
Growth Rate
Which can be: 1. 2.
Limiting Factors